# 0.50 Browning MG and it's descendnats for 'other' air forces?



## tomo pauk (Apr 30, 2015)

The well known heavy Browning was a prime weapon on US-produced combat aircraft of ww2. How good/bad would it be for other air forces, if adopted just pre-war? How about further developments of the system, like the Japanese Ho-5 20 mm cannon, or just necking out the cartridge so HE shell might be introduced (not unlike what Soviets did with their slightly bigger 12.7mm)?


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## buffnut453 (Apr 30, 2015)

What date are you selecting as the start of the war?


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## tomo pauk (Apr 30, 2015)

In an Euro-centric way: 1st Sept 1939.


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## Shortround6 (Apr 30, 2015)

Ok, we have gone over some of this before. The Browning .50, like some other things, was evolving/changing during the war. Cycle rate rated changed from 600rpm (or under) for free firing guns to 800-850rpm in 1940. Apparently not a big/difficult change. But which air force gets which guns pre-war? the slow firing or the fast firing? The gun it self seems to have been fairly reliable but many installations were not. It _might_ have had trouble with belt pull (how much weight of ammunition belt it could pull or lift.) Some American turrets got electric motors to help move the belts and these motors were later used in field modifications in P-51Bs and Cs. P-51Ds didn't use them (?) and P-40s/P-47 and Navy planes didn't. but moving belts in wings with ammo the same height as the gun is not the same as trying to lift the belt from storage boxes beneath and seated mans feet in a top turret. 

Necking out the cartridge takes a lot of planning and investment for not a lot of return. The American cartridge was 20.3mm across the base in front of the rim vs 21.8mm for the Russian round. Chances of using a 20mm projectile from the American case is about zero. It means you have design all new 17-19mm projectiles and fuses and not using adapted parts/projectiles even in testing. It also puts you up against the the cube law for projectiles. Given a similar shape changing the caliber of the projectile will change it's weight by the cube of the diameter. as a rough guesstimate an 18mm projectile will weigh about 73% as much as a 20mm projectile. Of course 20mm projectiles ranged from 79 grams to 134 (or more?) so you have to pick and choose carefully. The German 15mm HEI projectile weighed 57 grams. 

For some air forces you have to balance out the weight of the gun and ammo ( one .50 round weighed about 5 times what rifle caliber ammo did) against what engines they had available. A lot of the early American aircraft with 1000-1200 engines suffered from being saddled with too much weight of guns and ammo. 

The Gun was made by FN in Belgium Pre-war and they may have gotten a higher rate of fire out of it. Considering the trouble the Americans had getting it to 1200rpm any claims of prewar FN guns firing that fast _in service_ must be viewed with suspicion. 

Scaled down to take the British/Italian/Japanese 12.7mm round it might have done fairly well for some nations. Scaled up it might also have done OK. Japanese had quality control problems and material shortages and the Browning didn't tolerate either one very well. 
The original 1917 had to be modified to the 1917A1 when it turned out the receiver wasn't quite strong enough (perhaps due to substandard material or heat treatment ?) 





The "saddle" or reinforcing on the lower receiver was not present on the original 1917 guns. 

we start getting into 'what ifs' regarding materials and hypothetical rates of fire.


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## tomo pauk (Apr 30, 2015)

I've picked the BMG not to start another 'cannon vs. HMG debate', but rather some of it's points that made it suitable for aircraft armament. Eg. it was one of the (or the)most powerful belt-fed guns until Shvak came along, yet light enough so multiple guns could be carried even with fighters with 1000-1200 HP onboard. 
A cannon of 18mm should give us, say, an 80 g HE shell, 70 g Mine shell, with MV of 700-750 m/s? The RoF would've probably start at around 600 rpm, increase of up to 850 rpm was for the Japanese Ho-5 cannon, though Wikipedia gives 950?



> For some air forces you have to balance out the weight of the gun and ammo ( one .50 round weighed about 5 times what rifle caliber ammo did) against what engines they had available. A lot of the early American aircraft with 1000-1200 engines suffered from being saddled with too much weight of guns and ammo.



The P-39 might've benefited with 3 'cannoncinos' only; synchronization kills Rof down to 500, so it would be 800 + 1000 rpm for the trio. Maybe adding another one synchronized, between the two? Wing guns ammo deleted, of course. The P-38 with 5, P-47 with 6, remainder of S-E fighters with 4?
In case British decide to make the 18mm, 4 for Hurri and Spit? Or 2 of those, plus 4 MGs in time of BoB? 
Germans - 2 for Bf 109E (HMG for the earlier versions), the 3rd added in central position? 4-6 for the Fw 190?

Re. Ho-5: looks like the gun was okay from get-go:


> Claims that the ammunition of the Ho-5 was downloaded to solve reliability problems appear to be incorrect. According to Col. Okamoto, the gun was designed for a muzzle velocity of 750 m/s, and both wartime and post-war US source specify it as 2400 to 2500 fps, i.e. 730 to 760 m/s. Col. Okamoto does not mention downgrading of the ammunition. (Ted Bradstreet)


From here.


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## Shortround6 (Apr 30, 2015)

It kind of depends on when and what weight (and money) you are willing to devote to armament.

A MK II Spit carried about 430lbs. 254lbs for the eight .303 Brownings. 31.75lbs per gun. that is from a Spitfire Weight and load chart. 2800 rounds (350rpg)weigh 186lbs or 6.64lbs per hundred. 

An F4F-3 Wildcat had four .50 cal guns that weighed 286lbs. .50 cal ammo weighed _about_ 30lbs per hundred depending on bullet mix and links. _Normal_ load was given as 360lbs or about 300rpg. Overload was 516lbs of ammo or 1720 rounds (430rpg).

If you want to keep the Sptifire's weapon load you have about 130rpg for four .50 cal guns. 

A Spitfire with 2 belt feed cannon and four MGs had an armament weight of 650lbs (MK Vc and later) or just about what the Wildcat with four guns and 300rpg had.

These weights do not include ammo boxes/trays. some mounts/local reinforce, gun controls and gun heating arrangements.

For the early 109s the Browning weighs within a KG of what the MG FF did. Replacing it one for one seems easy enough, question is the ammo. It _appears_ (open to correction) that 60rounds plus drum went about 20kg for the MG FF or 44lbs, rounding up gives us about 150rpg for the Germans to use in the wings of the 109 if they keep the weight about the same. Do the Germans get the 600rpg guns or the 800rpm guns? Granted the 109E-3s can loose about 500 rounds per gun from the cowl guns and not hurt much of anything but that only saves about 60lbs. Enough for another 100 rounds for each wing gun. 

The Americans and Soviets never came up with exploding ammo (or even high capacity incendiary ammo) for their high velocity 12.7mm guns. I am not sure why. Germans, Italians and Japanese did for their lower velocity 12.7-13mm guns. Japanese had trouble with prematures. It could be they didn't want to bother with fuses that small. It could be that the higher velocity and higher pressures acting on the base of the projectiles required stronger construction, cutting down on an already low HE content. I don't know. 

According to the chart on Tony Williams web site the the six gun P-40 had just 12 KG less armament than a Hawker Typhoon with four 20mm cannon and 22kg more weight than a Fw 190A-4 with two 7.9mm, two 20mm MG 151s and two 20mm MG FF/ms and about 100kg less than a FW 190A-8 with two 13mm guns and four 20mm MG 151s. I would note that there are a few mistakes in the chart so until somebody adds the weights up to double check we may want to take it with a grain of salt. 

The .50 was cursed not only with it's own weight but it's heavy ammo. A single round goes about 112grams compared to the 162 grams to over 250grams for 20mm ammo. Unfortunately the only _common_ 20mm round that weighs twice waht a .50 cal round does (or a bit more) is the Hispano. The German, Italian and Japanese 12.7-13mm rounds were about 70-75% of the weight and some of the lighter 20mm cannon rounds were only about 65% heavier. 

The American .50 also does not play well with others  
While it is a pretty good ballistic match for the 20mm Hispano it it more of a mismatch for most other countries guns. It's high velocity and streamline bullet means it's time of flight is going to be rather different than most other peoples 20mm guns and RCMGs.


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## Greyman (Apr 30, 2015)

Shortround6 said:


> The Americans and Soviets never came up with exploding ammo (or even high capacity incendiary ammo) for their high velocity 12.7mm guns. I am not sure why. Germans, Italians and Japanese did for their lower velocity 12.7-13mm guns. Japanese had trouble with prematures. It could be they didn't want to bother with fuses that small. It could be that the higher velocity and higher pressures acting on the base of the projectiles required stronger construction, cutting down on an already low HE content. I don't know.



I imagine they came to the conclusion that the effectiveness of an explosive .50-calibre round wasn't worth it. Using the British 'de Wilde' incendiary was a much better choice in my opinion. 

Not sure what the Russians used.


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## kool kitty89 (Apr 30, 2015)

Shortround6 said:


> Scaled down to take the British/Italian/Japanese 12.7mm round it might have done fairly well for some nations. Scaled up it might also have done OK. Japanese had quality control problems and material shortages and the Browning didn't tolerate either one very well.


The lighter Japanese Army adaptation is indeed interesting, though so is the heavier 13.2 mm Japanese Navy one, and more so the sheer breadth of developments into cannons the Japanese Army managed. It shows a potential for the basic design that everyone else (even its original designers) apparently missed. (though at one time on the forums here there was mention of a .60 cal US adaptation of the browning -not the T17 MG 151 copy- but I never got more definite details on this, though the mention seemed to imply it was a direct adaptation of the existing gun and ammunition case necked out to .60 cal and presumably firing at a somewhat lower velocity)

Regardless of that, the american .60 cal anti-tank rifle round used on the T17 would have made sense as the basis for a heavier gun or 20 mm ammunition as well. (particularly had the Hispano not been adopted) The 23 mm madsen ammunition the US was interested in pre-war would have been very interesting to see adapted to a browning derivative as well. (as would the 37 mm ammo of the Browning M4 cannon, given what the Japanese managed with a 37 mm BMG adaptation, the 23 mm probably would have been more useful though, including on the likes of the P-38 and P-39)

British investing in adapting the browning to larger caliber would have made sense too, perhaps with one or more of the drum-fed oerlikon guns kept as alternatives. (the FFF and FFL were both attractive for wing mounting on fighters ... granted, the British historically only tested the heavier FFS which manifested similar problems to the Hispano)


British and Americans had limited interest in synchronized guns, and the Browning (at least beyond .30 cal) was far from the best performing in this regard anyway, but it at least /could/ be synchronized, unlike the Oerlikon guns or Hispano. (the latter technically could have been modified to do so, unlike the oerlikon, at least if electrical priming had been adopted)




tomo pauk said:


> The P-39 might've benefited with 3 'cannoncinos' only; synchronization kills Rof down to 500, so it would be 800 + 1000 rpm for the trio. Maybe adding another one synchronized, between the two? Wing guns ammo deleted, of course. The P-38 with 5, P-47 with 6, remainder of S-E fighters with 4?
> In case British decide to make the 18mm, 4 for Hurri and Spit? Or 2 of those, plus 4 MGs in time of BoB?
> Germans - 2 for Bf 109E (HMG for the earlier versions), the 3rd added in central position? 4-6 for the Fw 190?
> 
> ...


From most of what I've seen on the topic, the Japanese Browning adaptations would have indeed progressed more smoothly (and been more reliable) if not for their material and quality control shortcomings. (ie if similar developments had taken place in the US or UK, for example)

A 15-20 mm 'light' machine-cannon derivative able to be mounted in most cases the existing .50 BMG could would be very useful (something moderately heavier than the existing .50 cal, say close to the MG 151).

Aside from that the above comments on 37 and (especially) 23 mm ammunition would be relevant, possibly practical for wing mounting a well in the 23 mm case, but certainly for nose mounting in the P-38 and P-39.





Greyman said:


> I imagine they came to the conclusion that the effectiveness of an explosive .50-calibre round wasn't worth it. Using the British 'de Wilde' incendiary was a much better choice in my opinion.
> 
> Not sure what the Russians used.


With anything below 15 mm, the consensus generally seemed to be that HE rounds were ineffective given the limited capacity and space occupied by fuzing. (with mine shells, the 13 mm german ammunition might have been an exception, particularly with HE/I loadings broadening effectiveness) There's the possibility of using unfuzed rounds filled with sensitive high explosive intended to detonate on contact (I believe some .30 cal ammo used PETN filler for this reason), but incendiary fillings seemed to be considered more effective there too. (particularly incendiary fillings that also had low-explosive impact properties -various flash-powder like aluminum/magnesium + oxidizer compositions that acted as contact/impact explosives and incendaries, though I believe De Wilde used nitrocelulose to similar effect)


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## Greyman (Apr 30, 2015)

'De Wilde' was magnesium/aluminum alloy (50%), barium nitrate (50%)


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## kool kitty89 (May 1, 2015)

Greyman said:


> 'De Wilde' was magnesium/aluminum alloy (50%), barium nitrate (50%)


OK, that's what I'd thought ... barium nitrate flash powder composition that ignites/explodes on impact. What threw me was wiki's article detailing the Mk.VI incendiary as using nitrocellulose Incendiary ammunition - Wikipedia, the free encyclopedia it seems trying to refresh my memory on the subject misinformed me as that article only lists the failed Mk.VI and not the Mk.V or Mk.VII using Dixon's barium nitrate design. (the Mk.VII is the one I particularly remember as it's rather well illustrated in the Incendiary B Mark I.z .5" vickers round)

Untitled Document

I'd imagine that high capacity .50 cal Vickers round would have been popular on aircraft had the british adopted something akin to the Ho 103.


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## Greyman (May 1, 2015)

The Mk.VI round wasn't failed at all. That was the initial 'de Wilde' incendiary that made it just in time for the Battle of Britain and was _highly_ sought after by pilots.

The Mk.V is probably what you are referring to. I can't recall details on it - in any case the design either wasn't adopted or saw very, very little service.

The VI was Dixon's "de Wilde" design.
The British gave Dixon's design to the USA, who improved and simplified the design, and this in turn was copied by the British to create the Mk.VII.

All British ammunition used in aircraft used nitrocellulose propellant, and this is probably where the wiki contributor became confused.


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## tomo pauk (May 1, 2015)

FWIW, the book 'The machine gun' by Chinn can be downloaded. More here.


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## kool kitty89 (May 1, 2015)

Greyman said:


> The Mk.VI round wasn't failed at all. That was the initial 'de Wilde' incendiary that made it just in time for the Battle of Britain and was _highly_ sought after by pilots.
> 
> The Mk.V is probably what you are referring to. I can't recall details on it - in any case the design either wasn't adopted or saw very, very little service.


