12.7 mm cartridge with B-32 armor-piercing incendiary bullet The 12.7mm 57-BZ-542 cartridge with B-32 armor-piercing incendiary bullet is used against enemy personnel, soft-skinned ground and low-flying vehicles when fired from 12.7mm machine guns, except the YakB-12.7mm machine gun, at temperatures from -50 to +50 °C.