Although the M113 (Armored Personnel Carrier) was initially designed to carry a full 10 man rifle squad in addition to the two-man crew in its role as a valuable transport in a variety of terrain; lessons learned in Vietnam soon evolved into the M113(ACAV) and the ""Cavalry Fighting Doctrine"" to fight directly from the track on the move and not to dismount the infantry unless in extreme circumstances. Now the track became a mobile fire platform and stowage of enormous quantities of ammo and other equipment considerably reduced the internal troop carrying capacity.
A normal crew for the ACAV was a driver, track commander, two gunners, and two loaders (one of whom would also be armed with an M-79 40mm grenade launcher. Protected by between 12 and 38 millimeters of armor, a .50 caliber Browning machine gun mounted in an armored gun shield/turret combination (manned by the TC) and two 7.62 mm M60 machine guns (manned by the two gunners), mounted one either side of the rear hatch and fitted with protective gun shields. Typical ammo load could consist of 3,500 rounds of M2 .50 caliber, 8,500 rounds of 7.62mm, 5,000 rounds of M-16 ammo, and 150 40mm grenades. The track traveled at speeds of over 40 miles per hour.