Correct, the Mk.V was a fuzed explosive/incendiary round deemed too complex and costly to mass produce.
https://sites.google.com/site/britmilammo/-303-inch/-303-inch-incendiary




> All British ammunition used in aircraft used nitrocellulose propellant, and this is probably where the wiki contributor became confused.


All military guns/cannon in the modern world were using smokeless powder by that time, the British mostly using Cordite, a double-base propellant with a high fraction of nitroglycerin combined with nitrocellulose and a small portion of petroleum jelly. Alternate loadings seem to have included granulated single-base nitrocellulose powders, presumably with some sort of stabilizing agent.

I could see it being the source of confusion, but it's still a pretty major oversight. (though the actual composition used in Mk.VI and VII rounds seems to be a bit uncommonly cited as well) Though I suppose it could have been further confused by notes regarding transition from cordite to single base nitrocellulose propellants.

Ironically, the Barium Nitrate article on wiki gets it right: Barium nitrate - Wikipedia, the free encyclopedia


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## tomo pauk (May 2, 2015)

> Shortround6 said:
> 
> 
> > ...
> ...


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## kool kitty89 (May 3, 2015)

tomo pauk said:


> The low 'bang-for-buck' of exploding .50 ammo is surely an issue, eg. the Germans didn't bothered much even with MG 151 and went fast to the 20 mm variant.


I think it was also partially due to the MG 151 being simple to adapt to 20 mm and the 15 mm cartridge was powerful enough to allow for a reasonably high velocity for a 20 mm projectile as well. (and the 20 mm mine shell was already in production AND more effective than a 15 mm variant would be)
They did later adopt 13 mm HE or HE/I loadings, and those seemed to be more effective than the Italian attempts at 12.7 mm HE rounds. (perhaps due to the slightly larger caliber and experience with thin-walled HE shells?)




> Compared with Hispano II (50 kg), the weight of two '18mm' should be ~60 kg. Where 150 rds of Hispano ammo are carried, 250 rds of the 18mm might go instead (weight-wise). The MV should be lower for the proposed gun, but RoF should go to 3200 rpm for 4 of them, vs. 1200-1300 for the Hisso II. Hispano would fire a more powerful shell, 130 g vs. ~80 g.
> For the Germans, the proposed gun would've been fitted more easily in the wings of the Bf 109 than a 'full power' 20 mm cannon, and contrary to the MG FF it would be belt fed. That would also allow to get rid of the cowl LMGs/HMGs.
> Since the gun muzzle would be either not protruding, or just a little bit protruding, that would cut a drag a bit vs. a muzzle sticking out a foot or like.


With the dimensions of the .50 BMG cartridge, an 18 mm projectile might manage similar or maybe higher velocity than a MG-FF or Oerlikon FF round, but likely less than the FFL, perhaps also similar to the under-loaded cartridges used on the Ho-5. (so likely in the low 700 m/s range for a 100 g projectile)

Using the existing cartridge case dimensions and similar propellant loadings to what the existing .50 cal browning already tolerated would have simplified conversion, but at very least you'd gain weight due to the larger barrel. (same case for the IJN's 13 mm Type 3 using the 13.2 mm Hotchkiss round)

Adopting the 13.2 mm Hotchkiss ammunition itself might have been more attractive for many given its existing production and supply while still having somewhat higher capacity for chemical filler) Any larger calibers would mean new/unique ammunition being produced, but with the .50 BMG parent case there'd certainly be room for some attractive possibilities in the 15-18 mm range as well.

And also bear in mind that you'll be using a weapon that's significantly heavier and with heavier recoil than the Oerlikon FF -due both to the ammunition and recoil smoothing of the API blowback mechanism. (but the belt feed and potential -albeit slow- synchronization abilities would be advantageous) In fact, they'd be heavier than the FFL as well, perhaps not in recoil and likely faster firing, but heavier weapons at least.

The larger, heavier barrels with the slower muzzle velocity and lower rate of fire would probably mean considerably longer barrel life than the existing .50 M2 browning, however.


A .70 caliber round would be just shy of the 18 mm figure (17.78 mm), but for compromise between overall ballistics and projectile size, something in the .60 cal range (15.24 mm) seems like it'd make a lot of sense. In the case of the British, aside from the idea of using a lightened browning chambered for the .5 vickers round, developing a new .60 cal heavy round based on the .50 BMG would have been interesting given it should have fairly similar ballistic performance to the .303 as well as the .50 vickers round. (using a mix of all 3 types of ammunition for varying applications may have made sense as well and avoid the mismatch the .303 and Hispano suffered along with the difficulties in coping with the high weight, and powerful recoil of the Hispano -along with the drum feed of the early Hispano marks and Oerlikon guns)


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## Shortround6 (May 3, 2015)

Ok, just so we are somewhat on the same page.






From Tony Williams website. CANNON, MACHINE GUNS AND AMMUNITION

Please note that *if* you keep the same receiver length (a quick conversion) you are pretty much limited to the same cartridge overall length. If you significantly increase the projectile diameter, you have to shorten the cartridge case length and powder/propellant space. Please note that the Russian 20 X 99 and Japanese 20 X 94 use light (short) projectiles of 'standard' type. ONLY the Germans used the thin wall mine shell. The process of manufacturing the mine shell, while the concept is not difficult the actual execution is, was notable enough that the company's trademark symbol is a reference to the process. It is a similar process to making brass cartridge cases. Doing it in steel is a lot more difficult. Also please note that most cases taper, this aids extraction. Totally straight cases can cause problems and the higher the pressure the more problems. The Blow back guns usually operated at lower pressures than the locked breech guns.


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## merlin (May 3, 2015)

I wonder how capable the Belgian built Hurricanes would have been had they been built in time - as there were to be armed with four 12.65 mm Browning guns?


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## tomo pauk (May 3, 2015)

kool kitty89 said:


> I think it was also partially due to the MG 151 being simple to adapt to 20 mm and the 15 mm cartridge was powerful enough to allow for a reasonably high velocity for a 20 mm projectile as well. (and the 20 mm mine shell was already in production AND more effective than a 15 mm variant would be)



Agreed pretty much.



> They did later adopt 13 mm HE or HE/I loadings, and those seemed to be more effective than the Italian attempts at 12.7 mm HE rounds. (perhaps due to the slightly larger caliber and experience with thin-walled HE shells?)



Hmm - while the MG 131 was out of question to receive the HE shell developed for the 15 mm cannon (body diameter was 17.1 mm at the widest part), the Italian Breda might be worth a try, with body diameter of 18.4 mm.



> With the dimensions of the .50 BMG cartridge, an 18 mm projectile might manage similar or maybe higher velocity than a MG-FF or Oerlikon FF round, but likely less than the FFL, perhaps also similar to the under-loaded cartridges used on the Ho-5. (so likely in the low 700 m/s range for a 100 g projectile)



Granted, the Ho-5 wasn't that a powerful (79g shell at 750 m/s), but I don't think it was under-loaded. Please check out the quote in post #5 here.
For the 18mm, I agree that it should be around 700 m/s for the 100g shell, though I'd rather have an 80 g at 750+ m/s.



> Adopting the 13.2 mm Hotchkiss ammunition itself might have been more attractive for many given its existing production and supply while still having somewhat higher capacity for chemical filler) Any larger calibers would mean new/unique ammunition being produced, but with the .50 BMG parent case there'd certainly be room for some attractive possibilities in the 15-18 mm range as well.



My idea was to either push the base .50 cartridge up to the biggest size of the shell that is practically possible, or to come out with a belt fed 20 mm cannon that is lighter than MG 151/20, let alone Hispano. The 17-18mm exploding ammo was well within the scope of any major armament/ammo producer in the world, even in late 1930s.



> And also bear in mind that you'll be using a weapon that's significantly heavier and with heavier recoil than the Oerlikon FF -due both to the ammunition and recoil smoothing of the API blowback mechanism. (but the belt feed and potential -albeit slow- synchronization abilities would be advantageous) In fact, they'd be heavier than the FFL as well, perhaps not in recoil and likely faster firing, but heavier weapons at least.



Oerlikon FF was probably the lightest recoiling gun, so comparing with it does not mean much. It would've recoiled less than Hispano or MG 151/20, that were frequently installed in or under fighter's wings.



> A .70 caliber round would be just shy of the 18 mm figure (17.78 mm), but for compromise between overall ballistics and projectile size, something in the .60 cal range (15.24 mm) seems like it'd make a lot of sense. In the case of the British, aside from the idea of using a lightened browning chambered for the .5 vickers round, developing a new .60 cal heavy round based on the .50 BMG would have been interesting given it should have fairly similar ballistic performance to the .303 as well as the .50 vickers round.



 Trying to have fighters with homogenous batteries - 4 light cannons, no HMGs.



> (using a mix of all 3 types of ammunition for varying applications may have made sense as well and avoid the mismatch the .303 and Hispano suffered along with the difficulties in coping with the high weight, and powerful recoil of the Hispano -along with the *drum feed of the early Hispano marks* and Oerlikon guns)



Bolded part is one of main benefits of the BMG - it was belt fed from the get go. The significantly lighter weight is another (both for gun and for ammo), and should remain so even when modified for a bit more heavier projectile.


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## Koopernic (May 3, 2015)

The 0.5 inch Browning is likely to have been unattractive for many air forces.

Those air forces operating pre war designs such as the Me 109, Spitfire or the Russian fighters in particular had small aircraft with limited armament options. 

The 20mm canon was the only way these aircraft could gain significant fire power as fitting enough 0.5 inch browning's wasn't practical due to the limited armament stations possible. The Soviets did quite well with motor canon, 20mm cowling guns, and wing root mounted guns and likely suited some other oddities such as wooden wings.

The MG131 was designed around the concept of creating a compact 13.2mm gun that could directly replace rifle calibre guns. 

A M2/0.5 inch browning in many cases would not have fitted, probably not in the Me 109 cowling stations or the more streamlined or smaller German turrets.

The MG131 seems to have achieved its objective of replacing those guns while providing the destructive capability that had been lost to rifle calibre machine guns as armour increased.

Perhaps the Browning might have fitted easily in the wing stations of the Me 109 without the fitting gondolas but if that was the case the MG131 could have been fitted anyway.

I'd argue that the Spitfire might have done well with its 8 x 303 Browning's replaced by 8 x MG131 type guns.

Where the Germans might have benefitted from a 0.5 inch high velocity guns is in the commanders station of their tanks. The gun might have fitted there and given the problem the Germans had with air attack would surely have been a far more serious threat to VVS and allied aircraft than the traditional MG34 they used.

Explosive rounds were issued by the Luftwaffe on rifle calibre guns, their purpose was as a strike indicator. Because the Communist Soviet Government hadn't resigned the Hague Conventions or the Geneva conventions they started using explosive rounds in snipers guns and so these Luftwaffe rounds found themselves used by snipers on the Eastern front by the Heer as well.

One advantage of an explosive round is self destruct ability. The 20mm C38 round used by German FLAK had a self destruct. It's likely the MG151/20 and MG131 also had a self destruct ability. This is useful when you are firing above your own troops and population. Falling rounds was a big killer of civilians.


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## Shortround6 (May 3, 2015)

Please look at the photograph again. For either the German 15mm shell or the Russian 20mm shell to fit the over length of the .50 cal Browning without lengthening the receiver you would have to cut the case back to the shoulder area (cut the neck off) and then for a new neck even if slight. This will have a significant impact on powder space. Both of these projectiles (and in in fact most projectiles) will extend to the base of the neck and many will extend to the base of the shoulder.

As an indication of what can happen with long projectiles extending into the powder are you have the German MG 151/20 ammo. Using a 'standard' type 115gram projectile (base in the shoulder area) it had a MV of 710m/s, switching to the M-Geschoss 92 gram projectile with the base in pretty much the same area the MV increased to 800m/s. Using the extra long 105 gram MX-Geschoss projectile with the extra length going into the powder space, the MV fell to 640ms/s. 

Trying to use big bore projectiles in the German and BIJ (British-Italian-Japanese) 12.7mm runs into the same problem, they all used shorter (lighter) bullets than the American and Russian ( and French)12.7-13.2mm machineguns to begin with. Tring to use longer projectiles in the same over all round length cuts into the powder space. depending on projectile, it could cut in a lot. 

Then you are back to diminishing returns, if you just scale down the design a 15mm fuse won't cost 75% (or even less) than a 20mm fuse. while you save on materiel you don't save on number of parts, you don't save much on machine time and you don't save on assembly time. Same on the cost of the whole projectile, materiel costs are down but labor cost won't follow in proportion. 

While any major company or country _could_ have made sub 20mm ammo it starts to become why? The ammo won't be that much cheaper per round. Most 20mm rounds of 115-30 gram projectile weight could deliver around 10 grams of HE. Some delivered less because they used the rear 20mm of a 80-90mm long projectile to hold a tracer element. The fuse used up 20-25mm of the front of the projectile. 
The German 15mm 57 gram HE held 2.8 grams of HE but that was due not only to the small size but the fitting of a tracer element. Even without the tracer you were going to be very lucky indeed to get to 5 grams of HE. Needing two 15-16mm shells to deliver the same amount of explosive as a 20mm shell tends to skew the cost effectiveness. The Russian 20mm 97 gram shell held 6.1 grams of HE but was only 58mm in length, since it's fuse sucked up about the same 20-25mm as other peoples fuses this didn't leave much room for the HE even without the tracer. This points to not trying to use _short_ 15-18mm projectiles in small cases to keep overall length down. 

If you have to do a major modification to the gun (lengthen the receiver, bolt and bolt travel or make the bolt significantly larger in diameter) you might as well design a new case to do what you want rather than futz around trying to use old cases to save the case making tooling. That tooling will wind up being the least expensive part of the whole deal if you make a lot of ammo, as it wears out and needs replacing (the drawing dies and swages ) anyway.


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## Shortround6 (May 3, 2015)

Koopernic said:


> The 0.5 inch Browning is likely to have been unattractive for many air forces.
> 
> The MG131 was designed around the concept of creating a compact 13.2mm gun that could directly replace rifle calibre guns.
> A M2/0.5 inch browning in many cases would not have fitted, probably not in the Me 109 cowling stations or the more streamlined or smaller German turrets.
> ...



