text: Explosive, T99: Development of a cartridge that contained a small explosive charge that more effectively marked its impact. Often referred to as an "observation explosive" cartridge, it was meant to designate line-of-sight targets for cannon. The T99 was never adopted.
  Frangible, T44/M22 (April 1945): The bullet disintegrates upon striking a hard or armored target, leaving a pencil-like mark to indicate a hit during bomber aerial gunnery practice. The bullet is identified by a green tip over a white ring.
  Gallery practice M1919 / Guard M1: A reduced-charge Ball cartridge with a 140-grain wax-coated lead round-nosed bullet used for target shooting at indoor facilities or near built-up areas. It was later renamed the Guard M1 in 1933 and was used for guard and sentry duty at defense plants and military installations during World War II.
  Guard M1906 (1907–1918): A reduced-charge ball cartridge with a 150-grain FMJ pointed-nose bullet used for guard and sentry duty in built-up areas. The cartridge was originally marked with six cannelures in the middle, but this weakened the case and caused it to burst in a dirty rifle. It was later marked by six dents or flutes on the shoulder of the cartridge. Although production stopped in 1918, there were plenty of stocks of the oddball round left until the 1920s.