Sherman Armor and Penetration Topics

[rexford]

This post and following additions contain some recent work regarding the capability and armor resistance of Sherman tanks and U.S. armor piercing weapons and ammo. The material summarizes (and in some cases belabors) the data in our book.

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Using the curves and procedures in our book on WW II BALLISTICS, we analyzed the effective resistance of the M34A1 gun mount against 75mm APCBC using modifiers for slope effect, cast armor deficiency to rolled plate, flaws edge effects and spaced armor.

The following is a breakdown of the armor resistances (0° effective) based on random distribution of hits against the gun mount on 56° glacis Shermans and Fireflies:

8% hit 45mm effective resistance

6% hit 65mm

22% hit 75mm

25% hit 85mm

18% hit 95mm

6% hit 105mm

4% hit 115mm

3% hit 125mm

4% hit 145mm

1% hit 155mm

3% hit 165mm

The average armor resistance is about 89mm.

Against 75mm armed Shermans with 47° glacis plates (unflawed armor), armor resistance would be about 5% higher.

While some of the figures suggest very good resistance on some hits, the spaced nature of the two shields results in a phenomenom called keying, where the outer shield is fully penetrated and the round sticks in the inner shield, which freezes the gun elevation system.

Our calculations indicate that almost every 75mm and 88mm projectile hit on the M34A1 gun mount will fully penetrate the outer shield, which creates a large number of situations where hits that should be defeated are able to create some damage to the gun system.

The low armor resistance figures are due in many cases to openings in the inner shield and edge effect considerations.

[ 09-14-2001: Message edited by: rexford ]

[rexford]

Using the data and procedures in our book on WW II BALLISTICS, we prepared front hull resistance stats for the different Sherman models (and Pershing), based on cast armor deficiency to rolled plate and assumption that tanks built prior to October 1943 had flawed armor (that date marks the required use of improved quality control and heat treatment processes in U.S. armor manufacturing). Resistance is keyed to 75mm APCBC hits and would be somewhat lower on 88mm APCBC hits:

M4, M4A2, M4A3, M4A4 (56° glacis)

104mm for rolled glacis plates

100mm for cast glacis plates

100mm for upper nose

M4A1 Early

84mm to 92mm glacis

72mm driver and bow MG hood areas

152mm at glacis outer edges

100mm upper nose

M4A1(76)W

88mm to 100mm glacis

76mm driver hood

100mm bow MG hood

164mm at glacis outer edges

M4A3E8, M4A3(75)W, M4A3(76)W

116mm glacis

108mm upper nose

PERSHING

104mm upper glacis center (20° slope)

184mm glacis

160mm nose

German battle reports indicated that 75L48 on PzKpfw IVH and StuG IIIG could not penetrate 47° glacis armor at 1000 meters. Actual range would be much less.

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By way of comparison,

PANTHER

220mm unflawed Glacis

208mm flawed glacis

156mm nose

TIGER E

104mm driver plate

284mm glacis

116mm nose

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Interesting point is that Shermans with 47° glacis present greater resistance to 75mm hits than Tiger E.

Barring a critical hit (round strikes bow machine gun ball, weld lines at glacis/nose intersection or armor edges), 17 pounder APCBC will not penetrate Panther glacis armor based on computed armor figures. This is consistent with actual firing tests conducted by British and American forces.

Interesting result from U.S. tests at Isigny France during August 1944 is that 17 pounder APCBC won't penetrate Panther glacis at 200 yards, but it may crack brittle armor. Once Panther glacis is cracked, edge effects lower resistance to less than 70% of full effect, and 17 pounder APCBC hits near or on a crack could and did penetrate.

[rexford]

While U.S. HVAP boosted penetration of 76mm and 90mm guns against near vertical armor, tungsten rounds have much higher slope effects which decreased HVAP performance against many panzers.