The German MG 131 was able to replace the 7.9mm guns one for one on a somewhat limited basis. While the gun may have fitted volume wise the ammunition feeds and empty case and link disposal was a bit harder. You also had a weight problem, while not as bad as trying to stick in .50 cal Brownings an MG 131 weighed about 40% more than a MG 17 and it's ammo weighed about 3 times a much per round. 300 rounds of 7.9 weighing about the same as 100 rounds of 13mm. You may wind up in a bind depending on how long you want the guns to fire. 109E-3 with 1000rpg has plenty of weight and volume to swap off. 109s with engine mounted guns cut the cowl guns to 500rpg and have a lot less weight/volume to play with. 
The wing gun question gets rather interesting. The 20mm MG FF cannon weighed 28kg (bare gun) vs 17kg for the MG 131 and the 20mm ammo weighed 182 grams per round (no Mine shells) or about 2.5 times what a 13mm round did. 
The MG 131 fires about twice as fast as a MG FF did so you need twice the ammo to get the same firing time. The Projectiles were over 3 times lighter and carried roughly 1/3 the amount of HE, this assumes that the MG 131 is using 100% HE and so is the MG FF, but roughly you need 3 times the number of rounds to do the same damage. Granted you have the weight of the drums but weight of the links is not figured in either.

Using a .50 cal Browning means the machine gun actually weighs more than the cannon (by one kg for a bare gun) but the ammo weight really skyrockets. 

Due to weight the Spitfire (at least until the MK V) wasn't going to use eight MG 131s or HO-103s (British shrunk .50 cal Brownings) even if they would "fit" in the gun space/s. The guns alone are 70-120% heavier and the ammo is even a bit heavier than the MG 131 ammo. The .303 ammo is about 30% of the weight of the British 12.7 ammo. Keeping 300 rounds per gun of the heavier ammo would have added around 140KG to the planes loaded weight just for the ammo. 



> Where the Germans might have benefitted from a 0.5 inch high velocity guns is in the commanders station of their tanks. The gun might have fitted there and given the problem the Germans had with air attack would surely have been a far more serious threat to VVS and allied aircraft than the traditional MG34 they used.



This is an argument that went on long after the war, The German Army NEVER went to the .50 cal gun for AA work from tanks even as a member of NATO ( and a lot of NATO countries agreed with them). .50 ammo tales up a lot of room inside the tank, a pintle mounted .50 cal isn't really all that effective (it bounces around a lot) and the Americans fired hundreds of thousands of rounds of .50cal ammo for each plane brought down. 




> One advantage of an explosive round is self destruct ability. The 20mm C38 round used by German FLAK had a self destruct. It's likely the MG151/20 and MG131 also had a self destruct ability. This is useful when you are firing above your own troops and population. Falling rounds was a big killer of civilians.



This could very well be why most HE ammunition for aircraft cannon was HE-tracer. Many designs used a passage way from the tracer compartment to the HE compartment with some sort of delay component to act as a self destruct mechanism. As the tracer burnt out it ignited the delay element which then burned into the HE compartment to detonate the shell.


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## Piper106 (May 3, 2015)

I think for the British and/or Allies, a better track would have been to dig out of mothballs the plans for the WW1 era Vickers rifle caliber machine guns rechambered to fire the 11mm Gras round. A scaled up to 11mm version of .303 Mark VI or Mark VII incendiary round would have quite unpleasent on the receiving end. 

The guns themselves would have been just about the same size and weight as the rifle caliber versions, the only downside would have been the ammo, which would have been heavier and larger than .303 or 30 caliber rounds. 

Would have been a interesting prospect for the 1939 to Battle of Britian era in Europe. Against the Japanese air forces with their reliance on unprotected fuel tanks, the 11mm Gras Vickers might have been effective well into 1943.


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## Shortround6 (May 3, 2015)

TANSTAAFL

The other downsides is that the bullets were much lighter than the small 12.7-13mm machine gun bullets ( 17.5 grams vrs 34-38 grams) and the muzzle velocity was 610 m/s. The kinetic energy wasn't much different than the .303. Not as good at going through armor or heavy structure, has a longer time of flight making hitting harder. It's ONLY advantage was it's higher payload of incendiary material and that might pale in comparison to the small 12.7-13mm machine gun ammo. 

Add in that the British _NEVER_ used a Vickers gun where a crewman (or pilot) could not get to it (wings, solid nose, rear of nacelles, etc) and the idea really doesn't hold up.


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## kool kitty89 (May 3, 2015)

Shortround6 said:


> Please note that *if* you keep the same receiver length (a quick conversion) you are pretty much limited to the same cartridge overall length. If you significantly increase the projectile diameter, you have to shorten the cartridge case length and powder/propellant space. Please note that the Russian 20 X 99 and Japanese 20 X 94 use light (short) projectiles of 'standard' type. ONLY the Germans used the thin wall mine shell. The process of manufacturing the mine shell, while the concept is not difficult the actual execution is, was notable enough that the company's trademark symbol is a reference to the process. It is a similar process to making brass cartridge cases. Doing it in steel is a lot more difficult. Also please note that most cases taper, this aids extraction. Totally straight cases can cause problems and the higher the pressure the more problems. The Blow back guns usually operated at lower pressures than the locked breech guns.


Using short/light projectiles would probably be more practical than resorting to more extreme case modifications, and using short, wide projectiles tends to still allow proportionally more HE/I capacity than smaller, longer rounds. (though ballistic performance is worse due to shape and sectional density -I do wonder if using a shorter, lighter 30 mm round on the Mk 108 would have been a good compromise for improving muzzle velocity while retaining relatively high HE capacity, or perhaps the same to address the low velocity of the american 37 mm M4 -particularly as it was mixed with the high velocity .50 and .30-06 browning guns)

Aside from that, there's the existing larger .50 BMG derived ammunition types of the Hotchkiss 13.2 mm and Boys .55"/13.9 mm (actually .565 or 14.3 mm ) were of compatible case and nearly identical overall length to the .50 BMG round. Given these guns would be competing more with light 20 mm cannons than other machine guns, going with the later/heavier round would make more sense, and 14.3 mm is getting into the range where more useful HE capacities are possible even in conventional shells. (not to mention high incendiary capacity and potential for self-destruct explosive/incendiary rounds)

In the British case (and possibly Italian or others looking for a lighter HMG) adopting a lightened browning rechambered for the .5" Vickers round would still be attractive and fairly similar to ballistics of both the .303 and Boys. (at least the lighter, lower velocity loadings for the Boys -high velocity likely wouldn't be usable due to the structural limits in the existing M2 Browning anyway)

On the note of capacity though, it's notable that the pre-war 23 mm madsen round seems to have used some sort of shell design allowing relatively high capacity. I'm not sure of the construction methods, but it appears thin walled at least and the 23.65 mm projectile could carry nearly double the HE charge of the 20 mm Madsen round. Additionally, the 23 mm gun was belt fed and had a slightly higher rate of fire (360 RPM) while being lighter than the early Hispano and having a reasonably high 720 m/s muzzle velocity. Seems like it'd be attractive for licensed production, unless Madsen was solely offering it as export in which case it still seems attractive for the Germans to use after Denmark was captured. (seems like a good choice for the 109's nose gun)

It certainly seems like a better choice than the 37 mm M4 on the P-39, possibly better than the American Hispano as well and probably useful for some roles on British fighters as well. (closer ballistics to the .303, lighter than the earl hispano, already using belt feed and a very good anti-bomber weapon,though perhaps rechambering the Hispano for the Madsen round -or necking out the Hispano case to fit the Madsen shells would be a preferable successor if further development of the Madsen gun itself was unattractive)


Edit: forgot to link references for the Madsen


DziaÅ‚ko lotnicze 23 mm Maskinkanon (Madsen) Â» Encyklopedia Uzbrojenia II Wojny Åšwiatowej

And cut-away pictures of the shell
http://milpas.cc/rifles/ZFiles/Misc/Cartridge Collection/sectCannon.jpg

from:
PHOTO GALLERY


Here's some good ones showing the .50 Browning and .55 Boys side by side

http://milpas.cc/rifles/ZFiles/Misc/Cartridge Collection/sectHMG.jpg

And not quite as nice showing of the .50 and 13.2 mm Hotchkiss cartridge next to the Soviet 12.7x108 and Vickers 12.7x120 
http://milpas.cc/rifles/ZFiles/Misc/Cartridge Collection/HMG1.jpg


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## kool kitty89 (May 4, 2015)

tomo pauk said:


> Granted, the Ho-5 wasn't that a powerful (79g shell at 750 m/s), but I don't think it was under-loaded. Please check out the quote in post #5 here.
> For the 18mm, I agree that it should be around 700 m/s for the 100g shell, though I'd rather have an 80 g at 750+ m/s.


The WWII Fighter Gun Debate: Gun Tables
_The Ho-5 was lighter, had a high rate of fire, and it was belt-fed instead of drum-fed. But near the end of the war the Japanese had a shortage of high-strength alloys, and to compensate for the reduced strength of the guns the Army reduced the pressures. Hence the muzzle velocity of the Ho-5 dropped from 820 m/s to 700 - 730 m/s._

That seems to imply intentionally limiting propellant loads, that combined with the somewhat higher capacity cartridge than the German 20x82 mm and lower velocity with lighter shells seems to imply propellant loads well below the limits of the cartridge itself. (granted, plenty of gun use cartridges with loadings less than their potential maximum, including the .50 BMG itself)



> My idea was to either push the base .50 cartridge up to the biggest size of the shell that is practically possible, or to come out with a belt fed 20 mm cannon that is lighter than MG 151/20, let alone Hispano. The 17-18mm exploding ammo was well within the scope of any major armament/ammo producer in the world, even in late 1930s.


Modifying the case base or overall length to a significant degree would mean more comprehensive changes to the gun itself, not impractical but not as simple and a barrel change, so more like the scaled-up Ho-5 itself. (or scaled-down Ho-103)

You're basically aiming at something slightly heavier than the Oerlikon FFL (and still somewhat lighter than the FFS), while being belt fed, able to be synchronized and having a significantly higher rate of fire (unsynched) at roughly similar velocity but firing a smaller, lighter projectile still in the small 'cannon' class around .7" caliber. 

That said, using the existing .50 BMG cartridge and simply necking it out even further than the .55" Boys did, keeping the projectile relatively short to maintain total length would probably result in something with the overall weight and performance characteristics you're looking for anyway, or at least something more attractive than the FFF in ballistic performance and better than the FFF and FFL in terms of rate of fire, belt feed, and synchronization potential. (and significantly lighter than the FFS) Dropping closer to 15 mm would probably beat the FFL in ballistics/velocity as well. (the 14.3 mm diameter '.55" Boys' round managed better than the FFL ... better than the Hispano for some high velocity AP cartridges, but I'm not sure those would play nice with the existing M2 -decent indication of potential loadings for heavier shells though, at least ones short enough to maintain the existing 12.7x99mm case capacity)



> Bolded part is one of main benefits of the BMG - it was belt fed from the get go. The significantly lighter weight is another (both for gun and for ammo), and should remain so even when modified for a bit more heavier projectile.


Yep, the only other belt-fed aircraft cannon available in the 1930s was the 23 mm madsen, and that was in the Hispano's weight/recoil class (or a bit lower), but had a fairly low rate of fire. Nice destructive power though, and possibly the best pre-war anti-bomber weapon. (and if further development for speeding up RoF was possible, it could have stayed competitive throughout the war as well -or, of course, engineering a browning derivative rechambered for the 23 mm madsen cartridge)





Shortround6 said:


> This could very well be why most HE ammunition for aircraft cannon was HE-tracer. Many designs used a passage way from the tracer compartment to the HE compartment with some sort of delay component to act as a self destruct mechanism. As the tracer burnt out it ignited the delay element which then burned into the HE compartment to detonate the shell.


Indeed, the 23 mm HE/T round (the one sectioned in Tony William's collection linked above) functioned that way, as did the 37x145mmR M54 HE/T shell used in the M4 autocannon.


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## Koopernic (May 4, 2015)

Shortround6 said:


> snip
> 
> The wing gun question gets rather interesting. The 20mm MG FF cannon weighed 28kg (bare gun) vs 17kg for
> 
> ...



The soviets seem to have gone for a heavy machine gun in their tanks; most times one sees newsreel footage of a T54 or T62 there is someone hand cranking the HMG. These tanks tended to go for a two man turret.

If the myths are to beloved these guns brought down multi million dollar F-111 along with AK47.

I've never quite understood why the ME 109F/G gave up on wing stations, it was a mistake as attempts to restore the ability in the ME 109K6 show. Even with MG131 they would have added significant fire power.

For the Germans I'm surprised the adoption of the 20mm power driven turret used on some Fw 200, JU 290 and Ju 352 as well as several sea planes didn't make it onto their armour. If the traverse and power mechanism was suitably recessed so that the expensive drive mechanism wasn't exposed it might have significantly boosted the defensible ability of armour. Perhaps the philosophy was just to take cover given the inaccuracy of weapons big enough to hurt a tank.


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## Edgar Brooks (May 4, 2015)

Once again, you're allowing yourselves to get blinded by all sorts of technical wizardry, while forgetting (or ignoring) what the Air Ministry actually wanted. 
If a round, from the main armament, couldn't penetrate German bombers' armour, they weren't interested, hence the concentration (from before the war) on the Hispano. Early Hispanos had drum magazines because of difficulty finding a working belt feed, not due to any fault in the design of the cannon; the first four-cannon-armed Hurricane II had Chattelerault belt-feed, with 100 rounds per gun, in mid-1940.
You can talk about machine gun round type, size, and weight as much as you like, but what interested the Air Ministry, in the Browning, was its rate of fire; if you couldn't throw out 1000 r.p.m., in 1940, forget it, they were not interested. Throwing that lot of lead at a German bomber (always considered the prime targets,) in their view, gave them at least a chance of disabling/killing the crew. The .303" was not replaced by the .5" until the RAF got the gyro gunsight, which meant pilots were likely to hit what they aimed at, so rate of fire was less important.


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## kool kitty89 (May 4, 2015)

Koopernic said:


> I've never quite understood why the ME 109F/G gave up on wing stations, it was a mistake as attempts to restore the ability in the ME 109K6 show. Even with MG131 they would have added significant fire power.


Before the MG-131 was available, even going back to wing-mounted MG-17s would be better than nothing (and wouldn't compromise the streamlining as the MG-FFs had -complying with the 109F's design philosophy), particularly given the early Fw 190s were still mounting 4 MG-17s along with the pair of MG-FF/Ms. That said, it seems like the MG-FF/M (particularly with 90 round drum) would have had advantages over the MG-151/15 used on early 109Fs as well. (more so if they'd compromised to retain the MG-FF wing mounts, 3x MG-FF/Ms would make a lot of sense and be a bit easier than the mixed trajectories, heavier recoil -and added weight- of MG-151/20s; deleting the cowl guns could save a little weight/drag too)



> For the Germans I'm surprised the adoption of the 20mm power driven turret used on some Fw 200, JU 290 and Ju 352 as well as several sea planes didn't make it onto their armour. If the traverse and power mechanism was suitably recessed so that the expensive drive mechanism wasn't exposed it might have significantly boosted the defensible ability of armour. Perhaps the philosophy was just to take cover given the inaccuracy of weapons big enough to hurt a tank.


