PANZER SURVIVAL IN FRANCE

[rexford]

Shatter gap is documented in U.S. tests on projectile nose hardness effects, where harder noses penetrated more armor. German ammo was harder than others, and in U.S. tests 75mm Pak round out-penetrated U.S. 75mm from Sherman at same velocity and weight.

U.S. penetration data from Naval sources also documents shatter gap failure. It is called a shatter gap because the round penetrates, then it fails, then it penetrates again, as velocity increases.

The definition of penetration data also works to panzer benefit.

When penetration equals armor resistance, half the hits succeed and half fail. This is U.S. Navy Ballistic Limit.

When 75mm APCBC ammo from Sherman exactly matches driver plate on PzKpfw IVH, 50% survival rate. To obtain 100% penetration success rounds have to exceed armor resistance by at least 10%, which is in middle of shatter gap region.

British put armor piercing caps on their solid shot to reduce shatter gap tendencies, which they were forced to acknowledge in North Africa. British tests with best quality ammo showed that armor piercing caps reduced shatter gap effect to almost zero.

However, British firing tests against captured Tiger with various of their APCBC resulted in shatter failures where penetration should have occurred.