Copyright International Ammunition Association, 2008. All rights reserved.
Cartridge of the Month March 2008

37 x 264mmB German APCR Hartkern
Specimen and photos courtesy of Fred Butt
(References variously call this 37 x 263B, 37 x 264B or 37 x 265B).


Armor piercing (AP) ammunition for medium caliber guns began with solid projectiles of hard steel.


Later, a much harder penetrator was placed in the projectile, often with the remainder of the projectile made of a lighter material (such as aluminum) for greater velocity. These were called "Armor Piercing, Composite, Rigid" or APCR


Eventually it was decided that the maximum penetrtion would be achieved if the surrounding body needed to guide it during firing in the barrel could be removed from the penetrator leaving the pentrator travelling at high velocity without the added weight or drag of the body. This resulted in the APDS (Armor Piercing Discarding Sabot) concept.




The cartridge shown here is the German version of the APCR hardened core (hartkern) concept. These were used with the Rheinmetall-Borsig BK 3.7 which was derived from the FlaK 18 anti-aircraft gun. These guns were used in an anti-bomber role and especially on the Eastern Front in an anti-tank role. They were often mounted in the Ju-87G Stuka, and also the Ju-88P-2 and the Hs-129B-2/R3. The airborne anti-tank role was so important that it was theo only authorized use of the 3.7 cm hartkern ammuntion after the summer of 1944


The hardened core penetrator would penetrate 70mm of armor at a 60 degree angle at 100 meters, or 140mm of armor at a 90 degree angle.


Note the cloth packet in the case with the propelling charge. [Was this for anti-flash or ignition purposes?]

Note the propelling charge of cordite type powder.

Tony Williams, Rapid Fire, p. 13, 169

Copyright 2008 by the International Ammunition Association, Inc. All rights reserved.

[Close this page to return to the IAA Cartridge of the Month Index]

Return to IAA main page

  Revised 5 March 2008