Wouldn't such turrets at least be useful adapted to anti-aircraft tanks or were the existing cannon mounts on those types effective enough? 

Besides that, of the 20, 37, and 40 mm AA guns used on, it seems there might have been room for 30 mm too. I know there was a very late war attempt with the Kugelblitz and MK-103, but it seems like they could have tried something like that much sooner using the older MK-101. (twin mount MK-101s would be interesting compared to the Wirbelwind's quad 20 mm Flakvierling 38 while still being more compact and much faster firing than the single 37 mm flak -and belt fed, let alone the larger Bofors gun used on Hugarian tanks)






Edgar Brooks said:


> Once again, you're allowing yourselves to get blinded by all sorts of technical wizardry, while forgetting (or ignoring) what the Air Ministry actually wanted.
> If a round, from the main armament, couldn't penetrate German bombers' armour, they weren't interested, hence the concentration (from before the war) on the Hispano. Early Hispanos had drum magazines because of difficulty finding a working belt feed, not due to any fault in the design of the cannon; the first four-cannon-armed Hurricane II had Chattelerault belt-feed, with 100 rounds per gun, in mid-1940.


In that case, wouldn't a high velocity heavy machine gun or light cannon be attractive as well? Ignoring HE/I carrying potential entirely and purely looking at AP, there's a lot you can do with smaller weapons than the hispano, especially for aircraft armor and especially looking at anti-tank rifle rounds in the 13-15 mm range, including high velocity AP rounds of the .50 BMG cartridge itself. (armor penetration is certainly a reason to ignore the Oerlikon FFF and .5 Vickers round ... somewhat less so the FFL) 

Something closer to the MG-151 would seem ideal for air to air armor penetration within the limits of small late-30s fighter aircraft, so why not concentrate on something more like that? (or even consider necking the Oerlikon FFF DOWN to something like 15 mm or even the .55" Boys projectile)


Aside from that there's still the Madsen cannon. Slower firing than the Hispano, but lighter and belt-fed.


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## Edgar Brooks (May 4, 2015)

kool kitty89 said:


> In that case, wouldn't a high velocity heavy machine gun or light cannon be attractive as well? Ignoring HE/I carrying potential entirely and purely looking at AP,.


Which you can't do, because the Air Ministry wanted armour-piercing and explosive in the same round.


> Something closer to the MG-151 would seem ideal for air to air armor penetration within the limits of small late-30s fighter aircraft, so why not concentrate on something more like that? (or even consider necking the Oerlikon FFF DOWN to something like 15 mm or even the .55" Boys projectile)


Because they were able to get a licence agreement with the owners of the Hispano to build it here, in specially built factories, ensuring that there would be no interruption of supply.


> Aside from that there's still the Madsen cannon. Slower firing than the Hispano, but lighter and belt-fed


And, with "slower firing" you've immediately blown it, since the consideration had to be on getting as much hitting power in one or two seconds as possible. How many aircraft were fitted with the Madsen, incidentally? The Ministry files never mention it.


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## Shortround6 (May 4, 2015)

Edgar Brooks has a point. 

It is also a true that the 'Air Ministry' tried to use technical wizardry (pretty low tech to be sure) to compensate for for poor training and less than ideal gun sights. Pointing many guns in different directions to compensate for poor aim is hardly compatible with fewer guns that are more effective on an individual basis. 

However we also have to consider that the British barely had enough .303 Brownings to go around. Or perhaps they didn't have _all_ that they wanted and used substitutes to some extent. In 1940 they certainly didn't have enough of the better types of .303 ammo that they wanted. Given that little fact, trying to make hundreds of thousands of little shells with fiddly little fuses seems a complication they didn't need at the time. During the BoB many eight gun fighters were flying with only one gun loaded with De Wilde ammunition. It had only gone into mass production in the spring of 1940. Scaling it up to suit various 11-18mm schemes in 1935-39 would have needed a time machine. Only two guns were loaded with MK IV incendiary/tracer which dates from WW I. Two guns were loaded with AP. Using infantry style lead filled (with soft nose filler) ammo in 3 guns certainly points to some sort of ammo shortage. By the middle of the war the four .303s left in Spitfires were firing two guns with AP and two guns with De Wilde. The De wilde was rated as twice as effective as the old incendiary/tracer at setting fuel tanks on fire. 

It took time to sort out the fuses even on 20mm ammo, early Hispano fuses acted too quickly and exploded on the skin of the aircraft which limited the structural damage and damage to components and items further inside the plane. This was enough of a problem that inert training ammo with steel caps were issued as a "ball" round, no explosion but the kinetic energy was formidable. 

Tanks a have a big problem. Unless designed/commanded by Dr. Who they are almost always volume limited and fitting such things as power AA turrets to 'standard' tanks took up too much space and took away from the tanks primary purpose. 

If you are going to dedicate a chassis to AA use then the aircraft turrets mounted too few guns and guns without enough power for what was wanted. 

Rolls Royce did design a MG that in one version use the .55 cal Boys round. However it took them too long (they seem to have been distracted by other things  and by the time it was ready it was a. not really wanted and b. they were being told to concentrate on designing and building better engines.


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## Shortround6 (May 4, 2015)

I would note that in the thinking of the time, it was thought that 2-3 seconds was all the firing time a pilot would have on one firing pass so the Hispano offered at least two and possibly 3 firing passes even with the drums. 
It also took a lot longer to sort out the belt feeds than originally thought. They changed from pulling on the rims to get the rounds out of the belt to pushing on the noses (not really a good idea with nose fused HE ammunition) to pulling on the rims again. 

The 20mm Hispano lasted 14 years in British service before _starting_ to be replaced by the 30mm Aden cannon so it could hardly be said to be a bad bargain or investment. Adopting some sort of interim gun in 1937-38 would have just meant adopting the Hispano at a later date and a waste of money and time.


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## Greyman (May 4, 2015)

Shortround6 said:


> Pointing many guns in different directions to compensate for poor aim is hardly compatible with fewer guns that are more effective on an individual basis.



Interestingly enough the British eventually found this very scenario to be the case.

Firing at a target 250+ yards away, the vast majority of the time the failure to destroy the target wasn't due to lack of bullet concentration - but errors in aim. With only two main weapons (20-mm Hispano), it made sense to spread the guns so that they covered a larger area at 250 yards. Most kills were made from under 150 yards and the slight spread made almost no difference at these ranges.



Shortround6 said:


> However we also have to consider that the British barely had enough .303 Brownings to go around. Or perhaps they didn't have _all_ that they wanted and used substitutes to some extent. In 1940 they certainly didn't have enough of the better types of .303 ammo that they wanted. Given that little fact, trying to make hundreds of thousands of little shells with fiddly little fuses seems a complication they didn't need at the time. During the BoB many eight gun fighters were flying with only one gun loaded with De Wilde ammunition. It had only gone into mass production in the spring of 1940. Scaling it up to suit various 11-18mm schemes in 1935-39 would have needed a time machine. Only two guns were loaded with MK IV incendiary/tracer which dates from WW I. Two guns were loaded with AP. Using infantry style lead filled (with soft nose filler) ammo in 3 guns certainly points to some sort of ammo shortage. By the middle of the war the four .303s left in Spitfires were firing two guns with AP and two guns with De Wilde. The De wilde was rated as twice as effective as the old incendiary/tracer at setting fuel tanks on fire.



I'm not aware of any large issue with .303 Browning production - and I can't see earlier in the thread what you are referring to when you mention substitutes for the Browning ... skimmed around but I'm missing it ...

As for ammunition - I can't cite any specific tests, but from documents on discussions/correspondence within the RAF it seems that the large use of .303 ball rounds early in the war was due to the belief that .303 AP rounds were more easily deflected from aircraft skin/structure coupled with general lack of armour on enemy aircraft at the beginning of the war.


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## Shortround6 (May 4, 2015)

The shortage of Brownings rarely applied to fighter guns (at least once the shooting started, a few Spitfires were initially delivered with only 4 guns and were fitted with the full eight when already issued to service squadron/s, a few early Gladiators were fitted with Lewis guns under the wing until they could be replaced by Brownings) or fixed forward firing guns, but Some planes (like Blenheims and Hampdens) may have soldiered on a bit too long with Vickers K guns for rear defense instead of Brownings. Likewise Wellington waist guns. The Vickers K gun did OK but it could have been replaced by the Browning in many cases if more Brownings had been available. Some planes got Lewis guns in 1937-38 because there weren't enough Vickers K guns to go around. Early Blenheims had a single Lewis gun in the turret (which only traversed 180 degrees). The British did manage to keep things moving along and few, if any planes had to fly without some sort of gun in a position where there was supposed to be one but the British didn't have any surplus of .303 Brownings. Futzing about with oddball alternatives wasn't going to improve things.


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## Greyman (May 4, 2015)

I don't think the use of the Vickers K was due to any lack of Brownings - more of a pre-war choice by the RAF that ended up being too simple and not effective enough for reality.

The delay in getting Brownings into aircraft when the British realized the Vickers K's lack of effectiveness was more due to the development time of the mounts and feed mechanisms than any supply problems with the weapons themselves.


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## fastmongrel (May 5, 2015)

One of the good points about the Vickers K was it was so quick and simple to fit to an aircraft. All you need is a hole in the fuselage a bracket to mount the gun and somewhere to store the drums of ammo. Fitting belt fed guns is less simple you need a system to feed the belt so it doesnt snag as you traverse or ammunition rails as the rear turrets used.


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## Shortround6 (May 5, 2015)

You can fit belt fed guns using 100-200 round ammo boxes attached to the gun and mount. Not as big as an advantage as having 400-2500 rounds available without having to change belts/boxes but it could be done. Squadron only needs armorers trained on one gun and only one set of spare parts. (something else to think about when coming up with suggestions for different guns than used historically).

Many countries _could_ have used Brownings or Browning derived guns to advantage _given unlimited factory space/capability_. British could have found a .5in Browning (Japanese Ho-103) rather useful as a _defensive_ weapon as the Hispano didn't fit well in turrets. However the change would NOT have allowed the 4 engine heavies to operate any better by day and would not have changed the overall strategy or tactics of the airwar. 

Italians could have used them but then we are back to factory space. Italians would have had to tool up before WW II.


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## Greyman (May 5, 2015)

Shortround6 said:


> However the change would NOT have allowed the 4 engine heavies to operate any better by day ...



Harris disagreed and was pretty pissed that he was unable to get the .5-in Brownings he wanted in his bombers.


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## Greyman (May 5, 2015)

I don't think the British were interested in 100-200 round boxes. You're in just as bad or worse of a position than with the Vickers K - once you factor in trying to reload.

EDIT: In fact I found an A&AEE paper on the very Browning arrangement you picture in image #3:
_The defense provided by the upper guns is extremely poor. The field of fire, in flight is very restricted and the limitation of belt-fed guns to 100-round magazines is a most undesirable limitation of the armament provided. It is considered that the twin Vickers G.O. mounting tested by this Establishment in Havoc BJ474 is far superior in every way to the Bell Adapter fitted in the Boston III.
_
I have documents on the efforts to beef up the armament on many British planes, and in all of the wires/letters back and forth between and amongst the ministries/firms involved the supply of Brownings is never the issue.


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## Shortround6 (May 5, 2015)

Harris may have disagreed but if B-17s and B-24s couldn't operate in daylight with 10-13 .50 cal guns each and flying at over 20,000ft the _actual_ chances of Halifaxes or Lancasters with 8-10 .50 cal guns and flying lower seem pretty slim. 
This is with the benefit of hindsight. What people thought in 1943 was different. .50 cal guns in British bombers _may_ have been better for shooting at nightfighters, I don't know.


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## Greyman (May 5, 2015)

Shortround6 said:


> Harris may have disagreed but if B-17s and B-24s couldn't operate in daylight with 10-13 .50 cal guns each and flying at over 20,000ft the _actual_ chances of Halifaxes or Lancasters with 8-10 .50 cal guns and flying lower seem pretty slim.
> This is with the benefit of hindsight. What people thought in 1943 was different. .50 cal guns in British bombers _may_ have been better for shooting at nightfighters, I don't know.



He definitely wasn't planning to get .5-in Brownings into his bombers and have them operating in long-range, unescorted, daylight missions. But there were many cases where his aircraft did operate in daylight and he wanted them to have the heavier armament.


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## Shortround6 (May 5, 2015)

Greyman said:


> I don't think the British were interested in 100-200 round boxes. You're in just as bad or worse of a position than with the Vickers K - once you factor in trying to reload.
> 
> I have documents on the efforts to beef up the armament on many British planes, and in all of the wires/letters back and forth between and amongst the ministries/firms involved the supply of Brownings is never the issue.



Thank you, I may be corrected, however what are the dates of the documents? The .303 Browning shortages that I am referring to are mostly (or entirely) pre-war. The time of the _introduction_ of the first Spitfires, the first Gladiators, Blenheim Is and such. By the Fall of 1939 and later the production may have been increased enough to cover the majority of needs, especially with the K gun covering the minor uses so shortages were no longer an issue. I know that at least two British companies built .303 Brownings and there may have been more (or sub contracting) and/or purchases from over seas? Some of the early Blenheims and Battles got Lewis guns because the K gun was not in production yet. 

What is being proposed here is introducing a 4th gun ( Browning .303, Vickers K gun, Hispano, +?) into the "mix" or replacing the Hispano and doing it in the 1937-39 time frame.From a manufacturing point of view, if England is just barely making enough Brownings in 1937-39 ( regardless of what they did later) then trying to introduce a "new" gun is only going to cause delays in the guns that were made.


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## Shortround6 (May 5, 2015)

Greyman said:


> He definitely wasn't planning to get .5-in Brownings into his bombers and have them operating in long-range, unescorted, daylight missions. But there were many cases where his aircraft did operate in daylight and he wanted them to have the heavier armament.



But then it doesn't really change much in the outcome of the war does it? A few lower losses on a few specialized missions? Important to the crews that took part. Perhaps important to Harris in building bomber command or the perception of bomber command ("look at what _Bomber Command_ can do, all you politician that allocate money") but not important to the overall outcome of the war. Are twin .50 tail and top turrets in place of quad .303 turrets really going to change the loss rates that much?


