Alternative airborne guns 2.0

[tomo pauk]

The .50 only reached its maximum effectiveness when the design of the Soviet BS-32 armor-piercing incendiary shell was copied, and then its firepower doubled.

Let's not assume that, when people say '.50', that automatically means '.50 BMG of 1939'.

And they should quickly make long 4 row magazines for 100 shells. Length around 80 centimeters is quite managable.

Oerlikon was advertising 75 rd drums (and possibly the 90 rd drums?) when the RAF was shopping for a cannon-armed fighters in the late 1930s; their belt-fed cannons offered to the British in 1930s were not accepted.
Solothurn was making 100 rd drums, that Germans used on the Luftwaffe's 20mm MG C30L guns on the pivot in the Flak role. (see here, scroll down; can be translated)
IOW - there is no need to reinvent the wheel; better spend money and time (the most precious commodity) on making the cannons belt-fed.

 

[Shortround6]

British:
- not giving the .50 HMG a try was a mistake IMO, so this time around they should've try it - there is no reason that each Hurricane and Spitfire already by 1938 could not be armed with 4 HMGs, that each weapon is at least an equivalent of the Italian HMG; the HMG will also be a much better self-defense weapon than a LMG of the era

This may be nit picking. British .5in ammo came in two types. The .5in Vickers, rather widely used, both Semi-Rimmed (export/license) and Rimless (British use) and the .5in High Velocity or class D. Once you add the "0" into the designation you are talking about the .50 Browning

Now for the British in 1938 that means either buying/licensing the the Browning gun and adapting it to use different ammo or using the pretty much the standard US .50 Browning as is.
Which is the quick and easy way. Which means using the pre 1940-41 ammo let alone the M8 AP copied from the Soviets (?).

The only other .5in guns in service existence (not experimental) in 1938 were two Italian guns and the two British Vickers guns and one Soviet gun (the 12.7mm ShVAK), the 12.7mm Berezin was not ordered into production until 1939 and actual production guns showed up in April 1941(?)

The British had no desire to use the Vickers guns in aircraft in locations where the crew could not reach them which rather limits the choice of exiting guns outside of the Soviet Union to the American gun (or Belgian license) and the Italian guns. The Breda-SAFAT or the Scotti, and the Breda-SAFAT weighed the same as the US Browning while using a less powerful cartridge although it did fire a bit faster. 700rpm instead of 600rpm or a bit under.
The Ammo in the British .5in Vickers B and the Italian guns had about the same velocity as the American gun/ammo but the American gun/ammo used heavier bullets. About 29% heavier than the British .5in Vickers ammo.

In 1938 the ".50" cal armament may have been a bit better than the eight .303s but not by much. The problem is that it is heavier and with the 1938 Hurricanes using two pitch props (forget the fixed pitch) that is a problem. Each American .50 is 2.8-2.9 times as heavy as the American .50 and more importantly, the 334 per gun ammo load of the Hurricane is only enough for just under 150rpg for four .50 cal Brownings. Going to 200rpg adds 60lbs and the change of guns adds about 40lbs. Maybe you can make up some of that with just using 4 mounts and not eight even though each mount is heavier?

You don't have higher velocity for better deflection shooting (that shows up in 1940/41).
You don't have good incendiary ammo (Neither does the .303 at this point).
You are only firing about 40 rounds per second, at best, compared to the 144-160 of the eight .303s (faster firing .50 cal Browning also show up in 1940-41)
You have within 1-2 seconds of firing time depending on ammo load out.

Now a late 1941/early 42 Hurricane with four late 1941/Early 42 M2 Brownings has got both the higher velocity rounds and the higher cycle rate guns. US had incendiary ammo but the British didn't use the American incendiary ammo until the M8 showed up later. And in 1941 you have the constant speed props and the Merlin XX engine which means a few hundred extra pounds of guns/ammo is less of a problem.

- as a step up - buy 20mm guns at Oerlikon for the RAF, too, not just for Army and RN; T. WIllians favored (and he still is, if I'm not mistaken) the FFL - again, the Oerlikons should've been available earlier than the Hispano

The 20mm Oerlikon guns were in a state of flux in the 1930s and Oerlikon was not actually shipping guns by the hundreds. Exactly when they hit the published rates of fire with the different guns may be questioned?
Hispano got into cannon business because Oerlikon could not deliver they guns fast enough to equip the French (D 510s?) and they saw room for improvement in the rate of fire.
You can get Oerlikons sooner than you can get Hispano's but are you getting the newest, fastest firing versions?

