Army APC -Vietnam era.
The basic M113 armored personnel carrier can be fitted with a number of weapon systems. The most common weapon fit is a single .50 caliber M2 machine gun. However, the mount can also be fitted with a 40 mm Mk 19 automatic grenade launcher. A number of anti-tank weapons could be fitted to the standard variant: the U.S. Army developed kits that allowed the M47 Dragon and BGM-71 TOW anti-tank missile systems to be mounted. In the case of the M47, the system mated to the existing machine gun mount, without having to remove the machine gun. This allowed the commander to use both weapons. A large array of turrets and fixed mounts are available to mount high explosive cannon ranging from 20 mm to 105 mm on to the M113 series, making them function as assault guns and fire support; while in many cases still having room inside to carry dismounted infantry or cavalry scouts.
The M113 is built of 5083 aircraft-quality aluminum alloy, which gives it some of the same strength as steel at a slightly reduced weight, as the greater thickness allows structural stiffness. The M113A3 was designed to provide protection against 7.62mm threat, and this proved not to be enough when tested in combat.
In comparison, modern APCs like the Stryker have an all-around 7.62mm armor-piercing protection, plus 14.5 mm protection on the front, sides, and rear. Also protection against antipersonnel mines through the vehicle floor is installed.