Small caliber shell impact on armors?

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The Axis WWII discussion group is hosted by Tom Cockle and is dedicated to Axis armour of the Second World War.

Small caliber shell impact on armors?

Joined: March 31st, 2004, 1:15 pm

October 10th, 2011, 1:44 pm #1

Hi!

I have some questions regarding small caliber shell, something 20mm and smaller.

How does it look like on different type of armors? Heavy, thick rolled armor plate on German tank or heavy cast texture of Russian armors. Does it chip off some paint? Does it leave some scar?
When I visited Saumur tank museum, I remember seeing some shell marks on the front plate of Sdkfz 251. I saw some similar marks on StuG III, on the rear plate I think. They all looks small, .50 cal or smaller.
I guess it would certainly chip off some zimmerit.

Another question is about the practice of firing small arm against AFV. Hollywood seems to depict spraying machine gun all over the place. What about in real life? Would an infantry squad fire everything they got in face of a Tiger I attack? Well, I only want to know if small fire arm can leave some scar on AFV, how common are these scar? Does every/ most of the tank has them?

Cheers!

Nanond

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Joined: September 27th, 2005, 12:55 pm

October 10th, 2011, 2:51 pm #2

Nanond,

Small calibre impacts will leave marks on any armour: dents, pits, gouge marks, grooves, "scars" etc. etc.
Also it will take away zimm and paint alike on the spots hit and surrounding.
effects are, naturally, also affected by the type of rounds fired. Ball may leave only very faint traces while AP leaves very visible marks.

As for small calibre fire in effective use against armour; it probably will not take out an AFV, but might very well blind it by destroying optics and reduce it's combat effectiveness by forcing the crew to stay under armour. So you can bet on it that an inf. unit faced by an armoured attack will put in a lot of fire against the attack iff there's no other course of action can be taken(evade/retreat).

greetz,

Menno.
Last edited by Menno van Os on October 10th, 2011, 2:55 pm, edited 1 time in total.
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Joined: May 13th, 2004, 7:17 pm

October 10th, 2011, 4:25 pm #3

Depends on the velocity and type of the rounds, more than the size. Also the type of armor, soft or hardened, the thickness and the angle or the impact.

A head on impact on the front of a Panther or KT and the round be deflected up. Now get a downward angle and things change. The round could penetrate or just leave a round impact crater.

The Russians wrecked havoc on the sides of German taks with their anit-tank rifles, firing a very high velocity 50 Cal sized round. This was the reason for the skirts on the sides of the German tanks.

Now the depleted Uranium penetrator darts fired by the M1's 120mm gun put the power of the 120mm gun into a very small point and is able to go through any armor put up against it. This is the theory behind the SABOT rounds.
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Joined: March 31st, 2004, 1:15 pm

October 10th, 2011, 4:44 pm #4

Hi! Jim,

Thank you for you comment:) Yes, those factors need to be considered too.

I think my question was too broad and general. Maybe better ask, how Russian 12.7 mm heavy machine gun impacts look like on Panther. or How much impact does 20 mm flak make on KV/JS tanks?

What is suggested method of depicting them on model? I usually paint some small chipping dots on the armor surface. Could it be more than just scratch? dents perhaps?

Nanond
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Joined: March 31st, 2009, 4:37 am

October 10th, 2011, 10:21 pm #5

Depends on the velocity and type of the rounds, more than the size. Also the type of armor, soft or hardened, the thickness and the angle or the impact.

A head on impact on the front of a Panther or KT and the round be deflected up. Now get a downward angle and things change. The round could penetrate or just leave a round impact crater.

The Russians wrecked havoc on the sides of German taks with their anit-tank rifles, firing a very high velocity 50 Cal sized round. This was the reason for the skirts on the sides of the German tanks.

Now the depleted Uranium penetrator darts fired by the M1's 120mm gun put the power of the 120mm gun into a very small point and is able to go through any armor put up against it. This is the theory behind the SABOT rounds.
sabot came from KE submunition, which existed at the time, or even before the russian started using PTRD. Higher muzzle velocity just meant more kinetic energy. The main concept behind the idea of sabot was a light filling that allowed gathering of energy more efficiently, and discarded during flight so all the energy would be transferred onto the smaller penetrator. Adding sabot doesn't make the penetrator go faster, nor does the penetrator accelerate after discarding the sabot.

Medium caliber today, 20mm, 25mm they can have as much as couple MJ of kinetic energy when fired at hypervelocities. and that's enough energy to move quite a bit of metal (roughly a car traveling at 200 miles/hour). How much metal get pushed away has very little to do with diameter of the penetrator (in penetration calculation the diameter is taken into count in the form of an added variable by L/D ratio), but does depend on how densely packed the armor material was. A 25mm APDS from bradley has more KE than a WWII german 50mm, it will make a bigger hole.

