Ball, M55 : A generic 115-grain boat-tailed, open-tipped projectile much like the Mk 262 . White cap. Cartridge, 7mm Ball, Tracer, M55A1 : A generic tracer conversion. White cap with one red band on the case. Cartridge, 7mm Ball, Tracer, M55A2 : Alternate-color tracer to warn of an imminent magazine change.