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## Timppa (May 5, 2015)

Commander of the Fighter Squadron 24 , G.Magnusson wrote a memo after the Winter War, Spring
1940:
"With 4 .30 Browning machine guns with ball rounds it was difficult to shoot down enemy bombers. 
Later, with incendiary and AP bullets, the SB's and DB's could be flamed with 200-300 rounds.
These results were improved when all four machine guns were converged to 150 metres.

This armament was satisfactory against bombers, but against fighters it was too weak due to bullets deflecting from the strong seat armor.

To operate succesfully in the future we should definitely switch to heavier calibre machine guns 
or, if possible, to 20-23mm hub cannon. This armament would be effective, regardless of the enemy planes are faster or slower than ours."


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## Greyman (May 5, 2015)

Shortround6 said:


> Are twin .50 tail and top turrets in place of quad .303 turrets really going to change the loss rates that much?



Probably not, but who knows? It's not just applying the upgraded armament to what Bomber Command did - but also thinking of all the instances of what they would have done differently had they had the armament.

For example, there was one colossal Anglo-American daylight mission to Berlin planned when the Germans were in full retreat in the West in a hope to panic the German Government at a critical moment. Harris:
_
'General Doolittle came up to Bomber Command on the afternoon before the projected attack and he and I and our staffs examined the final plan together in the Operation Room. The routes were pretty well cut and dried and when I discovered that the Americans, whose long-range fighters were required to protect Bomber Command's striking force as well as their own Fortresses, were unable to raise enough fighters to give what I considered adequate cover for our aircraft during such a deep penetration of Germany. 

... 

There had been some misunderstanding about this in the earlier stages of planning the operation, since it was only on the day before the operation was to take place that I discovered that an American long-range fighter force was insufficient to cover both out own and the American bombers all the way to Berlin was not available.

Although Jimmy Doolittle did his utmost, as always, to meet our requirements I had to refuse to subject my force to a risk far greater then usual - I had particularly in mind our obsolete .303 calibre defensive armament - the whole operation was therefore cancelled.'_

Also, to characterize Bomber Command's daylight efforts as '_a few specialized missions_' is missing the mark by quite a bit.


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## Koopernic (May 5, 2015)

If the practices of German night fighter aces is to be believed the 303 was effective. If the night fighter was discovered by the bomber and subjected to fire the policy of an experienced pilot was to break of the attack and seek another quarry. It was better to live and to fight another day than to subject yourself aircraft and crew to such risk. The 303 was often observed to give accurate return fire out to 800 meters.

The nature of a night fighter attack is different of course, it's a much slower approach, and most bombers shot down apparently did not see the attack coming. However if seen, say in moonlight the 303 was adequate.

The use of 3cm blind fire radar radar in the rear turrets of allied bombers would have been a temporary advantage since ultimately a night fighter with a 75cm radar dish and 4-6 2.0cm canon is going to beat two 0.5 inch Brownings aimed by a 30cm dish. The progression of proposed gun stations for the Lancaster appears to have been the elimination of guns in the tail, with only the gunner seated there, now in a fixed position, with an enlarged radar dish. A pair of 20mm Hispano guns in a ventral and dorsal positions would then be used to provide a very credible fire power in terms of range and destructive capability.

German work on blind fire radar had gun back to the very inception of its Liechtenstein series of radars. These radars used horizontal and vertical lobe switching to indicate the direction of a detected target and gave a surprisingly accurate indication of whether the target was dead ahead and as the German Navy and the ground based guns were already using blind fire and lobe switching it was an obvious candidate. The systems carried names such as "Pauke SD" and would have been able to centre a target, for some reason it never came in to use. However the use of microwaves allowed compact dish antenna and the same techniques as AAA radar and all allied and German nigh fighter radar would have had this ability by end of 1945. The USN actually had it before then. The kinds of ranges and firing times now would benefit from a much longer ranged bigger gun.

The USA in its bombers such as the B47 and most early B52 continued to use the 0.5 probably appreciating its compactness in the rear gun station where it was important to have streamlining and room for as many sensors as possible. The appearance of the 20mm Gatling style mechanism seems to be what finally swung the US solidly into the 20mm camp where it has remained to this day.


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## yulzari (May 5, 2015)

Anecdotal evidence is, of course, not itself evidence but I do recall an ex Bomber Command Lancaster rear gunner telling me that he and his crew regretted the twin 0.5" turret introduction as they felt that the role of the gunner was to frighten a night fighter into breaking contact and x4 tracers looked far worse at night than x2. Hitting the night fighter was thought to be incidental and he used to arrange for his belts to be all tracer whatever the powers that be may have wanted.

On the .303" Browning shortage; surely every new weapon is in shortage when first introduced until production churns out enough to go around?

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## Greyman (May 5, 2015)

yulzari said:


> Anecdotal evidence is, of course, not itself evidence but I do recall an ex Bomber Command Lancaster rear gunner telling me that he and his crew regretted the twin 0.5" turret introduction as they felt that the role of the gunner was to frighten a night fighter into breaking contact and x4 tracers looked far worse at night than x2. Hitting the night fighter was thought to be incidental and he used to arrange for his belts to be all tracer whatever the powers that be may have wanted.



Yeah the tactics ran the full gambit, I'm sure. I read one anecdote where a bomber 'skipper' told his gunners that he would shoot them himself if they ever fired their guns - not wanting to give their position away whatsoever and survive solely through evasive action. The main fear being that night fighters could be operating somewhat in pairs and even as you were driving off one fighter another could be closing in using your tracer as a guide.


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## Edgar Brooks (May 5, 2015)

Shortround6 said:


> The .303 Browning shortages that I am referring to are mostly (or entirely) pre-war. The time of the _introduction_ of the first Spitfires, the first Gladiators, Blenheim Is and such..


I'd be interested to know the source of that information, since nobody, that I've spoken to, has ever heard of it, and there's no mention in any of the official files.
70 (only) Gladiators had Lewis, Vickers Mark III/V, or Vickers "K" guns (with Browning guns thereafter,) and all 70 were delivered in early 1937, long before the first service Spitfire was delivered to 19 Squadron in August 1938. Test aircraft had to be flown with a full complement of guns, and then delivered in the same way, or the CoG could be compromised. It also seems strange that the Hurricane apparently wasn't included in this drama.
The Rose turret was a direct result of Village Inn, a system of radar detection from the rear turret, plus infra-red recognition of following aircraft, plus the gyro gunsight. This also led to the removal of tracer, since the gunsight "aimed off" for the gunner, so that it was hoped the nightfighter pilot would never know what hit him.


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## Shortround6 (May 5, 2015)

Edgar Brooks said:


> I'd be interested to know the source of that information, since nobody, that I've spoken to, has ever heard of it, and there's no mention in any of the official files.
> 70 (only) Gladiators had Lewis, Vickers Mark III/V, or Vickers "K" guns (with Browning guns thereafter,) and all 70 were delivered in early 1937, long before the first service Spitfire was delivered to 19 Squadron in August 1938. Test aircraft had to be flown with a full complement of guns, and then delivered in the same way, or the CoG could be compromised. It also seems strange that the Hurricane apparently wasn't included in this drama.



Which is it? No "shortage" or 70 Gladiators fitted with Lewis and Vickers guns? 

The "story" _such as it is_, is on page 93 of "Flying guns of World War II". I say "such as it is" because some people seem to making more of it than it really deserves. BSA reached a production schedule of 600 guns per week in March 1939. They peaked at 16,390 for the month in March 1942. It is really so hard to believe that in 1937 or mid 1938 production of the Browning was not quite up to speed to equip ALL new aircraft? 

Fighter aircraft are often flown without guns, in some cases they need ballast to maintain the CG and in some cases they do not. Any Spitfires delivered without the full eight guns were soon fitted with them in the field and *well before* the war started. In some cases flight tests were done on unarmed planes carrying ballast to represent armament. 

The premise of this thread is what countries could have used the .50 cal Browning, or versions of it, starting in 1938/39. In England's case they were just getting the .303 Browning into service and production at that time and trying to get the Hispano started up. Useful as a 3rd gun _might_ have been (or not) it could only come at the cost of delays in the existing .303 Browning and Hispano programs and was not something the British could afford at that time.


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## Greyman (May 5, 2015)

Found another tidbit, for what it's worth:
By July 1939 the Air Ministry estimated that 15,000 to 20,000 Brownings had been issued to the Service.


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## kool kitty89 (May 6, 2015)

Edgar Brooks said:


> Which you can't do, because the Air Ministry wanted armour-piercing and explosive in the same round.


And the potential for explosive/incendiary in 13-15 mm rounds wouldn't cut it? Let alone cause a re-think of the cancelled Mk.V incendiary round of the .303. (too complex/costly to use a fuze on the smaller round, but -prior to the Mk.VI- may have been more attractive on a larger caliber projectile).

Aside from that, there's the primary argument of these sorts of threads hinging on the powers that be (UK or any other government in question here) thinking/making decisions differently. I for one tend to prefer to try to avoid hindsight outright for motivation, and focus on potential reasonable/rational incentives for choosing differently.

From a practical standpoint there's 3 major ways to destroy enemy aircraft: killing the pilot/crew (requiring armor penetration or selective angles of attack), igniting fuel tanks (requiring incendiary ammunition and/or explosive), or causing critical structural failure by hitting an ammunition magazine, major structural components or concentrated damage to load-bearing minor components, control surfaces/mechanics, hydraulics, or damage to engine, oil or coolant radiators, coolant/oil or fuel tanks substantial enough to cause rapid draining of fluid. Some of those may be armor protected as well, so aside from tearing holes big enough to circumvent sealing, there's the matter of armor penetration. Aluminum is also generally non-sparking, but aircraft with steel structural components could potentially act as ignition sources for AP ammunition, same for strikes to the engine resulting in fire.

Pilot/crew vulnerability is relatively limited even without armor, so ability to cause crippling damage ANYWHERE on the aircraft's structure is significant.



> Because they were able to get a licence agreement with the owners of the Hispano to build it here, in specially built factories, ensuring that there would be no interruption of supply.


Any that license was easier to obtain than the one for the .303 browning or Oerlikon? The British at very least were using import Oerlikon FFS cannons, if not having a domestic license (I'm unsure of the specifics), but that seemed a rather pointless gun to try as an alternative to the Hispano given the weight and recoil advantages were modest and rate of fire was much lower. (the FFF or FFL would have made much more sense, especially the latter if they wanted decent armor penetration as well -FFF might be more interesting in defensive arrangements, but standardized production of fewer distinct types would probably favor the FFL)

Aside from that, the browning adapted to a larger round (more so rechambered for a more powerful round, while the simpler barrel/ammunition change would make more sense for smaller militaries, but would still be a quicker adaptation) would be the other alternative and the one more relevant to this thread.

Either way limiting the number of new guns in production (and to lesser extent, being explored for acceptance into production) would be a concern as well. Considerations for replacements for the .303 in both fighter AND defensive armament positions would be a consideration as well, and effective ability to not only produce a gun but have it reliable and practical to install on existing aircraft (or those about to enter service) would also be significant. (the FFF and FFL, while not able to be synchronized, may still have been practical to fit underwing on the Gladiator, and certainly be much easier to adapt to the Spitfire and Hurricane -and any defensive mounting- than the Hispano)



> And, with "slower firing" you've immediately blown it, since the consideration had to be on getting as much hitting power in one or two seconds as possible. How many aircraft were fitted with the Madsen, incidentally? The Ministry files never mention it.


Given the 23 mm madsen packed about double the damage per round, the 'hitting power' would have been about the same, provided you're not firing on a rather light/weak aircraft. (in which case the .303 batteries would be preferable anyway)

The USAAC (and possibly USN) are the only air forces I'm familiar with seriously considering and testing the 23 mm Madsen. It was planned for use on the P-38, P-39, and tested in underwing fairings on the P-36. Plans to adopt it were canceled after the fall of Denmark as they seemed to be relying on import purchase rather than licensed production (or in any case, had failed to secure a license by that time). The much heavier, much slower firing 37 mm M4 cannon was then substituted on both the P-38 and P-39. (though both had already had the M4 slated as an alternative or competing weapon and the primary choice of Bell who'd previously used it on their Airacuda)

If nothing else, the Madsen ammunition should have been appealing and seriously considered for adapting the Hispano to. (rechambering it or necking out the 20x110 mm cartridge)

There may have been difficulties securing licenses from Madsen, and the US and UK hadn't adopted their 20 mm AA gun either. (still odd the Germans didn't get use out of the 23 mm madsen, or adapting the round to one of their own weapons)


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## kool kitty89 (May 6, 2015)

Shortround6 said:


> Edgar Brooks has a point.
> 
> It is also a true that the 'Air Ministry' tried to use technical wizardry (pretty low tech to be sure) to compensate for for poor training and less than ideal gun sights. Pointing many guns in different directions to compensate for poor aim is hardly compatible with fewer guns that are more effective on an individual basis.


That sort of logic may have also contributed to their very different feelings towards concentrated nose armaments, synchronized or otherwise, and the lack of hub cannon provisions on the Merlin. (that change alone would have made the Hispano seriously more useful and practical, especially as a high-precision weapon for pilots with exceptional aim)

Centerline armaments still allow the option to spread for pilots that understand the variety of tactics available. Provided they KNOW the aiming difficulties in play, applying a slight amount of cross controlling or rudder drift to spread the area of fire would be a practical option too. (not the same as the shotgun effect of huge wing batteries, but also more flexible in allowing the pilot some choice of when to use it, granted doing that on the vertical axis would be bad on early Merlin aircraft without compensation for negative-G)

Though that said, having a combination of wing AND nose armement allows both a compromise and better spread of fire. A 3 cannon armament would have been plenty useful and perhaps ease adoption and practical use of the Hispano a fair bit. (but that arrangement would be useful for the Oerlikon and Madsen guns as well -or Hispano rechambered for 23 mm)




> However we also have to consider that the British barely had enough .303 Brownings to go around. Or perhaps they didn't have _all_ that they wanted and used substitutes to some extent. In 1940 they certainly didn't have enough of the better types of .303 ammo that they wanted. Given that little fact, trying to make hundreds of thousands of little shells with fiddly little fuses seems a complication they didn't need at the time. During the BoB many eight gun fighters were flying with only one gun loaded with De Wilde ammunition. It had only gone into mass production in the spring of 1940. Scaling it up to suit various 11-18mm schemes in 1935-39 would have needed a time machine.


Part of this discussion is seriously considering the Browning mechanism in general (M1919 included) earlier on, but hardly limited to British service.