 

[peceed]

Let's not assume that, when people say '.50', that automatically means '.50 BMG of 1939'.

Vickers .50 was introduced in 1933. In 1935 (IIRC) the RAF decided to arm new planes with 4 x 20mm cannons. The window of opportunity was too short!

there is no reason that each Hurricane and Spitfire already by 1938 could not be armed with 4 HMGs

The best reason is the Oerlikon FF.
There is no point in introducing a transitional weapon when the target one is already available.
Fun fact:
The Germans didn't armour their fighters because they thought everyone would start using 20mm cannons. It wasn't until the heavy losses in Poland inflicted on them by twin 7.9mm machine guns that they were motivated to armour their planes.

Oerlikon was advertising 75 rd drums (and possibly the 90 rd drums?) when the RAF was shopping for a cannon-armed fighters in the late 1930s; their belt-fed cannons offered to the British in 1930s were not accepted.
Solothurn was making 100 rd drums, that Germans used on the Luftwaffe's 20mm MG C30L guns on the pivot in the Flak role.

Even a 60-round drum would not fit completely into the wing, requiring a bulge. A 100-round (or larger) flat magazine would allow for a large supply of ammunition without aerodynamic loss.
BTW it's amazing the French didn't use bigger drums in their fighters.

IOW - there is no need to reinvent the wheel; better spend money and time (the most precious commodity) on making the cannons belt-fed.

The people doing this are different than those who can create a belt feed, and the resources to produce such magazines are microscopic on the scale of war expenditures.

 

[Jabberwocky]

If the UK doesn't go with the HS 404 or the Browning in .303, what about the 1927 Madsen 11.35mm ?

This gun is in some ways a compromise between an LMG and a HMG, so it's not going to fire as fast as the former, or hit as hard as the latter (plus the 11.35 mm round has a relatively low sectional density). However, it has some good features - it's still light-weight (10.5 kg), has a high rate of fire (900-1,050 rpm), a more than decent muzzle velocity (825-880 m/sec) and has a decently heavy round (just shy of 20 grams).

Tony Williams' estimate is that the 11.35mm round was about 2x as powerful as the .303. After adjusting for RoF and other factors the 'gun power' estimate for the Madsen was 32. That's against an estimate of 20 for the .303 Browning, 60 for the .50 Browning and 200 for the Hispano Mk II.

Based on those figures, a battery of six 11.35mm Madsens is going to be a little lighter than an eight Browning .303 installation but is still going to give you a 20% improvement in overall firepower. A battery of eight Madsens is going to be a little heavier, but will increase firepower by about 60%.

Argentina installed the Madsen on it's Hawk 75s. The data I have is:

Gun Length: 1,280 mm
Barrel length: 750 mm
Weight: 10.5-10.6 kg - bare gun weight, not sure about installed weight
Round weight: 19.83 g for API with steel core.
Rate of fire: 900-1,050 rpm;
Muzzle velocity: 825-880 m/sec
Recoil force: 80 kg

 

[tomo pauk]

The British had no desire to use the Vickers guns in aircraft in locations where the crew could not reach them which rather limits the choice of exiting guns outside of the Soviet Union to the American gun (or Belgian license) and the Italian guns. The Breda-SAFAT or the Scotti, and the Breda-SAFAT weighed the same as the US Browning while using a less powerful cartridge although it did fire a bit faster. 700rpm instead of 600rpm or a bit under.
The Ammo in the British .5in Vickers B and the Italian guns had about the same velocity as the American gun/ammo but the American gun/ammo used heavier bullets. About 29% heavier than the British .5in Vickers ammo.

There is many years available for the British to perfect the Vickers guns for the wing mounts. Ammo that is light will be a benefit when the engine power figures and the required firing duration are taken into account.

