Armor vs Firepower

57mm That standard 57mm a/t gun in the U.S. Army was the British 6pdr, the design was given over under Reverse Lend Lease. The only real difference you can see IIRC is the shape of the side shields.

 

RT, and tango yankee

 

After reading John Buckley's fine book on British armor in Normandy, I have to think that the main factor in tank design by 1943-4 was the gun, not the armor. By 1944 all major combatants had guns that could penetrate most armor at most angles, no matter how thick. People talk about the 88, but the British had the 17 pdr with APDS and we introduced the 90mm. At 500 yards even a 6 pdr with APDS could penetrate over 100mm of vertical armor. There was also an upper limit on how much armor a tank could reasonably carry without overburdening the chassis and overstraining the engine. When you look at it, British-designed tanks in early '44 were not badly armored. The latest marks of Churchill were up to 152mm on some frontal surfaces, and the Cromwell got more plates to bring it up to 101mm. The Sherman was more of a problem. I have read that the track links and sandbags added by the crews did little but help morale and added more weight than the tank could carry comfortably.

Speaking generally though it was less the armor than the gun that put the Allies a stroke down in early '44. They simply had too many tanks with the medium velocity 75mm, which was not ideal for tank to tank combat (less penetration than the 6 pdr, actually). But as Buckley points out the Allies had what seemed like good reasons for standardizing on the 75 in 1943. In Tunisia they had found that tanks fought German tanks less often than they fought German infantry and artillery (including AT guns), and for that sort of work a gun with a good HE round like the 75 was much more useful than the 6 pdr. And of course Phylo is right in pointing out that the AT gun was often the most serious enemy of a tank.

 

sounds logical, TerryD [TD ].....kind of hard to believe they [ tank crews AND higher ups ] would not want a bigger gun...what did the tank crews say?..I take it the Shermans were knocking out the PIVs somewhat ''easily''?

 

Well, tank crews DID want a bigger gun. British crews had been asking for bigger and better guns ever since 1941, and they did get them progressively--the 6 pdr, the 75, finally the 17 pdr. The problem, as Phylo says, was lead time. In this respect the Allies lost some ground at least twice--first in 1940 after Dunkirk, when the British had to get anything they could make into the field irrespective of whether it was obsolescent or not, and in 1943 when the decision was made to standardize on the 75mm. The first decision helped delay the introduction of the 6 pdr, and the impact of the second has already been noted here. The Americans had a somewhat different problem than the British. We expected tank destroyers to do the main work of fighting German tanks while the Sherman supported the infantry and exploited breakthroughs. Our TDs were reasonably well armed from the first, but of course a TD is not a tank and can't do all the things a tank can do. It took some time for us (and especially Lesley McNair) to admit that the tank destroyer could not do the job on its own and that we were going to have to re-arm the Sherman AND develop a completely new tank (the Pershing).

I sometimes think we are a little too hard on Allied tank and gun designers. Despite mistakes and delays (see Phylo's post above) we and the British scrambled reasonably well and produced just enough tanks and TDs with good guns to do the job. By the time of OVERLORD, the British had the Firefly and the Achilles, with the Challenger and the Archer set to go. All of these had the 17 pdr, which could kill anything the Germans had. We had the 76mm Sherman, though it proved a bit disappointing, plus the M10 with the 3" gun, the M18 TD (76mm), and the M36 TD (90mm gun) about to enter service. By early 45, the Comet and the Pershing were entering service. By the end of the war in Europe, British tank troops had one-half Fireflies and some of our units were completely equipped with the 76mm Sherman. If the war had lasted 6 months longer the 75mm gun would have disappeared completely from front line service in favor of more powerful weapons. (As in fact it did as soon as the war was over.)

I should also return to Phylo's point. While our tanks were not as well armed for tank-vs-tank combat as they should have been, there wasn't much wrong with Allied anti-tank guns or anti-tank defense. On at least two occasions in Normandy (Rauray and Mortain), Allied anti-tank defenses blunted major German armored thrusts. I have been reading about the Bulge lately, and while the Germans did briefly score a breakthrough there from the first they suffered serious losses even from American infantry with mines, anti-tank guns, and bazookas, and this put the German offensive behind schedule. The tactical lesson applied to both sides: 1944 was not 1940 and the tank no longer ruled the battlefield absolutely.

 

The US Shermans that were in the independent tank battalions directly supporting infantry were very interested in larger guns as meeting a dug in enemy rarely went well for them. However the Armored Corps that were over running German forces before they could prepare and sufficient tanks to suppress the enemy with more flanking them were less so.