The Madsen and Oerlikon guns have a number of advantages over the Hispano, aside from the less attractive FFS. The FFL and FFF in nose or wing mountings and the Madsen in nose and (maybe) later adapted to stiffer wings, but probably not as practical pre-war. The FFF is really only attractive for cases where the moderate weight and recoil increase of the FFL is unattractive, both are far more practical to use on most aircraft of the late 1930s than the Hispano. (and weighing the cost/benefit of further developing the oerlikon guns for higher rate of fire vs scaling the Hispano down to a lower powered cartridge and lighter weight/recoil -though the British Mk.I and Mk.II Hispano's RoF advantage over the FFL was more modest at 600 vs 500 RPM vs the higher RoF for the earlier -heavier- French HS.404 at 700 RPM)



> It took time to sort out the fuses even on 20mm ammo, early Hispano fuses acted too quickly and exploded on the skin of the aircraft which limited the structural damage and damage to components and items further inside the plane. This was enough of a problem that inert training ammo with steel caps were issued as a "ball" round, no explosion but the kinetic energy was formidable.


A soft core cannon shell would indeed be more useful in leu of problematic HE ammunition, and the same goes for ball or AP ammo with incendiary tip. The mushroomand fragmentation effects of ball type soft ammo wouldn't tend to punch straight through softer components, but expand/fragment and do a good deal more damage. (albeit for the few steel tubing based frames, it might be less useful -against aluminum stressed skin construction it'd work better -hard/AP ammo might do more damage to something like the hurricane's fuselage ... plus incendiary ammo would be very effective at igniting any nitrocellulose doped fabric -flame retardant dopants would be another matter, but I think one of the hurricane and Gladiator's problems early war was highly flammable doped fabric along with wooden stringers being used)



> Rolls Royce did design a MG that in one version use the .55 cal Boys round. However it took them too long (they seem to have been distracted by other things  and by the time it was ready it was a. not really wanted and b. they were being told to concentrate on designing and building better engines.


If they didn't use the browning as the basis for the weapon, adapting the M2 Browning mechanism to that round would seem much more straightforward. (pushing it to higher pressures and velocities might be more of a problem, but adapting it to the larger projectile with the .55 Boys matching the cartridge dimensions of the .50 BMG already, it would be more a matter of limiting propellant load until structural reinforcements were completed -any mixed armaments still including the .303 would better match the lower velocity round anyway)

Aside from that, the .303 itself was retained in spite of its somewhat mediocre performance compared to 8 mm Mauser and .30-06 round due to volume production and substantial back inventory from what I understand, along with existing guns using it. Otherwise some modest improvement to even the light machine guns should have been possible by adopting different ammunition. (directly adopting the American M1919, ammunition and all would have given at least a modest boost to firepower due to the higher muzzle energy and slightly higher RoF)

The Air ministry made a fairly practical logistical decision in that regard, and I'd tend to agree with that one being reasonable on the whole a great deal more than the fixation on the Hispano. (particularly a wing-mounted hispano -or Oerlikon FFS)

Given the weight and overall performance I'd tend to think the Oerlikon FFF would be preferable to the Vickers .50 or Browning chambered for the same round, but the RoF and velocity of the latter might have been better. (depending how you view the drum armament of the FFF) The Vickers gun had jamming/reliability issues of its own, but perhaps less unreasonable in a defensive mounting where the mechanism can be reached and cycled/cleared. (plus it could have been adopted earlier than not only a hypothetical vickers-browning but earlier than the .303 browning was, at least historically)


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## kool kitty89 (May 6, 2015)

Shortround6 said:


> I would note that in the thinking of the time, it was thought that 2-3 seconds was all the firing time a pilot would have on one firing pass so the Hispano offered at least two and possibly 3 firing passes even with the drums.
> It also took a lot longer to sort out the belt feeds than originally thought. They changed from pulling on the rims to get the rounds out of the belt to pushing on the noses (not really a good idea with nose fused HE ammunition) to pulling on the rims again.
> 
> The 20mm Hispano lasted 14 years in British service before _starting_ to be replaced by the 30mm Aden cannon so it could hardly be said to be a bad bargain or investment. Adopting some sort of interim gun in 1937-38 would have just meant adopting the Hispano at a later date and a waste of money and time.


Would a developed Oerlikon FFL really not have been similarly useful? (with potential to be belt fed and reach at least 750 RPM at lower weight and recoil) Or a Hispano or Browning (or improved Madsen) derivative firing the very useful 23 mm madsen ammunition. (having closer merits to the post-war 30mm ammo)

Or, for that matter, switching to 30 mm outright before the end of the war using a browning, oerlikon, or hispano derivative. (the Japanese had some really nice 30 mm designs and the MK 108 was pretty close to what the British shifted to post war, if only it had shifted to a lighter round with higher velocity, the Japanese guns were closer to what the British ended up wanting, though)




Shortround6 said:


> The shortage of Brownings rarely applied to fighter guns (at least once the shooting started, a few Spitfires were initially delivered with only 4 guns and were fitted with the full eight when already issued to service squadron/s, a few early Gladiators were fitted with Lewis guns under the wing until they could be replaced by Brownings) or fixed forward firing guns, but Some planes (like Blenheims and Hampdens) may have soldiered on a bit too long with Vickers K guns for rear defense instead of Brownings. Likewise Wellington waist guns. The Vickers K gun did OK but it could have been replaced by the Browning in many cases if more Brownings had been available. Some planes got Lewis guns in 1937-38 because there weren't enough Vickers K guns to go around. Early Blenheims had a single Lewis gun in the turret (which only traversed 180 degrees). The British did manage to keep things moving along and few, if any planes had to fly without some sort of gun in a position where there was supposed to be one but the British didn't have any surplus of .303 Brownings. Futzing about with oddball alternatives wasn't going to improve things.


In the cases where drum/pan magazines were preferred, shortages of the Vickers K being replaced with the Lewis gun would make some sense, but in cases where belt feed was preferred and the browning was in short supply, wouldn't the Vicker's .303 gun make sense? (the jamming issues would be poor for wing mounts or cowl mounts with inaccessible breeches, but for flexible mounts it seems more reasonable -and the .50 vickers likewise) The .303 Vickers had a lower RoF than the Vickers K though, but higher than the Lewis gun and, again, we're talking situations where belt-feed is preferred.

And, again, where drum feed was prefered in flexible mounts, the Oerlikon guns should have been serious considerations. (either the FFF or FFL, the former in the same weight class as the .5 Vickers and more reliable, plus available earlier than any hypothetical .50 vickers-browning -the FFL would be more directly competitive with the .50 BMG itself or a 13.2 mm, and probably lighter than a .55 adaptation, plus the smooth recoil would allow for more stable aiming, especially for flexible mounts rather than powered turrets)







Greyman said:


> As for ammunition - I can't cite any specific tests, but from documents on discussions/correspondence within the RAF it seems that the large use of .303 ball rounds early in the war was due to the belief that .303 AP rounds were more easily deflected from aircraft skin/structure coupled with general lack of armour on enemy aircraft at the beginning of the war.


I'd think the AP rounds would have more an issue of punching straight through soft components without doing much damage, while ball rounds would tear larger holes in the skin and have greater likelihood of hitting control cables (or rods), hinges, hydraulic linkages, or potentially puncture fuel tanks. (and potentially tear larger holes in self-sealing tanks)





Shortround6 said:


> Many countries _could_ have used Brownings or Browning derived guns to advantage _given unlimited factory space/capability_. British could have found a .5in Browning (Japanese Ho-103) rather useful as a _defensive_ weapon as the Hispano didn't fit well in turrets. However the change would NOT have allowed the 4 engine heavies to operate any better by day and would not have changed the overall strategy or tactics of the airwar.
> 
> Italians could have used them but then we are back to factory space. Italians would have had to tool up before WW II.


Aside from potential browning derivatives, with the likes of the Madsen and Hispano rather heavy and powerful, it really seems like the Oerlikon FFF and FFL should have been the guns of choice for mid 1930s progression beyond LMG armaments, at least for un-synchronized configurations. The German MGFF modification might have been a bit better off if it'd retained the lighter projectiles of the FFF itself (rather than the lower velocity, heavier german round). The MG-FF itself ended up nearly as heavy as the FFL and significantly lower velocity.


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## Edgar Brooks (May 6, 2015)

Shortround6 said:


> Which is it? No "shortage" or 70 Gladiators fitted with Lewis and Vickers guns?


Don't split hairs; 70 in early 1937, followed by all the rest produced that year, plus all of those up to August 1938 (and the Spitfire's inception)plus all of the Hurricanes apparently having 100% fit of Brownings does not sit well with this story of shortages.


> The "story" such as it is, is on page 93 of "Flying guns of World War II". I say "such as it is" because some people seem to making more of it than it really deserves. BSA reached a production schedule of 600 guns per week in March 1939. They peaked at 16,390 for the month in March 1942. It is really so hard to believe that in 1937 or mid 1938 production of the Browning was not quite up to speed to equip ALL new aircraft?


It is when nobody, to my knowledge, has ever mentioned it, for example, in "British Aircraft Armament" R Wallace Clarke states only that 460,000 guns were manufactured in the U.K., plus spares for another 100,000, and doesn't even hint at any supposed shortages. 
Please remember that it was you who introduced the subject, so it's hardly surprising that those of us, ignorant of the story, want to know more.


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## Shortround6 (May 6, 2015)

Edgar Brooks said:


> It is when nobody, to my knowledge, has ever mentioned it, for example, in "British Aircraft Armament" R Wallace Clarke states only that 460,000 guns were manufactured in the U.K., plus spares for another 100,000, and doesn't even hint at any supposed shortages.



Talk about splitting hairs, BSA alone built the 460,000 guns with spares for another 100,000 but they didn't do it in 1937/38 did they? 

What part of "shortage in 1937/38" are you not getting? It certainly _doesn't_ mean a shortage for the rest of the war. There are often temporary shortages as production starts up of certain items which go away as production gets going. 

They built over 57,000 Hercules engines, doesn't mean in wasn't in short supply at times (Beaufighter IIs and Wellington IIs). 

There were shortages (temporary) of all sorts of things as the British (and most other nations) geared up in 1937-38-39. It doesn't mean the shortages lasted for entire war or even a large part of the war. 

One only has to look at the rear gun/s in the Blenheim to realize _something_ was going on. Starting with a single Lewis gun (hardly state of the art even in 1936 but better guns were not in production *yet*) it went to the Vickers K gun, then two Vickers K guns, A single Browning showed up somewhere and twin Brownings and finally a whole new turret with two widely spaced Brownings. Granted this took around 5 years. Whitleys got 4 Brownings in the tail but a single Vickers K gun in the forward turret. I can see how arguments could be made could be made using the Vickers gun on pedestal mounts, ring mounts, ball mounts or swing mounts. It gets a little harder to make the case in a turret where the ammo supply (or at least 200-600 rounds) can traverse with the gun/s.


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## Greyman (May 6, 2015)

Shortround6 said:


> One only has to look at the rear gun/s in the Blenheim to realize _something_ was going on. Starting with a single Lewis gun (hardly state of the art even in 1936 but better guns were not in production *yet*) it went to the Vickers K gun, then two Vickers K guns, A single Browning showed up somewhere and twin Brownings and finally a whole new turret with two widely spaced Brownings. Granted this took around 5 years. Whitleys got 4 Brownings in the tail but a single Vickers K gun in the forward turret. I can see how arguments could be made could be made using the Vickers gun on pedestal mounts, ring mounts, ball mounts or swing mounts. It gets a little harder to make the case in a turret where the ammo supply (or at least 200-600 rounds) can traverse with the gun/s.



Again, the pre-war use of Lewis/Vickers free guns had nothing to do with shortages of Brownings and all to do with choices made by the powers that be. The _continued_ use of inadequate defensive armament was due to the time it took to design, manufacture and distribute conversion sets for the additional armament.

In the case of the Lewis, the decision wasn't made to completely replace it with the Vickers until the latter had been in service for a year or so and its marked superiority was evident.

Ironically enough as I go through my material on all of this I do see numerous concerns for the supply of the Vickers GO gun - including Vickers having to cancel work on an aerodrome-defence gun in order to produce the required number of 'K' guns once the decision was made to 100% replace the Lewis.


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## Shortround6 (May 6, 2015)

kool kitty89 said:


> And the potential for explosive/incendiary in 13-15 mm rounds wouldn't cut it? Let alone cause a re-think of the cancelled Mk.V incendiary round of the .303. (too complex/costly to use a fuze on the smaller round, but -prior to the Mk.VI- may have been more attractive on a larger caliber projectile).



As a general rule of thumb the weight of the of the projectile varies with the cube of the caliber. This assumes similar construction, materials and shape. A 13mm projectile will be roughly 4 times heavier than a 8mm projectile and a 20 mm projectile will be 4 times heavier than a 13mm projectile or 16 times heavier than an 8mm projectile. _Simple_ theory gets thrown several curves (complications) in that the 8mm projectiles often have sizable components of lead in them while the larger ones do not. Steel having a rather lower density than lead. HE and pyrotechnical compounds have a much lower density than either. Wall thickness of the hollow projectile doesn't scale well. You need a certain minimum thickness for strength, both for centrifugal force (projectile spin) and to keep the pressure on the base of the projectile when firing from buckling the projectile in the barrel. This means, for practical purposes until the German mine shell, that projectile capacity did NOT change with the cube of the diameter but increased at a much faster rate. You don't need a much thicker shell wall on a 20mm projectile than you do on a 13-15mm projectile. 



> Any that license was easier to obtain than the one for the .303 browning or Oerlikon? The British at very least were using import Oerlikon FFS cannons, if not having a domestic license (I'm unsure of the specifics), but that seemed a rather pointless gun to try as an alternative to the Hispano given the weight and recoil advantages were modest and rate of fire was much lower. (the FFF or FFL would have made much more sense, especially the latter if they wanted decent armor penetration as well -FFF might be more interesting in defensive arrangements, but standardized production of fewer distinct types would probably favor the FFL)



a lot depends on timing, at certain times the Oerlikon guns required lubricated ammo (read greased or at least wax coated) which was frowned on for aircraft use. Grease/wax at 60 degrees F vs Grease/wax at _minus_ 30-40 degrees let alone 60 degrees below. What is tolerated aboard ship/s is not tolerated as much in aircraft or on land. Please remember that while war was looming they weren't shooting just yet and what was _desirable_ often held more importance than it did once the shooting started. Different countries may have had different standards of reliability. 
Please remember too, that in the case of Great Britain, they were not buying just for use in the British isles but for use through out the Empire. ANY gun or ammo had to tolerate a wide range of climatic conditions. 