In 1938 the ".50" cal armament may have been a bit better than the eight .303s but not by much. The problem is that it is heavier and with the 1938 Hurricanes using two pitch props (forget the fixed pitch) that is a problem. Each American .50 is 2.8-2.9 times as heavy as the American .50 and more importantly, the 334 per gun ammo load of the Hurricane is only enough for just under 150rpg for four .50 cal Brownings. Going to 200rpg adds 60lbs and the change of guns adds about 40lbs. Maybe you can make up some of that with just using 4 mounts and not eight even though each mount is heavier?

My suggestion was the Vickers, not the BMG.
The 'big Breda' fired a 3.5 times heavier projectile than the 7.7mm. That is a lot better when the bullet needs to defeat the modern aircraft from the late 1930s and on. I have no intention of having 8 HMGs on the Hurricanes and the like.

The 20mm Oerlikon guns were in a state of flux in the 1930s and Oerlikon was not actually shipping guns by the hundreds. Exactly when they hit the published rates of fire with the different guns may be questioned?
Hispano got into cannon business because Oerlikon could not deliver they guns fast enough to equip the French (D 510s?) and they saw room for improvement in the rate of fire.
You can get Oerlikons sooner than you can get Hispano's but are you getting the newest, fastest firing versions?

Compared with what Hispano was shipping, Oerlikon was bed of roses. British making a deal for licence production of the Oerlikon guns takes no more ingenuity than what the French and the Germans did.
Hispano got into cannon business probably because Birgkit reckoned that he can make a better gun, and because he would not need to pay royalties to Oerlikon for the HS-9.
When compared with the French fighters armed with HS-9, British will be carrying double the number of cannons (although I'd probably want the FFL derivative, not the S derivative). But most importantly, they will have had actual cannons already before the war.

 

[tomo pauk]

Vickers .50 was introduced in 1933. In 1935 (IIRC) the RAF decided to arm new planes with 4 x 20mm cannons. The window of opportunity was too short!

RAF decided to introduce cannons in 1937. The 4 cannon battery on a fighter was decided on a later date.
The 20mm cannon as a bomber's defensive gun will be a bit clumsy, unless the derivative of the light FF(F) is not used, and preferably with the belt-feed mechanism.

The best reason is the Oerlikon FF.
There is no point in introducing a transitional weapon when the target one is already available.

The FF certainly has it's merits. Very light for the calibre, physically small, heavy shell, excellent RoF or the late 1930s. Main shortcoming were that there was no belt-fed version to buy (that can be remedied, while using a bigger drum in the meantime), and the MV wa low-ish at 600 m/s. Outfitting the cartridge with a lighter shell, talk 100g, can improve the MV, while sacrificing the terminal effect somewhat.

 

[peceed]

Argentina installed the Madsen on it's Hawk 75s. The data I have is:

This is a very good replacement for 0.3 (in general), but not its successor in terms of performance.
Actually, only the Germans hit the spot: their Mg 131 is both.

 

[yulzari]

By and large we are missing the target. Almost literally. There are two possibilities. Light/small high velocity if you anticipate coping with nimble enemy fighters and heavy/large but slow to cope with steady bombers. A crude split but essentially correct.

Bombers need a big bang and are both a larger and steadier target. Fighters are faster and more nimble so are a more difficult deflection shot in all 3 axes.

The problem can be dealt with by hardware or software solutions. The hardware solution is to give the pilot/gunner a slower/bigger round and gun to knock down a bomber but has to do so with fewer hits. The anti fighter gun swaps mass for velocity to give a flatter trajectory easing the deflection issues. For the software solution we either train the pilot/gunner until he has mastered deflection shooting or train him to close so near the target that deflection almost ceases to be an issue.

The hardware solution has been addressed above in this thread but not the software one. Pilot/gunner training was one that can be applied with negligible use of capital or time compared with new guns or ammunition. There were certainly some attempts to create ground based gunner simulations of deflection but generally only in two axes at best. Pilots got very little realistic training other than steady flight towed targets (which are very relevant to the bulk users ie anti aircraft ground guns). I acknowledge the common use of gun cameras to examine how well engagements went.

Gunsight innovations attempted to ease the software problem and made a measurable difference

I say all of this not to suggest that gun/ammunition matters are not vital but to point out that the thread subject is one in which they are very relevant. But they exist as part of a whole system in which all the parts contribute towards the ammunition hitting the target.