Then you need to remember about the Battle for France

Allies: 144 divisions[1]
13,974 guns[1]
3,383 tanks[1]
2,935 aircraft[2]
3,300,000 troops

Germany: 141 divisions[1]
7,378 guns[1]
2,445 tanks[1]
5,638 aircraft[3][4]
3,350,000 troops

Simply put you were much for likely to encounter infantry, mines, AT guns, and fausts. Which the 75mm HE was superior against.

 

your last sentence confuses me....[ sorry ]..the Armored Corps did not want heavier guns? and do you mean they had insufficient tanks?

 

The tricky part, it seems, was finding a gun that had both sufficient penetrating power against armor and a good enough HE shell for use against other targets. The 6-pdr did have an HE round, but of course it was on the light side. The 17-pdr HE round was not supposed to be very good, and I have read that apparently US crews didn't like the 76mm HE much either. I am not sharp enough technically to get all the details right, but apparently the high velocity of the 17-pdr was a problem when it came to developing a good HE round for it. No doubt others here can contribute on that point. I don't know how the Germans managed with this issue.

 

If tanks are not "meant to fight other tanks" why do current MBT mount guns with ridiculously high muzzle velocities, sophisticated AT rounds and "just decent" HE shells ?

Tanks will suffer the biggest losses when piercing the enemy's main line of resistance , or in infantry support roles where they will suffer attrition from AT weapons, but once a breakthrough is achieved their biggest enemy (besides running out of fuel) is their opponents armoured reserves, if they win that battle they can most likely win the campaign and that's what armoured forces are meant for so AT performance is critical to fulfilling the tank's main role, even though HE performance will more often come into play.

 

that's what I was thinking?? the Israelis did it ''like'' that

 

From what I've read in 44 and 45 most American tankers would have been very happy with a Sherman equipped with a 90mm gun. That would have given them a plus both against tanks and against soft targets. It was considered but the Pershing was in the works and they underestimated how long it would take to field it.

 

From http://www.ww2f.com/topic/53501-m4-sherman-gun/page-2

There's always resistance against new weapons.

The armored corps usually had sufficient tanks to quickly swamp enemy resistance with numbers and until past Normandy had never faced Tigers. Those having been sent to stop Monty's advance.

 

yes, ...isn't a 90mm HE better than a 75HE?

 

Well...apart from the fact that a tank doesn't fire HE at another tank?

HE can sometimes bear a very close look-at in terms of burster charges; they are, after all, steel pointed things with a burster charge inside....and the "shell" (sic) tamps the exploding burster charge until the expansion of gases is enough to fracture the case - resulting in a rapidly-expanding shockwave/shell fragment wave outwards...the "blast".

Sounds basic....but not all burster charges vs. thickness of shells are the same You can have small burster charges for example that result in the pressure/shockwave being more limited in extent. If Shekldrake is about he can explain it better than me.

It's the same principle as behind "iron" bombs - a 1,000lb bomb is 1,000lbs in total weight, not of burster charge! And those burster charges can sometime be a bit on the weak side. RAF "iron" bmbs on the outbreak of war, for example...hence the British having to develop "Medium" and "High Capacity" bombs that had more explosive in them compared to casing - to maximise the BLAST they could produce

 

I've linked this before but here's something concrete on the 17pdr/90mm/76mm debate.

http://forums.spacebattles.com/threads/us-firefly-17-pounder-vs-90mm-vs-76mm.285284/

http://worldoftanks.com/dcont/fb/image/tmb/comparisons_808x887.jpg

 

Certainly bigger. Late war I suspect there was a better chance of having proximaty fused rounds available as well.

But they do fire them at soft targets such as infantry and AT guns.

 

Something I've wondered about - of course if you're bombarding an area target, heavier shells will have more effect, but tanks are usually doing direct fire against point targets like AT guns or buildings, looking for a direct hit or close to it. If an HE shell explodes on or close to the target, is there much effective difference between say a 75, 88, or 90mm?

 

But they do not always hit one or very close to the target. Assuming a equally well designed HE round, bigger should be better at near the proportions of the size. But shell design is sometimes not equal. The 75mm Shernan had a better HE round than the 76...... Why has been discussed here before to no really clear conclusion.

Post WW2 the Israeli's managed to mount a 105mm main tank gun, not the US howitzer 105, in their Super Shermans. . If I remember correctly it was a French 105 mm rifle that they cut the barrel length a bit, used a slightly smaller case and added a counterweight. I do not know how it worked inside the turret.

How did such a nice article on the 76, 17 pounder and 90mm get onto spacebattles,com ???? Great link. !

 

The 75mm HE round apparently contained about 1.5 lbs of explosive while the 90mm contained 2lbs so a substantially larger blast. Fragmentation effects were highly round dependent.

 

I would think the 90mm HE would destroy/kill just as well [ if not better ] than a 75 HE..so why not use the better gun at killing tanks?