HVAP Penetration at 100m, 500m and 1000m:

76mm: 239, 208, 175

90mm: 306, 278, 246

Panzer glacis and front superstructure resistance to HVAP hits is computed below:

Hetzer (60mm at 60°): 263mm at 0°

Panther (85mm at 55°): 289mm at 0°

Tiger II (150mm at 50°): 413mm at 0°

JgPz IV (60mm at 50°): 165mm at 0°

JgPzIV (80mm at 50°): 220mm at 0°

In comparison, Hetzer 60mm at 60° armor resists 90m APCBC hits like a 165mm thick vertical plate.

[rexford]

During WW II, German tank effectiveness was due in large part to the superior effectiveness of the ammunition, which is related to nose hardness considerations.

British tests against homogeneous armor at 610 m/s impact velocity, which are documented in Miles Krogfus' AFV News article, resulted in:

102mm penetration for German 75mm APCBC

90mm penetration for U.S. 76mm APCBC

75mm penetration for Russian 76mm APBC

U.S. penetration tests for Sherman 75mm indicate 89mm penetration at 610 m/s.

Based on the above figure at 610 m/s, the Panther 75mm penetration is estimated at 188mm at 935 m/s and 0m range (DeMarre equation extrapolation). Actual U.S. tests with Panther 75mm APCBC obtained 190mm penetration at 0m and 935 m/s impact.

German projectile nose hardness advantage over U.S. APCBC, 61 to 54.5 Rockwell C Hardness, also assured that German hits were outside "shatter gap" region.

During U.S. tests with 76mm APCBC, hits that overpenetrated armor resistance by 5% to 25% would FAIL due to shatter when results exceeded certain velocity and armor thickness figures. It turns out that low nose hardness results in excessive energy absorption when round overpenetrates armor, and nose may crack and break-up.

[rexford]

German use of face-hardened armor on panzers through October 1944 had a significant impact on the vulnerability of tanks to Allied APCBC projectiles.

Panther A carried face-hardened side hull plates, and PzKpfw IVH and StuG IIIG used face-hardened frontal armor.

While Sherman 75mm APCBC is often maligned due to 81mm homogeneous penetration at 500m, which severely limits effectiveness against the ultimate Sherman nemesis, Tiger E, that round could defeat 95mm of face-hardened (FH) plate at 500m.

Against a Panther on a flank hull shot, the ability to penetrate 95mm effective armor (FH) at 500m allows a much greater arc from armor facing for effective 75mm Sherman shots.

The effective range of 75mm APCBC against the front hull of PzKpfw IVH and StuG IIIG also increases greatly due to FH armor use.

German use of face-hardened armor till late in the war was probably predicated on Russian use of uncapped rounds (no armor piercing cap), which lessened effectiveness against the very hard surface layer on FH armor.

[rexford]

The British tests conducted at 610 m/s to compare projectile penetration resulted in )going by memory here and it is 4am, so please excuse small deviations from actual):

17 pounder APCBC 109mm

German 75mm APCBC 101mm

U.S. 76mm APCBC 90mm

Russian 76.2mm APBC 75mm

Miles Krogfus published test results in AFV News on AP performance during WW II.

17 pounder APCBC outpenetrates U.S. 76mm APCBC by a large margin, but 17 pounder has some advantages, it is solid shot and weights more than U.S. 76mm APCBC.

Having an HE filler generally decreases penetration by about 10% or so, based on our studies. And 17 pounder outweighs U.S. 76mm by 17 to 15.44 pounds. If 17 pounder round weighted 15.44 pounds and had an HE filler the penetration at 610 m/s would decrease to:

109 x (15.44/17)^.7143 x (.90), or about 92mm.

This shows that British APCBC and American APCBC had about the same penetration characteristics when weight and HE filler differences were sorted out. Analysis of 2, 6 and 17 pounder AP penetration and comparison with U.S. AP shows similar results, 2 pounder and 6 pounder AP penetrate with about the same "K" factor.

