Alternative light and anti-tank guns, 1935-45 (3 Viewers)

[tomo pauk]

The topic of making the most out of a medium velocity 75 pops up again, with several options for 75mm kan m/41 involving 5 or 10 caliber longer barrels, a new propellant load within the same case or a combination of both. OG gun shoots a 6.3kg proj at 590 m/s, between 75 M2/Mle 97 and M3. Hot load takes it straight to 625 m/s. 5 cal extension adds 25 m/s and 10 cal 50 m/s. The kan m/41 can be brought to French 75 640 m/s class or to an intermediate between 640 and 700 m/s class.

Americans during the ww2 were making the longer-barreled versions of their 75mm guns, that ended up on the Shermans. The increased MV by ~45 m/s gotten them about 10% of penetration. Soviet did the same for the guns of their tanks, reverting to the AP performance of the ZiS-3 gun.
One of the results was that penetration at 1000m was same as it was before at 500m with the shorter barrel.

Obviously, upping the OG French 75mm would've followed the suit here, and I'd suggest the hot-loading the charge ASAP, indeed as what the Swedes were calculating. My even more cunning plan would've been that the French go with the 'baby Pak 36' idea - upgrading the 75mm to fire the AA ammo, that went to 700+ m/s.

 

[Elan Vital]

Lurking at the Swedish archives now, aren't you
At any rate, getting to 900 m/s with a 57mm recoilles rifle is amazing.

Just re-reading the articles from the Swedish Tank Archives. There are some nice postwar articles about subcaliber ammo as well.

Americans during the ww2 were making the longer-barreled versions of their 75mm guns, that ended up on the Shermans. The increased MV by ~45 m/s gotten them about 10% of penetration. Soviet did the same for the guns of their tanks, reverting to the AP performance of the ZiS-3 gun.
One of the results was that penetration at 1000m was same as it was before at 500m with the shorter barrel.

Obviously, upping the OG French 75mm would've followed the suit here, and I'd suggest the hot-loading the charge ASAP, indeed as what the Swedes were calculating. My even more cunning plan would've been that the French go with the 'baby Pak 36' idea - upgrading the 75mm to fire the AA ammo, that went to 700+ m/s.

I think the reason they did not hot load the Mle 97 directly for full-bore ammo is that the recoil system was already close to the limit (some leeway given that the canister ammo has the greatest momentum and not AP).

Dunno if the chamber can be redone with AA cartridges. In the early 30s an AA gun firing piece was directly mounted on an arty mount. By the time it mattered the more efficient 700 m/s class firing piece was already an option.
Incidentally, I know where the plans of all (6 IIRC?) Havre/AHE 75mm field/AT gun studies from 1938-40 are, which may normally include this firing piece. Will be on my list for any future visit.

The Swedes did think about something like your proposal, mounting the patrone m/30 (of the AA gun?) on the kan m/41, but this would be too long in the tank.

 

[Shortround6]

Americans during the ww2 were making the longer-barreled versions of their 75mm guns, that ended up on the Shermans.

Yes and no, The 75mm field guns were 36 calibers in length, The US shortened the barrels to 31 calibers on the M2 tank guns, Then lengthened them to 40 calibers on the M3 guns.
Difference in performance between a 36 caliber barrel and 40 caliber barrel????

Tank guns generally needed new recoil systems, no room for the barrel and breech to move 4 1/2 feet (French 75mm) when fired.
Now not only is there R & D to be done on the recoil system, you have to figure out how to package it.
And once you have it working you have to figure out if the tank hull and turret will stand up to it. French 75 was a light gun for it's performance and it was the long recoil that allowed that. It traded long recoil travel for reduced peak recoil load.
Muzzle brakes help. But if for some reason (desired overhang?) length of tube is restricted the designer may have to decide between actual tube length and overall length.

Soviet 76mm M36 gun was already using higher performance ammo than the French 75, around 80-100ms for same weight projectile. and may have been a more suitable weapon for upgrading.

upgrading the 75mm to fire the AA ammo, that went to 700+ m/s.

The French AA guns that had 700 m/s velocity used cartridge cases 518mm long.
Maybe you can ream out the chamber?
If the case is bottlenecked you may need a new breech block.
You are going to have up grade the recoil system.

Swedes did adopt the 75mm AA gun into a tank gun in the 1950s.

26 metric tons. New turret on M/42 chassis/hull.

It was actually quite an undertaking.

 

[tomo pauk]

I think the reason they did not hot load the Mle 97 directly for full-bore ammo is that the recoil system was already close to the limit (some leeway given that the canister ammo has the greatest momentum and not AP).

The muzzle brake would've been required.

Tank guns generally needed new recoil systems, no room for the barrel and breech to move 4 1/2 feet (French 75mm) when fired.
Now not only is there R & D to be done on the recoil system, you have to figure out how to package it.
And once you have it working you have to figure out if the tank hull and turret will stand up to it. French 75 was a light gun for it's performance and it was the long recoil that allowed that. It traded long recoil travel for reduced peak recoil load.
Muzzle brakes help. But if for some reason (desired overhang?) length of tube is restricted the designer may have to decide between actual tube length and overall length.

Since the Shermans used much more powerful weapons than the 75mm, including the ones with a much longer barrel, I have no worries that the new cannons will be too much.
As an AT gun - even less so.

 

[Shortround6]

Since the Shermans used much more powerful weapons than the 75mm, including the ones with a much longer barrel, I have no worries that the new cannons will be too much.
As an AT gun - even less so.

