Alternative light and anti-tank guns, 1935-45 (2 Viewers)

[tomo pauk]

The successful, at least in terms of huge production volumes, WWII era AA guns in this size class, in particular the German 88 flak 18/36/37, UK 3.7", US 90mm, USSR 85mm, all had MV between 790-840 m/s.

Going for >1000m/s with 1930'ies metallurgy was probably biting off more than one can chew.

Note that I've said AA and AT guns, too.

While indeed the metallurgy of the early 1930s will be hard pressed to reliably muzzle velocities going well above 1000 m/s, the metallurgy of the late 1930s and early 1940s might've support the 1000-1080 m/s MV range. Germans were pushing towards 1000 m/s already by 1935 with the naval Flak, while having the 70+ calibers long 75 and 88 mm guns in the pipeline. Soviets were pushing with the 57mm ATG.
I'd suggest that we don't criticize the French for trying to make what it seemed as a logical next step, but rather to criticize them for not making the 800-850 m/s 'step' across the board and in good/great numbers from the late 1920s/early 1930s. Like, for every gun of such ballistic qualities, they have had in their warehouses perhaps 3, 4 or 5 guns of very sedate ballistics, talk 550-720 m/s (and these making 700+ m/s was a rare breed). It is not like they didn't know how to make good if not great guns - their naval and casemate guns were often with MVs of 850 m/s and above, so were the 25mm ATGs and (rare) AA guns - however, the land-based cannons and heavy AA guns were left behind in that regard.

People might raise a point of the barrel life, and rightly so. However, in a real war, the high MV AT guns will probably be destroyed before the barrel is worn out, while the removable barrel lines were a known quantity. Also the whole replacement barrels.
What might come as a bane to the mass introduction is the high price for the very long-barreled guns, and the ability of industry to churn out the required number of barrels.

 

[marathag]

People might raise a point of the barrel life, and rightly so. However, in a real war, the high MV AT guns will probably be destroyed before the barrel is worn out, while the removable barrel lines were a known quantity. Also the whole replacement barrels.

bit of info I collected over the years


M3 75mm 24000 rounds APC M6 aircraft 6000 rounds

M1A1 76mm 2000 Rounds HVAP

M3 90mm 900 rounds

M41 90mm 1500 rounds

KwK 37 75mm L/24 12-14000 rounds

PaK 40 75mm 6000 rounds APC

KwK 42 75mm L/70 800 round APCR
2-2400 APC

CN 75-50 150-200 rounds

17 pdr APDS 600 rounds

20 pdr sabot 120 rounds

D-10T 100mm 800 rounds

D25T 122mm 200 rounds A-19 similar

 

[Elan Vital]

this was a very promising path, it just didn't have enough time. It really needed the tungsten carbide core to work.
Using a steel penetrator only works at rather close ranges. The small steel projectile just sheds velocity too fast for longer range work.

I have checked and it's confirmed Brandt had worked on tungsten carbide cores "of high density" already in the 25mm caliber in June/July 1937. The central state laboratories were to inform him of tunsgten production/acquisition potential in France as well as machining processes for tungsten carbide to help him in his endeavour. Thinking about it, the transfer of a tungsten mine's ownership to Brandt before the war (snatched by the Germans after the defeat before it could become operational) might be related to this.

More realistically, the likely main supplier of a hypothetical French tungsten ammunition effort in 1941-43 would probably have been Canada which produced a lot in WW2, to the point where the American industries couldn't refine it all.

 

[bf109xxl]

bit of info I collected over the years

D25T 122mm 200 rounds A-19 similar

According to the maintenance manual for the D-25T barrel wear should be checked after every 250 rounds. Could you please specify your sources?

 

[marathag]

According to the maintenance manual for the D-25T barrel wear should be checked after every 250 rounds. Could you please specify your sources?

Something from 10-15 years ago, when I started making a list. So many links have disappeared since then.

 

[bf109xxl]

Something from 10-15 years ago, when I started making a list. So many links have disappeared since then.

I have an appendix to a certain textbook for students' military training, where for the A-19 the service life is specified as 1200-1500 rounds, and this service life is determined by the extension of the charging chamber. This may be post-war technology, but for wartime I can assume a minimum life of 800-1000 rounds.

 

[Shortround6]

A few posts ago in this thread, I've suggested that the small gas divert tube is added to the small AT gun so the recoil is lowered, since part of the high-speed gasses is pushed backwards. That again means that the whole gun can be lighter due to the lower stress exerted on the weapon. Sorta 10% recoiless gun.
That principle was used on the Croatian RT-20 anti-material rifle, that went under 20 kg despite using the high-power 20mm Hispano cartridge. For comparison, the Solothurn S18-100, that used a lower-powered 'short Solothurn' cartridge, went to 40 kg.
See here the short video of the RT-20 firing (somewhere in Croatia?), with the gunner uttering some cuss

Just ran across this again. You need a lot of gas to actually cancel out much recoil. Most recoil guns used 3-4 times the amount of propellent as conventional gun give the same ballistics.

The formula for recoil is projectile weight times muzzle velocity for bullet momentum (BM) + propellent weight times gas velocity* for gas momentum for the total momentum.

Now you can divide the recoil impulse by the weight of the gun to figure out the recoil velocity of the gun (or the recoiling part/s unchecked by dampers/springs) and then we can figure out the recoil energy (weight of the gun (or recoiling parts) times the velocity squared.

* for most small arms the gases exit the muzzle at around 1200m/s give or take 10% unless the barrel length is really abnormal.

Now to put this into small arms a 7.62 x 51 has BM of 8.32 (after dropping a lot zeros to get a manageable number) and the gas momentum of 3.58 for a total of 11.90
Now it we take 10% of the gas and direct it backward we may be able to reduce the BM by 10% (very optimistic, it is probably closer to 5%) and we can take 10% off the gas momentum
so the new numbers are 7.49 and 3.22 except we have to add in the forward thrust of 10% of the gas momentum so the total becomes 10.35 or just about 87% of the recoil impulse of the gun without the port and tube. You can make the port bigger and tape off more of the gas but there are few problems with that. Lower velocity of the projectile is one. The other problem is that you can't fire the weapon in an enclosed space any more or with walls/obstructions close the back of the weapon.
Actually a decent muzzle brake will reduce the recoil as much or more.

Now we can argue about the gas from the barrel port being higher pressure than the gas at the muzzle which is true but turning the gas rearward costs something and getting the gas back behind the gunner/crew is also going to cost something.

For a 20mm Hispano we have a 128gram bullet/projectile and about 29 grams of propellent. You need to tap off a fair amount of propellent to cancel out the weight of the projectile.

Edit, just watched Ian McCollum's video on the RT20 and he claims that the system cost about 25% in velocity. Lowered MV from about 830m/s to about 620m/s which doesn't make much difference to HE ammo but real reduces the impact of AP. Basically it cuts the Hispano down to about the velocity of a Japanese type 99-1 or German MG FF.
Gun is light for a 20mm but it does use a substantial muzzle brake and recoil is best described as very substantial.

The gas ports cut down the pressure in the barrel cutting velocity and the short barrel also cuts velocity. It worked for what they wanted but it not a system to to use on a kinetic energy AT gun.