U.S. curves for 57mm solid shot AP result in similar penetration figures as British 6 pounder AP, and when we used the U.S. 57mm AP penetration against face-hardened armor to predict 6 pounder AP performance during actual tests against German panzers, the 57mm AP data matched the penetration ranges.

So German APCBC outpenetrates British APCBC by about the same margin as U.S. APCBC.

Regarding nose hardness characteristics of British APCBC, tests showed that 6 pounder APCBC would shatter and fail when it hit less face-hardened thickness than it could penetrate on half the hits at a given velocity, which is "shatter gap".

In North Africa, 2 pounder AP hits on panzers would fail at close range and penetrate further out, or would have a gap in the penetration range (defeat armor to 600 yards, fail from 600 to 900 yards, and then penetrate again out to 1200 yards). When rounds with nose hardnesses within a certain range overpenetrate armor by certain ranges, as armor is thrown out of the way at faster rates the nose pressure builds and the nose absorbs energy. When energy absorption exceeds certain levels the projectile nose shatters and hits fail.

The British thought that putting armor piercing caps on AP rounds would prevent shatter gap, but test results suggest that it didn't. U.S. 76mm APCBC test results follow against 3" armor at 30°:

Impact at 1954 fps, plate bulge

2065 fps, complete penetration

2073 fps, base of round sticks in plate, rest of round passes through

2160 fps, projectile sticks in plate

2205 fps, projectile splits in two and fails to pass through armor

2376 fps, projectile breaks up and fails to pass through plate

More is not always better when it comes to penetrating armor.

Actual tests of 6 pounder AP against Tiger side armor in North Africa showed shatter gap failure when the penetration exceeded armor resistance within certain ranges. 6 pounder AP knocked out some Tigers in the initial combat in Africa, if the range had been shorter the hits may have failed, which is contrary to what one would expect.

British 6 pounder APCBC would penetrate about 76mm of homogeneous armor at 610 m/s, U.S. 57mm APCBC penetration at that velocity is 70mm.

Analysis also suggests that British and American penetration test plate had about the same resistance, and good quality armor from both countries was similar and about the same as good quality German armor.

It is also important to note that tungsten rounds will fail against armor that is well below the listed penetration if the impact velocity and impact angle are within certain limits. British lab tests predicted certain results, and tests of APDS against Tiger armor showed that tungsten shatter gap occurred. Just because APDS penetrates alot of armor doesn't mean it won't fail against relatively thin armor (compared to penetration figure).

U.S. HVAP tungsten rounds generally strike at velocities where shatter gap is less of a problem, the high velocity of APDS creates more chances for shatter failure.

[rexford]

6 pdr APCBC penetration stats against homogeneous and face-hardened armor at 100, 500 and 1000 meter range:

2600 fps muzzle velocity L45 gun:

107, 96, 84 homogeneous

112, 102, 91 face-hardened

2725 fps muzzle velocity L52 gun:

115, 103, 90 homogeneous

119, 109, 97 face-hardened

6 pdr AP ammo penetration:

2700 fps muzzle velocity L45 gun:

117, 97, 77 homogeneous

93, 72, 53 face-hardened

2830 fps muzzle velocity L45 gun:

128, 105, 83 homogeneous

100, 78, 57 face-hardened

2950 fps muzzle velocity L52 gun:

135, 112, 89 homogeneous

104, 82, 61 face-hardened

[Captain Wacky]

lol! :eek: what a one sided topic! 6 gigantor posts and their all yours!

[rexford]

But wait till I start to argue with myself, even USERNAME won't want to get in the middle.

[Hanns]

BTS, fix or do somefink!

[Username]

Rexford is in complete agreement with himself and wins his own arguments.

[rexford]

I didn't say fix or do something, and I won't be able to pin myself down on any points either.

But it is refreshing to win an argument and to have USERNAME agree that I was correct, even if I was also wrong.

My plan from the beginning.

Sneaky, huh?