AS a tank, the Sherman was under gunned. A 30 ton tank with a 2000fps 75mm gun has no problems if the turret ring is up to it.
With more powerful guns and/or lighter vehicles things start getting a little more difficult. A 30 ton tank can still stand up to much more powerful guns.
When you are trying to design 2-3 ton towed AT guns things get harder, even with the longer recoil distances.
And basically the French 75 is a crap gun to try to make an AT gun out of. It is cheap, it is available and????
still thinking
It needs a new carriage and it needs new sights and it should have a new breech block and it should have a barrel that has not been used too much.

 

[tomo pauk]

AS a tank, the Sherman was under gunned. A 30 ton tank with a 2000fps 75mm gun has no problems if the turret ring is up to it.
With more powerful guns and/or lighter vehicles things start getting a little more difficult. A 30 ton tank can still stand up to much more powerful guns.
When you are trying to design 2-3 ton towed AT guns things get harder, even with the longer recoil distances.

2-3 ton towed AT gun - I would not bother with that undertaking.
Self-propelled 2-3 ton AT gun? Now we're talking.

And basically the French 75 is a crap gun to try to make an AT gun out of. It is cheap, it is available and????
still thinking
It needs a new carriage and it needs new sights and it should have a new breech block and it should have a barrel that has not been used too much.

"It is available" is not something that can be dismissed lightly. Same for "it is cheap".
As shown by it's tank-going siblings, it was able to take on most tanks of the day, and it was to the detriment of the French, Americans and Germans that it was not turned into an AT gun much earlier than it was the case with the pak 97/38.

 

[Shortround6]

2-3 ton towed AT gun - I would not bother with that undertaking.
Self-propelled 2-3 ton AT gun? Now we're talking.

????

"It is available" is not something that can be dismissed lightly. Same for "it is cheap".
As shown by it's tank-going siblings, it was able to take on most tanks of the day, and it was to the detriment of the French, Americans and Germans that it was not turned into an AT gun much earlier than it was the case with the pak 97/38.

And how much did such "improvisations" delay the introduction of proper AT guns.
British screwed up. The 6pdr was a better AT gun than the French 75 or it's American cousins.
Now a better AT gun doesn't always mean a better tank gun. Not all targets for tanks are other tanks.

 

[tomo pauk]

????

My idea - not well worded - is that heavy AT guns need to get self-propelled. Meaning a real vehicle that the gun need to be installed on.

And how much did such "improvisations" delay the introduction of proper AT guns.
British screwed up. The 6pdr was a better AT gun than the French 75 or it's American cousins.
Now a better AT gun doesn't always mean a better tank gun. Not all targets for tanks are other tanks.

In both the British and American case, going for the modern 75mm or the equivalent is the introduction of a proper AT gun. Talk something like the ZiS-3 (yes, it was not an AT gun, but it was good in that role). These guns are also much better tank guns than the 37/40/57mm guns. So you save twice.
And not just in money and material, but also in time - that one cannot buy.

Use the money and time saved to came out with the better AP ammo.

 

[Shortround6]

An American 57mm ATG with plain AP shot will go through about the same amount of armor at 1000yds as an American 75mm gun will at 500yds.
The 57mm is not very good at throwing HE as we have been over many times.
The 57mm is about 200kg lighter than the American 75mm M2A3, it is lower and it can cover a wider arc.

Now the US started manufacturing and issuing the 105mm How in the spring of 1941.
There was some argument early due to cost. A new 105mm How cost 3 times what a modernized 1897 on an M2 carriage cost and needed new ammo.
Fortunately the US's late entry into war meant the US went to war (mostly) with 105s in the field artillery units.

The DP or triple threat crap is just that, crap. Handy at times but often the gun/s are not where they really need to be and not doing the job/s they should be doing.
Were Rommel's 88s more valuable shooting up British tanks or defending the harbors where the supplies were being landed?
After the front line troops had the 88s for a while they were useless as AA guns, sights, fuse setters, connections to directors had been lost/broken/damaged so they weren't AA guns anymore.

And yes, for the Americans and especially for the British, stop being cheap and produce APCBC ammo 1 to 2 years sooner. The real need for APCR or APDS (with hindsight) doesn't show up until 1944. Trick ammo does NOT help the French 75 and it's cousins all that much. If you want that kind of performance bite the bullet and design a decent 75-77mm gun.
The American 3in was cobbled together mess of parts from other guns and suffered in addition from poor ammunition and the US fascination ( in their own way) with gadgets and toys.

little armor, except shield, not much ammo, poor conditions for gun crew. Standardized as the M5 but some of the somewhat saner people got it canceled before they built any production versions. This sort of 'stuff' was not a substitute for either towed guns or for real tanks.

 

[tomo pauk]

And yes, for the Americans and especially for the British, stop being cheap and produce APCBC ammo 1 to 2 years sooner. The real need for APCR or APDS (with hindsight) doesn't show up until 1944. Trick ammo does NOT help the French 75 and it's cousins all that much. If you want that kind of performance bite the bullet and design a decent 75-77mm gun.

The HVAP for the L40 75mm gun was supposed to do about 50% better under 1000m than the APC, and about 20-25% more from 1500 to 2000m. That in reality means that it will be able to defeat the Pz-IVH with 80 mm vertical armor front at 1500m, instead of at 1000m - very, very handy already for 1943.

 

[bf109xxl]

Soviet 76mm M36 gun was already using higher performance ammo

What exactly is this cannon? Where did you find this designation? Or is that your creative nickname for the F-22?