Pershing Mantlet Resistance

[rexford]

A report entitled THE VULNERABILITY OF ARMORED VEHICLES TO BALLISTIC ATTACK, from Aberdeen Proving Grounds, has been reviewed and this post will deal with tests against Pershing front armor. The report is dated September 1950.

Page 107 of the report lists the protection ballistic limits against the Pershing glacis and mantlet when attacked by 90mm M82 APCBC. The velocity for 50% penetration success is 2737 fps against the glacis and 1652 fps versus the mantlet center.

The 50% velocities relate to effective vertical thicknesses of 168mm on the glacis and only 73mm for the mantlet. Using the slope effects and cast armor modifiers in our book, the effective resistances are estimated at 176mm glacis and 108mm mantlet.

The glacis resistance from the firing tests is within 5% of the figure we calculated, but the mantlet resistance is -32% lower.

The remarkable aspect of the ballistic test findings is that a 112mm cast mantlet offered 73mm of rolled armor resistance, which suggests potential problems with the casting. While the report recognizes an unbalance in the mantlet and glacis resistance, the magnitude of the difference is not identified or discussed.

While American quality control was improved during October 1943, the low ballistic resistance of the Pershing mantlet raises a number of questions regarding casting quality.

When 75mm M72 strikes 3" of U.S. cast armor (Thickness/Diameter=0.98), the casting presented 89.4% of the resistance of 3" of rolled armor. When 90mm M82 strikes 112mm of Pershing mantlet (T/D=1.24), the equivalency is 68%. Based on T/D ratio, the Pershing mantlet thickness multiplier should be over 90%.

[ 12-16-2001: Message edited by: rexford ]</p>

[Jarmo]

Umm.. mantlet. What about the rest of the turret?

Anyway, if this finding is reliable, then CM would have too high values for Pershing?

Interesting read.

[gunnergoz]

Perhaps this tells us something about why US tank turrets had increasingly smaller mantlets in the coming years...M47, M48, M60 and M60A1 all had cast mantlets but the shapes were smaller and presented less frontal target area than the broad expanse of the M26/M46 series mantlet. Were we learning an important lesson? I would venture a guess that we were. It's possible that smaller castings could be better QA'd during production to insure the correct armor value was retained. Although the US stuck to large, complex castings in the hull, it was always anticpated that more hits would go to the turret face - and mantlet - if tankers stayed hull down and faced front to the enemy, i.e. the classic defensive posture that US Army planners envisioned for their tanks in use against the Red Hordes.

[rexford]

One of the responses to my post on the i-mdb.news (Saumur Intranets service), regarding those ballistic tests against Pershing front armor, stated that Russian tests against the cast mantlets on M46, M48 and M60 resulted in the conclusion that American mantlet castings were significantly less resistant than the rolled glacis plate on T55.

This is the post by Vasiliy Fofanov in response to my statements:

"

> While American quality control was improved during October 1943, the low ballistic resistance of the Pershing mantlet raises a number of questions regarding casting quality.

This property of US cast armor was well known in USSR and has been found to also be the case in M46 and M48 following trials of these vehicles. I did not see the M60 trial report, but I heard the same was discovered.

> When 75mm M72 strikes 3" of U.S. cast armor (Thickness/Diameter=0.98), the casting presented 89.4% of the resistance of 3" of rolled armor. When 90mm M82 strikes 112mm of Pershing mantlet (T/D=1.24), the equivalency is 68%. Based on T/D ratio, the Pershing mantlet thickness multiplier should be over 90%.

According to the reports I mentioned, front cast armor elements on M26 and M46 resisted on average by a one third worse than the reference T-55

glacis armor plate (i.e. RHA), using 100mm ATG (BS-3 I presume). This seems in accordance with what is reported here.

Best regards,

Vasiliy"

Good point about the cast mantlets getting smaller and smaller.

The Pershing glacis in the American test report did about as well as one would expect from tests, and provided about 94% of the resistance a rolled plate would offer. Not bad, and much better than the mantlet. Maybe all those holes in the mantlet did something unexpected on hits from the openings.

The booklet Hammer of God, on the 1973 mid-east war, had some photo's which purported to show that T62 cast turret armor would totally fail on hits that would be unable to penetrate, based on penetration-vs-thickness/angle considerations.

What is it with cast armor? Although Tiger and Panther cast mantlets were famous for their ability to take tons of punishment and resist with close to rolled armor capability.

[Ari Maenpaa]

Interesting read once again Rexford, thanks.

After reading your numerous and informative posts about the features of different tank armors I'm getting the feeling that not one tank had 100% quality armor during the war. Every type of armor had flaws of it's own.

Ari

[Brian]

<blockquote>quote:</font><hr>Originally posted by rexford:

What is it with cast armor? Although Tiger and Panther cast mantlets were famous for their ability to take tons of punishment and resist with close to rolled armor capability.<hr></blockquote>

I'd have assumed that its not only about the way the armour is cast but also the shape its cast in.

I must admit that I've always understood that with casting, its a great deal harder to get the cast to cool uniformly, particularly with larger pieces, with the consequent problem that the metal has areas which are not as strong as others, in the cast. Rolled armour tends to be more uniform in quality, over the total surface of the plate (although your recent post on Panther glacis tends to cast doubts on that presumption IMO).

Perhaps the point is, that whilst with casting you can get a better shape, you have to trade that off against problems with ensuring adequate hardness throughout the whole cast.

As someone noted, the US moved to smaller and smaller cast mantlets. The UK moved to first cast and then plate mantlets and eventually eliminating them completely in the Chieftain, while the Russians also moved to smaller castings over the years.