German 75mm v Allied 75mm

[vinnye]

Why did the German 75mm guns have so much better performance than any Allied 75mm?
Was it down to barrell length - Pak 40 having 46 calibres = 3.46 metres compared to M3 having 40 calibres or 3 metres?
They both seem to have the same range in weight of shot - from 7 to 14 pounds.
What else made the difference - firing charge, rate of spin?

 

[Shortround6]

Firing charge makes the biggest difference. Rate if spin is almost impossible to measure the difference.

The US and British 75mm tank guns used a straight case 350mm long. The Pak 40 used a straight ( or gently tapered ) case 714mm long. Amazing what you can do with twice the propellant

The AFV guns (Mark IV tanks, Stugs, etc) used a bottle neck case 495mm long but fatter in diameter.

Short German 75mm (L24 used in early MK IVs and Stugs) used a case 243mm long.

Check this website for A LOT of information.

BOOKS BY ANTHONY G WILLIAMS

 

[davebender]

Firing charge and barrel length work together. You need longer barrel to take full advantage of more propellant. KwK42 cannon shells fired by Panther tank had even more propellant to take advantage of very long 7.5cm/70 barrel.

Ammo quality is important too. Germany made some of the best shells including APC, APCR, HE and HEAT.

 

[tomo pauk]

We can note that USA, UK and USSR did have 76.2 mm/3 in cannons/ammo in use, too (soviets and UK have had 2 of 76.2mm, notably different both in capability and numbers produced). The mere 1.2mm does not tell the story - it was, as in case of the 2 more powerful German cannons, the bigger casing using more propellant. The UK and USSR 76.2mm AAA ammo never arrived at AFVs (Soviets tested the gun for the AAA ammo, though), the lower power Soviet 76.2mm ammo (equivalent in power with French/US/UK 75mm) was used for ZiS-3 cannon and in T-34-76 and KV-1 mostly.
The most powerful Allied 3in class gun was the famous 17pdr, and we can also note the 75 and 77mm HV guns, equivalents (in power) with German 75mm L43/46/48.
US 3in was an 'legacy' gun, later the US built 76mm gun (for AFVs and as AT towed gun), both capable using same ammo as the 3in AAA? Again, equivalents in power with German 75mm L43/46/48.

The main and major advantage of the German 75mm stuff was it's timely arrival at war theaters.

 

[Shortround6]

US 3in was an 'legacy' gun, later the US built 76mm gun (for AFVs and as AT towed gun), both capable using same ammo as the 3in AAA? Again, equivalents in power with German 75mm L43/46/48.

The US 76mm used the same projectiles as the 3in gun but used a shorter, smaller case operating at a higher pressure to get the same ballistics.

 

[nincomp]

To narrow down the the search on Anthony Williams website (link from Shortround) here is a page that shows the WWII German tank/antitank shells next to the Allied ones. My first response was "Wow, the allies had teeny weenie shells when compared to the German ones."
Scroll down to the picture of "German British WW2 Tank Gun Ammunition" in the following link. You will see that the British 17 pounder (76x583R) is the only Allied shell even close to the larger Axis rounds. Note the size of the 75mm round to the left of the 17 pounder. That was what most Sherman tanks used.
tankammo2

Most Americans do not know that the British upgraded many Sherman tanks with the 17 pounder in order to take on the Panthers and Tigers. They encouraged the US to do the same. Look up "Sherman Firefly." The Americans disagreed and refused to follow the British example.

After landing in France, the Americans changed their minds and desperately wanted the Fireflys, but there were not enough to go around. To make matters worse, it was a very nasty surprise when the Americans discovered that the new, more powerful 76mm guns fitted to some of their Shermans were not nearly powerful enough to battle the larger German tanks on equal footing. The American commanders had previously been assured otherwise.

 

[tomo pauk]

The US 76mm used the same projectiles as the 3in gun but used a shorter, smaller case operating at a higher pressure to get the same ballistics.

Thanks

 

[davebender]

An expensive upgrade as it involved much cutting and welding of metal by hand. I wouldn't be surprised if Firefly Sherman total cost (original tank price plus modifications) was as much as a German Tiger tank.

To make 17 pounder cost effective the Chrysler tank plant would need to design turret and hull for that weapon and mass produce them that way. IMO that's a fine idea but Chrysler needs to begin design work for Sherman / 17 pounder variant during 1942 so they will be rolling off assembly line by end of 1943.

 

[tomo pauk]

An expensive upgrade as it involved much cutting and welding of metal by hand. I wouldn't be surprised if Firefly Sherman total cost (original tank price plus modifications) was as much as a German Tiger tank.

That's a bit too much, Sherman Firefly ending up as expensive as Tiger? Why we should consider cutting and welding as an hugely expensive exercise to get the Firefly up running?

 

[davebender]

I have yet to see a price or man hour requirements for Firefly conversion. Have you?

 

[Shortround6]

And yet you estimate it to be equal to one of the most expensive tanks of WW II based on what?

 

[fastmongrel]

The major turret mods were fitting a hatch for the loader and welding a box on the back for the radio. Dont know how thick the roof plate was on a sherman (say half an inch for argument) but the main difficulty is not cutting the metal which a good man with a gas axe could do in an hour or so but making sure the turret doesnt warp and throw the turret race out of alignment. The major mods for the 17 pounder were iirc a new mantlet, new recoil and run out cylinders and new ammo boxes. I believe turrets were modified and then fitted to new hulls which had the original turret removed co-drivers position removed and new ammo boxes fitted, these spare turrets then went through the modification shop and ended up on another tank.

 

[nincomp]

To make 17 pounder cost effective the Chrysler tank plant would need to design turret and hull for that weapon and mass produce them that way. IMO that's a fine idea but Chrysler needs to begin design work for Sherman / 17 pounder variant during 1942 so they will be rolling off assembly line by end of 1943.