Give me a peer fighter with a magic huge high velocity round and I would probably miss the target which renders all the hardware irrelevant. Then give me good extended trading in the use of the gun sight and defection shooting and I stand a chance of hitting something. That training also must accustom me to assessing the minimum effective range at which to fire as well as deflection. New pilots typically fire from much too far away. Closing to very close is the software short cut.

 

[tomo pauk]

From what I can discern, a lot of the pilots were ... not good in hitting the moving aircraft. A lot of problems was the inability to deduce the range of the target in the heat of air combat, even with the sights of the time trying their best to help. It took a lot of time and resources to make the pilots became better shots, and even so it didn't worked well for pilot A.B. when compared with pilot X.Y.
Another thing is that one does not know what exact type of aircraft will the enemy be deploying this afternoon, let alone within a few years. So going with the balanced weapon battery made a lot of sense, even if, again, that took many months to arrive at that setup. Case in point being the low-velocity Oerlikon FF guns when paired with LMGs that were with higher MV; same with the MK 108 when paired with the MG 151/20.

Then we have a thing of guns not being designed with much of consideration to the actual fighter that will be carrying them, like a host of Japanese Army cannons, as well as the MK 101 & 103 - all of these required 2-engined aircraft to carry them in a war. Even worse with the German pie-in-the-sky 50-55mm guns, that often fit just one on a 2-engined fighter.

Hence my ... boring idea that the 1st consideration when a new gun is designed is that of the limitations of the platform, that most numerous were the 1-engined fighters with a tractor propeller. The guns with prominent gas tube will demand more space than the guns operating on the short recoil system. Going with the ~700m/s MV as the target, the gun, even if it is a 30mm type, should be able to fit both in the wings as well as as a motor cannon. Even easier to do if the gun is of 20, 23 or 25mm calibre.

Having the common design, that does 850-900 m/s in 20-23mm calibre, and 700-750 m/s in 25-30 mm calibre also has it's merits IMO.

 

[bf109xxl]

Hence my ... boring idea that the 1st consideration when a new gun is designed is that of the limitations of the platform, that most numerous were the 1-engined fighters with a tractor propeller. The guns with prominent gas tube will demand more space than the guns operating on the short recoil system. Going with the ~700m/s MV as the target, the gun, even if it is a 30mm type, should be able to fit both in the wings as well as as a motor cannon. Even easier to do if the gun is of 20, 23 or 25mm calibre.

It seems that all attempts to describe an alternative gun end up describing the NS-23.

 

[tomo pauk]

It seems that all attempts to describe an alternative gun end up describing the NS-23.

Nope.

 

[bf109xxl]

Surely there were studies done in various countries in the interwar period to establish the optimum armament set - at least I know of one by the Soviets. I would be very grateful for any references to their results. It might make sense to take them into account when discussing alternative guns.

 

[bf109xxl]

Nope.

I didn't expect any other answer.

 

[peceed]

It seems that all attempts to describe an alternative gun end up describing the NS-23.

Very close - in the case of ammunition, the design space is from 23x115 to 30x111. Mine shells are preferred because they can have better ballistics at practical distances while maintaining or even higher effectiveness against air targets.

With the same weight, shorter and wider shells are preferred because they provide more volume in the barrel, and thus better use of powder and a larger volume of the case.

There is one rule that everyone should know: there is no point in lengthening the cartridges (proportionally enlarging the case and the shell, maintaining ballistics), because the rate of fire of enlarged is inversely proportional to the length of the cartridges, so the mass of the second salvo does not increase, but the mass of the weapon so enlarged increases proportionally.

These rules have their common sense limitations - longer cartridges can be narrower and provide a greater number of shots,, it is worth using the entire length available in a typical wing to mount the weapon and the ammunition container. A larger caliber shell has a heavier front part and more wasted space by the ogive.
That's why the 20x138, 23x115 and 30x111/30x90 RB cartridges have almost the same total length!
It's worth reaching thresholds of destroying a target with a single projectile - for heavy bombers it was a mineshell with a 400 gram filling, for fighters it can be assumed that it is about 50g PETN with minor corrections for the size of the targets and hitting the wingtips.

 

[Shortround6]

There is many years available for the British to perfect the Vickers guns for the wing mounts. Ammo that is light will be a benefit when the engine power figures and the required firing duration are taken into account.