So vise versa, a WWII 20mm, probably had 1/4 the energy of a 37mm, which had about 1/4 of the KE of a 75mm. So a 20mm would probably make a impact crater about 1/16 the size of a normal 75mm (not a high velocity).
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Joined: June 12th, 2004, 11:07 pm

October 11th, 2011, 8:50 pm #6

Hi!

I have some questions regarding small caliber shell, something 20mm and smaller.

How does it look like on different type of armors? Heavy, thick rolled armor plate on German tank or heavy cast texture of Russian armors. Does it chip off some paint? Does it leave some scar?
When I visited Saumur tank museum, I remember seeing some shell marks on the front plate of Sdkfz 251. I saw some similar marks on StuG III, on the rear plate I think. They all looks small, .50 cal or smaller.
I guess it would certainly chip off some zimmerit.

Another question is about the practice of firing small arm against AFV. Hollywood seems to depict spraying machine gun all over the place. What about in real life? Would an infantry squad fire everything they got in face of a Tiger I attack? Well, I only want to know if small fire arm can leave some scar on AFV, how common are these scar? Does every/ most of the tank has them?

Cheers!

Nanond
I believe this damage is attributed to .50 cal damage from an aircraft - the mantlet should be a good indicator of cast surface hits, and the rolled plate glacis for smooth surface armor;
Regards, justin pockar
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Joined: June 12th, 2004, 11:07 pm

October 11th, 2011, 8:59 pm #7

Hi!

I have some questions regarding small caliber shell, something 20mm and smaller.

How does it look like on different type of armors? Heavy, thick rolled armor plate on German tank or heavy cast texture of Russian armors. Does it chip off some paint? Does it leave some scar?
When I visited Saumur tank museum, I remember seeing some shell marks on the front plate of Sdkfz 251. I saw some similar marks on StuG III, on the rear plate I think. They all looks small, .50 cal or smaller.
I guess it would certainly chip off some zimmerit.

Another question is about the practice of firing small arm against AFV. Hollywood seems to depict spraying machine gun all over the place. What about in real life? Would an infantry squad fire everything they got in face of a Tiger I attack? Well, I only want to know if small fire arm can leave some scar on AFV, how common are these scar? Does every/ most of the tank has them?

Cheers!

Nanond
same jagdpanther, close-up;


These images posted for discussion purposes only.
regards,
justin pockar
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Joined: March 19th, 2007, 1:04 pm

October 12th, 2011, 4:28 pm #8

sabot came from KE submunition, which existed at the time, or even before the russian started using PTRD. Higher muzzle velocity just meant more kinetic energy. The main concept behind the idea of sabot was a light filling that allowed gathering of energy more efficiently, and discarded during flight so all the energy would be transferred onto the smaller penetrator. Adding sabot doesn't make the penetrator go faster, nor does the penetrator accelerate after discarding the sabot.

Medium caliber today, 20mm, 25mm they can have as much as couple MJ of kinetic energy when fired at hypervelocities. and that's enough energy to move quite a bit of metal (roughly a car traveling at 200 miles/hour). How much metal get pushed away has very little to do with diameter of the penetrator (in penetration calculation the diameter is taken into count in the form of an added variable by L/D ratio), but does depend on how densely packed the armor material was. A 25mm APDS from bradley has more KE than a WWII german 50mm, it will make a bigger hole.

So vise versa, a WWII 20mm, probably had 1/4 the energy of a 37mm, which had about 1/4 of the KE of a 75mm. So a 20mm would probably make a impact crater about 1/16 the size of a normal 75mm (not a high velocity).
drag beacause of small frontal area and possibly also length/frontal area, and also greater inertia (as compared to a composite/rigid round or a traditional penetrator, won't it?
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Joined: March 31st, 2004, 1:15 pm

October 13th, 2011, 10:25 am #9

same jagdpanther, close-up;


These images posted for discussion purposes only.
regards,
justin pockar
Thank you for the pic Justin.

Nanond
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Joined: March 31st, 2009, 4:37 am

October 14th, 2011, 10:58 pm #10

drag beacause of small frontal area and possibly also length/frontal area, and also greater inertia (as compared to a composite/rigid round or a traditional penetrator, won't it?
and larger caliber always take more losses.
also the faster the more losses. More than 50m/s per 100 meters for modern AT rounds. This has a lot to do with the actual sabot design of course. The russian belt shaped sabots reduces velocity at almost twice the rate.

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