.50 inch Browning Incendiary
Although adopted for service British authorities were unhappy with the American Incendiary M1, considering it not to be bore safe due to the incendiary composition being pinched between the steel sleeve and the envelope. The development of a British incendiary was considered a high priority.
The M1 incendiary had been developed by Remington and limited numbers were supplied for the RAF under contract in 1940.
Incendiary B Mark Iz
"Cartridge S.A. Incendiary .50 inch Browning B Mark Iz" should be the British title for the American M1 incendiary round, since this would follow the pattern of other .50 inch Browning loads. However it appears that this was not the case, and the B Mark Iz was a British design based on the successful .303 inch B Mark VIIz. It was very short lived and no confirmed specimens are known.
The case was a British manufactured .50 inch Browning fitted with a Berdan primer with a blue primer annulus. The headstamp may have been the early ROF Spennymoor "/|\ /|\ 1941 .50"
The bullet had a gilding metal envelope containing a steel sleeve within a thin lead outer sleeve. The incendiary composition was contained within the steel sleeve and the tip of the bullet in a similar manner to the .303 inch B Mark VII incendiary.. The tip of the bullet was blue and the weight was 690 grains.
Incendiary B Mark IIz
"Cartridge S.A. Incendiary .50 inch Browning B Mark IIz" was approved to design DD/L/11847 in late 1941.
The case was a British manufactured .50 inch Browning fitted with a Berdan primer with a blue primer annulus. The headstamp was typically "SR 1942 .50", but some rounds were loaded in Britain in Canadian cases headstamped "DI 42".
The bullet was flat based with a gilding metal envelope containing a steel sleeve within a thin lead outer sleeve. The incendiary composition was contained within the steel sleeve and the tip of the bullet in a similar manner to the .303 inch B Mark VII incendiary.. The tip of the bullet in early production was pierced with a small solder filled hole, but this was omitted in later production from May 1943. Bullet weight was 710 grains and the tip was coloured blue.
The incendiary composition was 36 grains of SR 365 with 2 grains of QF composition in the nose.
Early B Mark IIz showing solder filled hole in nose.