The British did not bother, that is why they adopted the Browning in .303.
There was an alternative to "perfecting" the Vickers.
Modify the big Browning (scale it down) to fit the British .5 (12.7x81) cartridge like the Japanese did for the Ho-103. Yes it is going to need development work (time). It is not designing a new gun from scratch. You get a smaller (shorter), lighter (23kg?) gun that can fire faster (bolt has to travel a shorter distance).

My suggestion was the Vickers, not the BMG.
The 'big Breda' fired a 3.5 times heavier projectile than the 7.7mm. That is a lot better when the bullet needs to defeat the modern aircraft from the late 1930s and on. I have no intention of having 8 HMGs on the Hurricanes and the like.

The weight comparison are for four .50 cal Brownings vs eight .303 Brownings. Yes the US ammo was heavy.
Weight of .303 Ammo was 28.6 grams per round
.5 in Vickers was 80.5 grams per round.
.50 cal Browning was 119.6 grams per round

There are production variations and some types a bullets varied depending on type. US .50 number is for the early (1930s) ammo. The 1940/41 ammo was around 2 grams lighter due to bullet change.

Disadvantage between the .5 and .50 during the 30s was that the .5 used the lighter bullet and will not have the same penetration or the same long range ballistics. But the cost (installed weight) is more.

Compared with what Hispano was shipping, Oerlikon was bed of roses. British making a deal for licence production of the Oerlikon guns takes no more ingenuity than what the French and the Germans did.
Hispano got into cannon business probably because Birgkit reckoned that he can make a better gun, and because he would not need to pay royalties to Oerlikon for the HS-9.
When compared with the French fighters armed with HS-9, British will be carrying double the number of cannons (although I'd probably want the FFL derivative, not the S derivative). But most importantly, they will have had actual cannons already before the war.

A lot of this depends on WHEN.
Oerlikon was offering the 3 guns in 1920s but..........
F.................................30kg...................300rpm.........................box/drum
AF..............................25kg ..................400rpm.........................drums
FF...............................23-24kg............520rpm.........................drums 1935
German guns changed ammo.
size up
L..................................42kg.................350-380...........................box/drum
IJA 94.........................43kg..................380..................................drum-15
FFL/99-2..................30-38kg...........480-620(?) .....................drums (IJN belt in mod 4)
Size up 2
Oerlikon
S................................62-65kg..................280...........................drums
SS.............................62-65kg..................470...........................drums
FFS (aircraft)...........39kg......................470............................drums
HS-9..........................48kg..................360-420........................drums

There were 3 stages of rate of fire improvements. So when each test (or planned purchase) was made can really affect the out come.

Weights are also a bit of a fudge. Most weight charts do not include the belt feeder on HS guns but then the Oerlikon guns do not include drum weights.
Drum weights for the short FF were
45 rounds......................7.4kg
60 rounds......................8.3kg
75 rounds......................10kg
100 rounds....................12kg
all of these are empty weights.

Note when Brigkit began work the Oerlikon guns were still somewhat heavy and slow firing, offering a lot of room for improvement. Actual test results may not have equaled advertising numbers. What was done in 1940 and later does not count for 1934-37 tests.

 

[Shortround6]

I would note that while the 'mine' shell sounds good in theory it seems to have been much harder to make in practice.
British had recovered many of them in 1940. The British and US did not get any into service during WW II.
NIH or they could not figure out how to do it without an unacceptable scrap rate?
I am sure the British and American metallurgists could figure out the basics and could figure out the alloys. Figuring out the technique (temperatures, speed of the stamps/drawing dies, lubrication (?), annealing processes) is a lot harder.
It might take several years to figure this out, again depending on acceptable scrap rates. Germans were among the leaders in metal stamping. Not all "stamp" guns had the same requirements or needed the same knowledge. Just because you can make stamped headlights and can make stamped submachine guns does not mean you can make stamped belt feed machineguns of acceptable durability.
Cannon shells are single use but failures can be fatal. A shell that comes apart in a barrel is not a big problem in itself. The Problem is when the next shell hits any debris (pieces) still in the barrel and the barrel winds up exploding and this is due to the propelling charge, not the HE content which may or may not add to the problem.