No argument from me. From what I have read about the issue, General McNair, and probably others, kept such changes from happening. Gen. McNair believed that a tank's job was to support the infantry and the job of destroying enemy tanks fell to towed anti-tank guns and tank destroyers. Even after Tiger 1 tanks had appeared on the battlefield, he tried to cancel the M26 Pershing tank program, since in his mind, heavy tanks were pointless.

One of the many problems with this doctrine was that advancing Allied tanks would come under fire from German tank and anti-tank weapons long before towed guns or even the tank destroyers could be moved up to the battlefield. Even when the Allied weapons were in place, the guns from Panther and Tiger Tanks as well as German tank-destroyers and towed 88mm cannons could shell the Allied weapons while staying out of range of those weapons.

It is somewhat ironic that General McNair was killed (by allied bombers) before the massacre of large numbers of allied tanks in Europe conclusively showed that his tactics were flawed. My (Canadian) father-in-law was watching at Caen when the British and Canadian tanks crossed the river and were largely wiped out. These forces did have some Fireflys, but they were too few to knock out their largely concealed opponents. Unfortunately, the Fireflys were easily distinguished by their long barrels with muzzle breaks and were targeted first by the German weapons. The tank commanders would have given almost anything to have had a Pershing tank at that time. My Father-in-law has often spoken about seeing one allied tank after another being destroyed.

There was no way in hell that he would ever volunteer to get into a Sherman Tank. Even on those occasions when he came under fire, he felt that his chances were better in a jeep.

Although this is straying from this thread, while I was doing an errand with my father-in-law this morning, he mentioned how fond he was of the Tiffys when they came in and attacked ground targets. In addition, he actually did see one Me262 in the air and wondered what in the hell it was.

If anyone wants to get some information from a former Canadian Colonel who worked for Montgomery, you had better ask soon. He is 95 and his short-term memory is getting worse. All of his "war buddies" are already gone.

 

[davebender]

If that were true most Sherman tanks would have 105mm main gun. About 3 times as much HE as 75mm shell. Or perhaps 90mm/40 cannon which provides a nice increase in HE payload and adequate armor penetration.

I think it's more likely Gen. McNair and others like him were afraid to risk failure (and his General's pension). So they stuck with a tank/gun combination which was adequate and already in production.

 

[Shortround6]

At one point in the continual flip-flops that the tank production planners engaged in, 3/4 of all Shermans were to be armed with the 105 "howitzer" and 1/4 with the 76mm gun. Then they realized the Shermans might actually have to fight German tanks.

There was NO 90mm/40 cannon available. And to design and build one would have been stupid even by US tank Ordnance standards. They had a perfectly good 90mm/L53 already available.

 

[vinnye]

So the question now is - did the US ever put the 90mm L53 ,that they had available into the Sherman?

 

[Shortround6]

As the M-36 tank destroyer.

One model used the hull of the M-10. another model used the Hull of a regular Sherman.

Please note that this vehicle seems to have been upgraded with the gun from either the M-46 or M-47.

 

[davebender]

Kanonenjagdpanzer - Wikipedia, the free encyclopedia
Main armament
1 x Rheinmetall BK 90/L40 90mm anti-tank gun

According to Wikipedia this cannon was from U.S. M47 tank. Did the German Army shorten it to make it fit the Kanonenjagdpanzer?

 

[Shortround6]

I would be very careful about that.

The gun certainly used US ammo but using old barrels seems a little much. Re-manufactured perhaps?

The US guns were good for 700 EFC rounds (Effective Full Charge) so depending on training might have had a fair amount of wear. Not sure if a different recoil system was used.

Rheinmetall also developed new ammo for the gun. Two different HEAT rounds and a HESH round. Apparently kinetic energy rounds were not used (or quickly replaced) in the Kanonenjagdpanzer as the primary AT rounds meaning a shorter barrel could be used. The HEAT projectiles being 5.74kg and the HESH projectile 7.45kg. The WW II 90mm AP projectile weighed 10,9kg.

 

[kettbo]

If that were true most Sherman tanks would have 105mm main gun. About 3 times as much HE as 75mm shell. Or perhaps 90mm/40 cannon which provides a nice increase in HE payload and adequate armor penetration.

I think it's more likely Gen. McNair and others like him were afraid to risk failure (and his General's pension). So they stuck with a tank/gun combination which was adequate and already in production.

The 75 worked fine in the M-3 Grant, so it was kept in the follow-on M-4. Just fine for bunker busting, MG position neutralization, and the like. US Doctrine was tanks were for iInfantry Support and break through. Those pulling the production strings needed quantity/ease of manufacture, reliability, size and weight to fit rail and ships...yes, must cross the Atlantic on a freighter. OH, they need to be able to be lifted by common cranes. Germans blew the permanent bridges, must be able to cross temporary or second rate bridges. A lot more to this than meets the eye initially.

The US 76.2 did not do well shooting HE. Shell was less effective. The AP rounds weren't all that great until HVAP vs Panthers and Tigers, AUG 44, but in short supply, most going to AT units. But the regular AP round performance was on par with the German 75mm rounds, Pzgr 39. The Pzgr 40 was not common, wish I had more details on the availability (or lack thereof)

Lots of Shermans, more Shermans in an Infantry Division than most Panzer Divisions had tanks

The M4(105) became available Summer of 44. Platoon of six for Fire Support for the Armored Bn. Not horribly effective vs tanks, looping trajectory. The 105 HEAT round, at closer range where hits are more likely, could do some damage. Ammo capacity would be a problem for general fitment. Then the logistics of planning for use of the rounds, manufacture, etc. Damn Bean Counters!