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

[Shortround6]

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 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 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.

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.

 

[Piper106]

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.

 

[Shortround6]

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.

 

[kool kitty89]

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) » 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

 

[kool kitty89]

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)

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.

 

[Koopernic]

snip

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

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.

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.

Snip

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.

 

[Edgar Brooks]

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.

 

[kool kitty89]

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)

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.

 

[Edgar Brooks]

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.

 

[Shortround6]

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.

 

[Shortround6]

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.

 

[Greyman]

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.

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.

 

[Shortround6]

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.

 

[Greyman]

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.

 

[fastmongrel]

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.

 

[Shortround6]

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.

 

[Greyman]

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.

 

[Greyman]

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.

 

[Shortround6]

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.

 

[Greyman]

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.