The 12.7×99mm, often referred to as .50 caliber cartridges are NATO standard ammunition, used primarily in heavy machine guns and anti-materiel rifles in all branches of the U.S. military. The family of .50 caliber ammunition consists of ball, tracer, armor piercing, incendiary and dummy cartridges, among others.
The M8 API is used by M2 machine gun and the M107 Long Range Sniper Rifle. The cartridge combines the functions of the M2 armor piercing bullet and the incendiary bullet, and is used against flammable targets and light-armored or unarmored targets, concrete shelters, and similar bullet-resisting targets.
The M17 Tracer is used by M2 machine gun and the M107 Long Range Sniper Rifle. The cartridge tracer is intended to permit visible observation of the bullets in-flight path or trajectory to the point of impact. It is identified by a brown bullet tip.
The M20 API-T is used by the M2 machine gun and the M107 Long Range Sniper Rifle. It is a tracer cartridge, it's dim at near ranges, but increases to bright as it moves further from the gun. Its characteristics and usage is similar to that of the M8 API cartridge.
The M23 Incendiary is used by the M2 machine guns. The cartridge is used against flammable targets. It is capable of initiating combustion of flammable materials upon target impact at 175 yards (160 m). The cartridge is identified by a blue bullet tip with a light blue ring to the rear of the blue tip.
Ther M903 SLAP cartridge is used by M2HB machine gun. It is used in combat against light armored targets and helicopters. The M903 offers the capability to defeat these targets at ranges two to three times that of previously available ammunition. The cartridge consists of a heavy metal (tungsten) penetrator that is sabot-launched at a much higher velocity than standard rounds.
The M962 SLAP-T is used by the M2HB machine gun against light armored vehicles and aircraft with the additional tracer feature. The cartridge consists of a tungsten alloy penetrator of the same mass as the M903 Saboted Light Armor Penetrator.
The MK 211 is used by the M2 machine gun and the M107 Long Range Sniper Rifle against light armored vehicles and aircraft. This cartridge provides improved penetration performance against enemy personnel and light armor vehicles.