15mm BESA Armour Piercing & Armour Piercing Tracer

The armour piercing round was "Cartridge S.A. Armour Piercing 15mm W Mark I" if loaded with cordite or Mark Iz when loaded nitro-cellulose. The Mark Iz round was approved in June 1940 and shown in LoC Paragraph B.3738 dated August 1940.The Design was DD/L/10003 (later DD/L/14011) and the bullet was boat tailed with a gilding metal envelope with a lead/antimony tip filler and hard steel core. It had two narrow driving bands formed in the envelope. Bullet weight was 1160 grains and the propellant charge was 325 grains of Cordite for the W Mark I and 370 grains of nitro-cellulose for the W Mark Iz.Velocity at 90 feet was 2,900 feet per second at a maximum mean pressure of 22 tsi and penetration was seven out of ten shots must penetrate 27mm armour plate at 100 yards.The headstamp should include the code "WI" or "WIZ" and the primer annulus was green.The marking of 15mm BESA rounds however did not always strictly follow specification and early rounds, whatever the loading, were headstamped with maker and date and "15mmWZ". Also some armour piercing rounds will be found with a green tip.The W Mark I and Iz was declared obsolete in January 1945.Illustrated is an early 15mm BESA Armour Piercing round with unusual green tip. Headstamp is "K 40 15mmWZ"Armour piercing W Mark Iz stamped (i) "WIZ" and (r) "WZ"