> Aside from that, the browning adapted to a larger round (more so rechambered for a more powerful round, while the simpler barrel/ammunition change would make more sense for smaller militaries, but would still be a quicker adaptation) would be the other alternative and the one more relevant to this thread.
> 
> 
> 
> If nothing else, the Madsen ammunition should have been appealing and seriously considered for adapting the Hispano to. (rechambering it or necking out the 20x110 mm cartridge)



There is a lot of talk about re-chambering and necking out (or down). Some of these guns had a few MM to spare as far as overall cartridge length goes and some did not. The designation, such as 23 X 106 does not tell you the over all length of the round, it tells you how long the cartridge case is without projectile. It also does not tell you haw fat the case is (diameter of the body of the case). It _sometimes_ tells you how the gun was headspaced (how the cartridge is located in the chamber front to back) The 20mm Hispano case was 24.8mm in diameter and headspaced on the shoulder. This is what caused a lot of grief with the US guns. The US built guns had a chamber that was a bit too long and allowed the round to "float" a bit. If the chamber is too short the breech block cannot close all the way and the gun _should_ not fire. If too long the breech block will close and the firing pin will hit the primer, however if the cartridge is not held in a controlled manner, rim at the back or shoulder on case hitting shoulder on chamber, the case can move forward when hit by the firing pin with the effect of a light strike and a dud round bringing firing to a halt until the round can be ejected from the gun and a new one chambered. 
The Russian 23 X 115 round was 27mm in diameter through the body and the Madsen round was 29mm through the body. The Russian 20 ShVAK round was only 21.8mm though the body but had a 25.2mm rim on the back. 

Some guns worked a bit different and used a massive extractor (and spring) engaging the rim of the case to hold it against the bolt face. Some breech blocks were locked against the barrel at the moment of firing pin strike and some were not (blow backs) and some guns were set up so that there was a bit of delay between the cartridge firing and extraction starting, (chamber pressure dropped some before case started to move rearward) the blow backs depended on inertia and spring tension for the delay. Some guns used bolt accelerators, once the bolt/breechblock had moved a small distance and broken the case loose from the chamber walls it accelerated to a higher speed for the rest of it's travel. 

The taper on the .50 cal Browning case is there for a reason, so is the shoulder. They can be changed but eliminating them or reducing them to mere vestiges of what they were is going to play havoc with the guns ability to function without some _major_ development time.


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## tomo pauk (May 6, 2015)

kool kitty89 said:


> ...
> Aside from potential browning derivatives, with the likes of the Madsen and Hispano rather heavy and powerful, it really seems like the Oerlikon FFF and FFL should have been the guns of choice for mid 1930s progression beyond LMG armaments, at least for un-synchronized configurations. The German MGFF modification might have been a bit better off if it'd retained the lighter projectiles of the FFF itself (rather than the lower velocity, heavier german round). The MG-FF itself ended up nearly as heavy as the FFL and significantly lower velocity.



Looks like the Oerlikon FFF fired a 128 g shell at 600 m/s, the Ikaria MG FF fired the 134 g shell at same speed? The muzzle energy was 23-24 kj. For a 100 g projectile, that would be close to 700 m/s? The MG FFM used a bit smaller propellant charge, the 92 g shell went out at 700 m/s.
The MG FF didn't ended nearly as heavy as the FFL, but FFL received more development that gradually decreased it's weight from 43 to 34 kg, later to 30 kg. The development of the FFF/MG FF wasn't much pressed on, the only modification being the MG FFM, so the lower recoil could still operate the gun action. The FFL would be as easy/hard to install on the turets as MG 151 or Hispano V?

Since there is a violent opposition for the UK adoption of the 'big bang' Browning (  ), any opinion on how well would it served in LW or USAF/USN?


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## Edgar Brooks (May 6, 2015)

Shortround6 said:


> What part of "shortage in 1937/38" are you not getting?


The "38" part (and there's no need to be rude); Gladiators built in early 1937 had other guns fitted, while Gladiators built in mid/late 1937 and the whole of 1938 had Brownings fitted, as did all Hurricanes, and the first Spitfires in August that year. However much I try, I cannot equate that with this supposed shortage in 37/38; 37, yes, but 38, not a chance.


> It certainly doesn't mean a shortage for the rest of the war


Who mentioned the rest of the war? I certainly didn't, but simply pointed out that another (British) book, on armaments, makes no mention, whatsoever, of *any* shortage of Brownings *at any time*.


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## Jabberwocky (May 7, 2015)

Shortround6 said:


> The Gun was made by FN in Belgium Pre-war and they may have gotten a higher rate of fire out of it. Considering the trouble the Americans had getting it to 1200rpm any claims of prewar FN guns firing that fast _in service_ must be viewed with suspicion.



The FN-Browning was variously advertised at rates of 1000 rpm, 1050 rpm, 1100 rpm and 1200 rpm throughout the 1930s, so I wouldn't view the rate with too much suspicion. The most common figure I’ve come across is the pre-war literature is 1050 rpm, which is the rate the RAF got when they tested the gun in 1938. 

I would consider 1200 rpm to probably be the upper end of the cyclic limit for the gun. A maximum value, rather than an average value. 

The Finns also put a locally built version of the M2 Browning on their Brewster Buffalos and the VL Myrsky. The gun is recorded in Finnish sources as firing at 1000-1100 rpm, further lending credence to the notion that the Browning was capable of being uprated to more than 1000 rpm.

I think the Romanians put the FN-Browning on their IAR 80/81 as well. Dropped it from the design due to lack of guns, if I recall correctly.


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## Shortround6 (May 7, 2015)

Perhaps the FN factory and customers had different standards than the US ordnance dept? It took the US until mid-late 1944 to get the big Browning up to 1200rpm _with acceptable numbers of jams, parts breakage and gun/barrel life._ If you accept a higher number of jams and lower number of rounds between parts failures you may be able to get the higher rate of fire without too much trouble.


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## Vincenzo (May 7, 2015)

or could have higher standard in the production


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## Shortround6 (May 7, 2015)

The US had at least three different companies working on the high rate of fire .50 cal gun and each company went through multiple prototypes/versions. It took about 3 years from start of work to to get an acceptable model (the US Standards) and the version chosen had next to NO INTERCHANGEABLE PARTS with the M2 gun. It wasn't simply a lighten bolt and different spring. The High rate of fire guns had to be manufactured as such and no conversion kit to bring older guns "up to speed" was ever issued. 

Some of the American prototypes were much more successful than others and it wasn't a steady progression in rates of fire, some prototypes may have simply shown them _what not to do._ 
The US had decided it wanted 1 breakage and 5 malfunctions per 5,000 rounds fired at 1200rpm which may have been setting the bar a bit too high. The Russian 12.7mm machineguns were not designed to last for 5,000rounds without hte whole gun be replaced. 
see: page 4 and on. 
http://photos.imageevent.com/badgerdog/generalstorage/georgemchinnthemachinegun/TheMGV3a.pdf

The American .50 was also a barrel burner. Long bursts could take out some of the rifling. Even the 800rpm guns were _supposed_ to be limited to initial 75 round bursts and then shorter bursts. And I believe this was with chrome lined barrels. 

A bigger bore will help with barrel life.

Edit> The malfunction/breakage rates may be for the gun/s on a test range. Relatively clean and moderate temperature. Throw in widely varying temperatures, some dust/dirt/grit and trying to fire while turning ( 3-5 Gs holding ammo belts into the bottom of the ammo trays/boxes and rates of fire and malfunction can vary considerably. The Pre-war American .50s didn't meet their 'advertised' rates of fire either. Too much testing had been done with short belts and long belts, especially under "G" loads slowed the guns down if not causing malfunctions. As noted in the link, at some point even the pre-1200rpm guns were modified to roughly double their belt pull/lift capacity.


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## kool kitty89 (May 7, 2015)

Shortround6 said:


> As a general rule of thumb the weight of the of the projectile varies with the cube of the caliber. This assumes similar construction, materials and shape. A 13mm projectile will be roughly 4 times heavier than a 8mm projectile and a 20 mm projectile will be 4 times heavier than a 13mm projectile or 16 times heavier than an 8mm projectile. _Simple_ theory gets thrown several curves (complications) in that the 8mm projectiles often have sizable components of lead in them while the larger ones do not. Steel having a rather lower density than lead. HE and pyrotechnical compounds have a much lower density than either. Wall thickness of the hollow projectile doesn't scale well. You need a certain minimum thickness for strength, both for centrifugal force (projectile spin) and to keep the pressure on the base of the projectile when firing from buckling the projectile in the barrel. This means, for practical purposes until the German mine shell, that projectile capacity did NOT change with the cube of the diameter but increased at a much faster rate. You don't need a much thicker shell wall on a 20mm projectile than you do on a 13-15mm projectile.


Yes, also all reasons a shorter, wider projectile would be more useful for chemical filler than a longer, smaller caliber one of similar mass. (space occupied by fuzing components would be part of that too)

On top of that, larger barrels have better wear properties, the drawbacks being heavier barrels and lower sectional density of the projectiles. (ammunition may or may not be heavier as well, that would depend more on the projectile weight, case weight -if any dimensions change, and propellant charge)

Something in the 14-17 mm range wouldn't be as good as 20 mm for HE/I but still considerably better than 12.7 mm, and even 13.2 mm would have some noticeable advantages over 12.7 mm. (larger caliber, shorter projectiles would probably be preferable on the whole -say around 17 mm with similar proportions to the Ho-5 or Shvak shells, though AP performance would diminish at range due to poorer ballistics even if velocity didn't drop)




> a lot depends on timing, at certain times the Oerlikon guns required lubricated ammo (read greased or at least wax coated) which was frowned on for aircraft use. Grease/wax at 60 degrees F vs Grease/wax at _minus_ 30-40 degrees let alone 60 degrees below. What is tolerated aboard ship/s is not tolerated as much in aircraft or on land. Please remember that while war was looming they weren't shooting just yet and what was _desirable_ often held more importance than it did once the shooting started. Different countries may have had different standards of reliability.
> Please remember too, that in the case of Great Britain, they were not buying just for use in the British isles but for use through out the Empire. ANY gun or ammo had to tolerate a wide range of climatic conditions.


Indeed, and there may be a better argument for some other countries adopting the oerlikon gun (plus cases of engine mounted guns would avoid some of the temperature related grease/wax issues).

The Oerlikon guns may have been more appealing in the US, especially for the USN given the typical low to medium altitude use and climates usually in play. (USAAC aircraft focusing mainly on coastal conditions would tend to fare better there too) Part of that is in hindsight given the awful trouble the hispano gave in US service, but the more practical pre-war advantages of lighter, lower recoil weapons intended for wing mounting would be significant as well. (especially with the USN more desperate for converting to 20 mm) The FFF may have been unattractive, but the FFL would be in a fairly reasonable performance range. (much better than the Army's M4 37 mm gun and similar to the ballistics of the 23 mm Madsen -slightly higher velocity but lower sectional density)

That said, larger caliber developments of the M2 Browning was probably the bigger missed opportunity. (also hindsight, but given the bureaucratic issues tied to US 'cannon' -guns above .60 cal- being manufactured with looser -artillery- tolerances, not only might the Oerlikon mechanism have fared better, but any light cannon staying at or below .60 cal would also avoid that problem and have tolerances akin to the .50)




> There is a lot of talk about re-chambering and necking out (or down). Some of these guns had a few MM to spare as far as overall cartridge length goes and some did not. The designation, such as 23 X 106 does not tell you the over all length of the round, it tells you how long the cartridge case is without projectile. It also does not tell you haw fat the case is (diameter of the body of the case). It _sometimes_ tells you how the gun was headspaced (how the cartridge is located in the chamber front to back) The 20mm Hispano case was 24.8mm in diameter and headspaced on the shoulder.


The Madsen 23 mm round was of similar length to the 20x120mm madsen round and I'm not sure on the exact dimensions, but I wasn't expecting it to directly fit into the Hispano, more suggesting that the hispano mechanism be adapted for a new 20 mm gun to replace the older madsen OR that the 20x110mm hispano ammunition be necked out to accommodate the 23 mm Madsen shell at some expense of velocity and possibly reduced propellant charge. (similar compromises to the MG-151 going from 15 to 20 mm)

But that assumes any country could secure a license for even the Madsen shells (particularly the high capacity HE/T rounds with self-destruct). It may have been just assumptions on continued import access to Denmark, but the lack of licensed production does imply the possibility of Madsen's terms being unfavorable or licenses not being offered at all. (granted, reverse engineering the weapons or ammunition could also have been a possibility, particularly after Denmark's capture)

In the case of the Browning, a 23 mm gun scaled up and engineered for the 23x106 mm round, or perhaps adapting the high powered US .60 cal anti-tank case instead would have been useful. (but that just goes back to the broader potential for the Americans to focus on the browning in general ... including scaling it up to fire that powerful .60 cal round in the first place -they went to the trouble of copying the MG-151, but didn't work on scaled up browning derivatives?)

Beyond that, the 'simple' cases of barrel replacements to otherwise similar guns would involve using identical maximum case diameters and base dimensions as well as projectile length/seating that maintained similar overall cartridge length. (so similar to the way the .50 BMG was adapted to 13.2 mm Hotchkiss and 14.3 mm in the .55" Boys) 



> The taper on the .50 cal Browning case is there for a reason, so is the shoulder. They can be changed but eliminating them or reducing them to mere vestiges of what they were is going to play havoc with the guns ability to function without some _major_ development time.


I wasn't suggesting the taper be adjusted, though going much/any wider than the Boys did would mean a more significant change to the shoulder's position or dimensions. But wouldn't the 14.3 mm projectile of the Boys round itself be reasonable to adapt to the existing M2?

15~15.2 mm (60 cal) might have been doable, but the difference between neck and shoulder diameter would be even smaller and might cause problems. (likely widening the neck to 16.2~16.4 mm with the shoulder still at 18.1 mm, that's not much taper) A 17 mm or larger projectile would be a more definite problem and require repositioning of the shoulder and likely more modifications to the gun.






tomo pauk said:


> Looks like the Oerlikon FFF fired a 128 g shell at 600 m/s, the Ikaria MG FF fired the 134 g shell at same speed? The muzzle energy was 23-24 kj. For a 100 g projectile, that would be close to 700 m/s? The MG FFM used a bit smaller propellant charge, the 92 g shell went out at 700 m/s.
> The MG FF didn't ended nearly as heavy as the FFL, but FFL received more development that gradually decreased it's weight from 43 to 34 kg, later to 30 kg. The development of the FFF/MG FF wasn't much pressed on, the only modification being the MG FFM, so the lower recoil could still operate the gun action. The FFL would be as easy/hard to install on the turets as MG 151 or Hispano V?


