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The 7.92mm BESA was originally intended to be used by tanks against infantry, and so no requirement for armour piercing ammunition was envisaged. However, experience in France in 1940 revealed a need for anti-aircraft defence against dive bombers and so a demand was made in July 1940 for an armour piercing round.
ICI Kynoch were approached as it was hoped they already had a design available and they offered to supply 500 rounds to their design BK 141/189 This had a 178 grain bullet with a GMCS or CNCS envelope and no cannelure. Trials were successful and the W mark Iz was approved based on the Kynoch design.
Armour Piercing W Mark Iz
"Cartridge S.A. Armour-Piercing 7.92mm W Mark Iz" was approved to design DD/L/11806 in March 1941 and shown in Lists of Changes Paragraph B.5544 in January 1942. This entry was only for record though, as the W Mark Iz had been declared obsolescent in November 1941.
Very few of the W Mark Iz were manufactured and it was only made by Kynoch at their K2 Standish satellite factory.
The case was as for the Ball Mark Iz with a green primer annulus. The headstamp included the code "WIZ".
The bullet was boat tailed with either a CNCS or a GMCS envelope to the same profile as the Ball Mark Iz bullet. The core was of hardened steel and three types were approved, tungsten/ chromium, chromium/ molybdenum or chromium/ vanadium. the sleeve and tip were of 98/2 lead/antimony. Bullet weight was 178 grains.
The propellant was 45 grains of nitrocellulose and the observed velocity at 90 feet was 2,580 fps +- 40. Pressure was 21 tsi maximum.
Penetration was 70% of shots to penetrate 11mm armour plate at 100 yards at normal angle of attack.
Greek W Mark Iz
In addition to the WIz manufactured in the UK, some Greek armour piercing rounds were purchased in 1940 along with the ball rounds described here. These had the same "IZ" headstamp as the ball rounds but with a green annulus, so to clarify that these were actually AP rounds an additional "W" was stamped in front of the "IZ" in the headstamp.
Like the Ball Mark Iz, the W Mark Iz was found to be inaccurate in worn barrels and so after a brief service life was replaced by a new round, the W mark IIz.
Armour Piercing W Mark IIz
"Cartridge S.A. Armour-Piercing 7.92mm W Mark IIz" was approved to design DD/L/12605 in September 1941 and shown in Lists of Changes Paragraph B.5544 in January 1942.
The case was as for the Ball Mark Iz but with a green primer annulus. The headstamp included the code "WIIZ" or after 1944 "W2Z"
The bullet was boat tailed with on cannelure and either a CNCS or a GMCS envelope. Weight was 178 grains. The construction was the same as the W Mark Iz and the same three steels were approved. The bullet ogive matched that of the Ball Mark IIz.
Propellant, ballistics and penetration proof were the same as the W Mark Iz.
Typical belt mix for 7.92mm BESA rounds.
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