 

[BarnOwlLover]

As far as LMGs, HMGs and cannons, one defecit that the Vickers design had (like all other Maxim and Vickers-Maxim derivatives, such as the Bouchart and Luger pistols) was sensitivity to ammo differences. Those designs were perfectly reliable, as long as they were fed with the spec and quality of ammo they were designed for. Because toggle lock systems had to be basically designed around one main spec of ammo for them to work well. And ammo variances can cause the guns to jam or function erratically.

This is why most planes that used Vickers or Maxim MGs on them had them either used by aerial gunners or were mounted in the cockpits of fighters, to clear any jams that might happen. And that's even allowing for (from what I read) aircraft MG ammo being made to significantly higher quality control standards than infantry ammo. For the RAF, the AN/M2 .30 Browning was more tolerant of ammo variations, which is why it was preferred, as an ammo quality issue was less likely to jam a Browning unless the round was a total dud. And you can't have a pilot clear a jam/re-cock a gun that's mounted in a plane's wing when in flight.

Basically easier to take the AN/M2 .30, rebarrel it to .303, and have BSA make them than deal with improving the Vickers aircraft MGs.

 

[peceed]

Weights are also a bit of a fudge. Most weight charts do not include the belt feeder on HS guns

Yes, it is the reason why the quoted mass of MK.V and MG 151/20 is almost the same.

Oerlikon guns do not include drum weights.
Drum weights for the short FF were
45 rounds......................7.4kg
60 rounds......................8.3kg
75 rounds......................10kg
100 rounds....................12kg
all of these are empty weights.

But there is a catch. You always need some magazine even for the belt, that also has its weight, and drums were extremely convenient as self contained structural elements. The belt also has its non-zero mass. Therefore, the additional cost of the magazine mass in relation to the belt was much smaller.

 

[Shortround6]

This is why most planes that used Vickers or Maxim MGs on them had them either used by aerial gunners or were mounted in the cockpits of fighters, to clear any jams that might happen. And that's even allowing for (from what I read) aircraft MG ammo being made to significantly higher quality control standards than infantry ammo. For the RAF, the AN/M2 .30 Browning was more tolerant of ammo variations, which is why it was preferred, as an ammo quality issue was less likely to jam a Browning unless the round was a total dud. And you can't have a pilot clear a jam/re-cock a gun that's mounted in a plane's wing when in flight.

Actually the US had 3 grades of 30-06 ammo, aircraft (or aircraft machine gun), ground machine gun and rifle. For the US the main difference was the quality of the brass.

Rather difficult to deal with in an airplane.
A broken case in a rifle caused the least reduction in a unit's firepower.

The Japanese used the Vickers design for their 7.7mm belt fed guns but only one airplane (?) used them in the wings and not for very long. A lot of their early fighters used them in the cowl.

 

[tomo pauk]

There was an alternative to "perfecting" the Vickers.
Modify the big Browning (scale it down) to fit the British .5 (12.7x81) cartridge like the Japanese did for the Ho-103. Yes it is going to need development work (time). It is not designing a new gun from scratch. You get a smaller (shorter), lighter (23kg?) gun that can fire faster (bolt has to travel a shorter distance).

Works for me

Disadvantage between the .5 and .50 during the 30s was that the .5 used the lighter bullet and will not have the same penetration or the same long range ballistics. But the cost (installed weight) is more.

'Long range ballistics' term was pretty much an oxymoron for the airborne guns of ww2. Anything beyond 400m was also beyond the 99% pilots' abilities in the era before computerized sights and ranging radars.
I'm not sure where the .50 BMG entered the chat - I've simply noted that the .5 Vickers will out-penetrate the .303 by a good margin. Difference will be even greater if the projectile is required to 1st negotiate a sheet of dural at a sharp angle before it is required to defeat something else.

A lot of this depends on WHEN.

There were 3 stages of rate of fire improvements. So when each test (or planned purchase) was made can really affect the out come.

The earlier, the better. But even in 1935 is okay.
I hope that it is okay if the British (or the other people) are not required to stick with the cannons from 1920s for the late 1939. Or that they improve the late 1930s designs during the war.

What was done in 1940 and later does not count for 1934-37 tests.

If this is not a crucial endorsement for the Oerlikon and not for Hispano, I don't know what it is