The lighter, developed form of the FFL combined with the lower recoil and shorter barrel should have made it more practical as a defensive weapon than the Hispano, though bulkier than the M2.



> Since there is a violent opposition for the UK adoption of the 'big bang' Browning (  ), any opinion on how well would it served in LW or USAF/USN?


As above, the US adopting the Boys (or even Hotchkiss) round would be interesting, but more so would be the powerful American .60 cal round. The latter wouldn't be rechambering though, but a complete scaling up of the weapon more akin to what the Japanese did, but likely heavier than the Ho-5 given that .60 cal was considerably more powerful, more powerful than the German 15 mm cartridge as well. (whether they kept it 60 cal or necked it out would be another matter ... or a matter of /when/ as well, given they did just that for the M39 revolver cannon much later)


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## kool kitty89 (May 7, 2015)

Jabberwocky said:


> The FN-Browning was variously advertised at rates of 1000 rpm, 1050 rpm, 1100 rpm and 1200 rpm throughout the 1930s, so I wouldn't view the rate with too much suspicion. The most common figure I’ve come across is the pre-war literature is 1050 rpm, which is the rate the RAF got when they tested the gun in 1938.
> 
> I would consider 1200 rpm to probably be the upper end of the cyclic limit for the gun. A maximum value, rather than an average value.
> 
> The Finns also put a locally built version of the M2 Browning on their Brewster Buffalos and the VL Myrsky. The gun is recorded in Finnish sources as firing at 1000-1100 rpm, further lending credence to the notion that the Browning was capable of being uprated to more than 1000 rpm.


That might explain the preference for synchronized guns with the Finns and some smaller airforces when the American synchronized brownings fared rather poorly in rate of fire. Even if sustained high rates led to problems on the M2, use of higher peak cyclic rates combined with the limits of synchronization may have made for a fairly useful weapon.





Shortround6 said:


> The US had at least three different companies working on the high rate of fire .50 cal gun and each company went through multiple prototypes/versions. It took about 3 years from start of work to to get an acceptable model (the US Standards) and the version chosen had next to NO INTERCHANGEABLE PARTS with the M2 gun. It wasn't simply a lighten bolt and different spring. The High rate of fire guns had to be manufactured as such and no conversion kit to bring older guns "up to speed" was ever issued.


Any idea how that compared with the American development of the Hispano? I know it had some particularly convoluted problems both on the engineering end (including ignoring British suggestions) and manufacturing tolerance end. 



> Some of the American prototypes were much more successful than others and it wasn't a steady progression in rates of fire, some prototypes may have simply shown them _what not to do._
> The US had decided it wanted 1 breakage and 5 malfunctions per 5,000 rounds fired at 1200rpm which may have been setting the bar a bit too high. The Russian 12.7mm machineguns were not designed to last for 5,000rounds without hte whole gun be replaced.


Though that sounds more like the opposite of some problems the Hispano had ... setting higher standards and tighter tolerances than the 'artillery' class cannon. (of course, the 37 mm M4 was a fairly reliable weapon in spite of being in that same class, if more conservative engineering than the Hispano itself, and a fairly poor performer for its size and weight)



> The American .50 was also a barrel burner. Long bursts could take out some of the rifling. Even the 800rpm guns were _supposed_ to be limited to initial 75 round bursts and then shorter bursts. And I believe this was with chrome lined barrels.
> 
> A bigger bore will help with barrel life.


As above, allowing high peak rates of fire exclusively in synchronized mounts (where average/effective RoF would still be within practical wear tolerances) could be significant. And yes, I mentioned before that larger caliber projectiles would improve barrel wear and would have been advantages to using the Hotchkiss and especially Boys rounds. (in the latter case using the special high energy high velocity propellant loadings might not be compatible with the existing M2, but more moderate loadings of the same cartridge should at least be more straightforward)


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## Shortround6 (May 7, 2015)

There was an experimental 16mm round based on the .50 cal. It was used in an experimental Cannon/machinegun in the 1939-42 period and was of interest to Lockheed for the P-38. 







From Tony Williams website. Photo shows a variety of cases derived from the .50 browning. 

The gun/ammo was rejected by the Air Force. Details seem to be scarce to non-existent. 16mm seems to be about the max that could be reasonably put in a .50 cal case for use in an automatic weapon. 

Part of the caliber question comes to philosophy or school of thought. The US wanted high velocity for short times of flight and depended on kinetic energy for destruction. Other nations wanted the exploding projectile and were willing to take lower velocity. The Hispano (or guns of that size and power) could combine both. The US went off the deep end and spent _waaay_ to much money and time on extra high velocity .50 cal and .60cal guns. 

The Browning could certainly be scaled up to take larger rounds as the Japanese well showed with 30mm Browings (weighed 60kg or over) But again it depends on what the guns are wanted for. Fixed gun for fighter use or turret mount gun for bomber defense ( and in 1937-39 ONLY the French and British had turrets in service) and turrets ranged from the 30in dia (900mm) one on the Blenheim to the large 20mm turrets on the French bombers (trying to change the drum on the Hispano in combat with the drum outside the turret would have been interesting. 






You aren't going to gain much of anything going from 12.7mm to 13.2 or even 13.9mm. Not enough to show any real difference. In some cases the change in caliber was for manufacturing convenience. Suiting the cartridge and gun to existing ammo production equipment. Nations using 13mm Hotchkiss machine guns could use the same bullet making equipment and the French changed things sometimes just for the sake of changing them so they would be different. The French were in the top 3-4 of weapons exporters between the wars.


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## kool kitty89 (May 8, 2015)

Shortround6 said:


> There was an experimental 16mm round based on the .50 cal. It was used in an experimental Cannon/machinegun in the 1939-42 period and was of interest to Lockheed for the P-38.
> 
> From Tony Williams website. Photo shows a variety of cases derived from the .50 browning.
> 
> The gun/ammo was rejected by the Air Force. Details seem to be scarce to non-existent. 16mm seems to be about the max that could be reasonably put in a .50 cal case for use in an automatic weapon.


Given the rebated rim on that round (16x99RB listed here CALIBRE GROUPS ), I'd hazard a guess at that round being intended for an API blowback weapon.




> Part of the caliber question comes to philosophy or school of thought. The US wanted high velocity for short times of flight and depended on kinetic energy for destruction. Other nations wanted the exploding projectile and were willing to take lower velocity. The Hispano (or guns of that size and power) could combine both. The US went off the deep end and spent _waaay_ to much money and time on extra high velocity .50 cal and .60cal guns.


There's also the odd case of the slow firing, low velocity 37 mm M4, and a complete lack of any middle ground between the .50 browining and Hispano and bulky, slow firing, low velocity M4.

Why the USAAF was willing to compromise on the M4 and even seriously consider it a capable air to air weapon and even continue its development is a bit bizarre given the apparent obsession with velocity. (it's also one case where the low velocity was a serious complain from pilots using it, particularly with its mis-matched trajectory with the .50s and .30-06 rounds carried alongside it on the P-39)

In the mid/late 1930s the US Ordinance Department did pursue 23 mm cannon development with a number of designs:
CAL90

Interestingly, it's mentioned that Colt proposed adapting the short recoil Browning machine gun mechanism to the 23 mm (.90 cal) requirement, but that proposal was rejected. The low (130 RPM) cyclic rate is also rather strange. The (apparently) API blowback based T2 cannon seems to have been the most promising with a rate of fire close to that of the Oerlikon FFS (400-450 rpm) and somewhat better than the Madsen's 360 rpm. 

The rate of fire, weight, and caliber requirements were all met by the Madsen cannon itself, though the 869 m/s muzzel velocity was no. (the 23 mm madsen only managing 720 m/s -still far better than the M4's 610 m/s)


Aside from that, looking at the 20x110 hispano and 20x120 madsen rounds side by side here:
http://www.quarryhs.co.uk/20mm2.jpg

It seems like it might actually have been more straightforward than I was thinking to adapt the madsen cartridge to the hispano, or the 23 mm madsen shell to the hispano cartridge.


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## Shortround6 (May 8, 2015)

The US was certainly _interested_ in bigger guns than the .50 cal. It just takes 4-6 years to go from the start of a project to getting a working gun into production and that assumes the thing was going to work to begin with. Since high rate of fire guns depend on a balance of bullet weight, propellant, cartridge length, gun weight (and component parts) and often cam surfaces (belt feed mechanisms often depend on a stud traveling in a track to turn the forward and back motion of the bolt into a sideways motion to pull the belt), even quality of the brass (or steel) cases. getting everything to work together at the desired speed often takes a while. Firing single shots is often no problem 

The US had built several of the largest prototype bombers in the world (B-15 and B-19) and was certainly interested in how to shoot down an enemy bomber of similar size. But shooting down such large (but slow) bombers was a much different problem than shooting down fighters or twin engine aircraft. 

The thread is about the uses of the big Browning pretty much as it stood or small changes. Major changes, for most countries, would come to late. Like a lot of things, timing was key. A better gun/ammo that shows up just a few months after contracts are signed and tooling ordered for a slightly lower performing gun may be rejected because of the delay in getting _any_ guns it would cause by switching. 

The Japanese tried to get around the fuse issue in their 12.7mm ammo by using a more sensitive explosive and/or using a small amount of trapped air and the heat of compression from impact to start the detonation process. A number of Ki 43s were fitted with very gauge sheet metal (or thin armor) troughs in front of the guns and over the engine because of the number of premature detonations as the rounds left the barrel. 

Exploding 12.7-16mm bullets/shells may very well be more effective than non-exploding ones. But they are going to very much more expensive and not much cheaper than the more effective 20mm shells. The 20mm shells need more material but roughly the same amount (o r slightly more) of machining and assembly time. 
There is no law of nature of physics that says that more countries could not have adopted the Browning or forms of it and what ever problems there there were could have been solved. The question becomes _if_ they could have solved in a timely manor or not affected other things. 
The British saw the Hispano in 1936 and finally decided on it in 1938, it took about two years to get it into service and it still needed modification/s. Between 1936 and 1938 they were getting the .303 Browning into production. Getting the Vickers K gun into production for the RAF ( and FAA). The Army was getting Bren guns, 7.92 Besas and 15mm Besas into production. Perhpas the last could have been ditched and the big Browning used instead? Navy was going for the Oerlikon (and the guns were not interchangeable in use even if the projectiles were, different maintenance requirements and such). Other countries were in the same boat, You did have salesmen from various countries/companies trying to flog their products around not only Europe but South America and Asia. Many times the "products" were not trouble free and the salesmen were looking for development funds as much as selling weapons as they would become known _during_ WWII.


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## kool kitty89 (May 8, 2015)

Shortround6 said:


> The Japanese tried to get around the fuse issue in their 12.7mm ammo by using a more sensitive explosive and/or using a small amount of trapped air and the heat of compression from impact to start the detonation process. A number of Ki 43s were fitted with very gauge sheet metal (or thin armor) troughs in front of the guns and over the engine because of the number of premature detonations as the rounds left the barrel.


Wasn't that design an extension of the older PETN filled unfuzed exploding .303 british rounds? (I don't think they were much used by the british but more by Japan)

The British used self-detonating compositions in their incendiary shells though. Using hot burning low explosive (flash powder like) compositions seemed to be the effective compromise that both the Germans and British settled on for rifle caliber rounds, except the germans resorted to the relatively costly method of fuzing those incendiary rounds even in 7.92 mm, unlike the Mk.VI/VII .303. (or similar Vickers .50) And of course, 13 and 15 mm German incendiaries were fuzed as well. (though they seem simpler and certainly smaller and more compact than the British Mk.V ) 
The 7.92 mm B-patrone explosive incendiary 'spotter' round seems to have gotten away with a fairly simple impact fuze using a firing pin and tetryl charge.

Bad Request

That seemed to allow a very good ballistic shape as well, compared to most cannon shells and fuzed HMG shells. I'm not sure why such wasn't employed on larger designs. (perhaps impact sensitivity relative to the larger rounds, or more complex fuzing required -especially for detonating relatively insensitive high explosives -except tetryl should have been plenty useful as a primary detonator, so perhaps just the smaller mass and higher velocity of the 7.92 mm rounds making more reliably jarring impacts)



> The British saw the Hispano in 1936 and finally decided on it in 1938, it took about two years to get it into service and it still needed modification/s. Between 1936 and 1938 they were getting the .303 Browning into production. Getting the Vickers K gun into production for the RAF ( and FAA). The Army was getting Bren guns, 7.92 Besas and 15mm Besas into production. Perhpas the last could have been ditched and the big Browning used instead? Navy was going for the Oerlikon (and the guns were not interchangeable in use even if the projectiles were, different maintenance requirements and such). Other countries were in the same boat, You did have salesmen from various countries/companies trying to flog their products around not only Europe but South America and Asia. Many times the "products" were not trouble free and the salesmen were looking for development funds as much as selling weapons as they would become known _during_ WWII.


Given the british weren't particularly interested in synchronized guns, the oerlikon cannons (and maybe madsen) would seem more attractive with lesser development than the browning anyway. (the same would apply to several other European air forces)

The RAF DID trial the hurricane with some variety of Oerlikon gun but either the FFS or some derivative of the older, heavier Oerlikon S, and in any case they proved unsatisfactory for similar reasons to the early Hispano. (I'd thought it was the FFS, but looking again it could have been something else implying the FFS itself might have been more workable -the FFL should still have been less troublesome, the FFF more so but that wouldn't have near the AP capability the Air Ministry wanted ... though if it was the only weapon trialed that actually functioned reliably in the Hurricane, it may have merited a re-think)


For defensive mountings, the .50 vickers might have been more seriously considered along with potential replacements. (browning derived or otherwise -something like the Scotti gun wouldn't be too bad, the Browning derived Ho-103 was faster firing though given the Vickers K managed similar rate of fire to the M1919, scaling that up to .50 Vickers might have been particularly useful)

I believe the .50 Vickers aircraft gun was already 24 kg with similar 700 rpm to the Scotti, if more jam prone. (but again should be easier to deal with in turret/flexible mount, and preferably would be replaced with a better gun later on) The Japanese pushed their .303 vickers up to 900 RPM, so maybe there'd be some potential for improvement on the .50 as well, in the interim?

The only other advantage of the .50 vickers was its more satisfactory performance than the older M1 .50 cal browning and lack of licensing required for production. (that and being belt fed, but the .303 vickers had that advantage over the Lewis and Vickers K as well)


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