Reply #46: One problem was the gunpowder.

[formercia]

The original M-16 round used an extruded single-base propellant but the powers that be decided that using a double-base ball powder would increase the muzzle velocity a couple of hundred FPS. They also specified the addition of extra Graphite coating on the powder grains for lubrication. The Graphite is what was fouling the gas tube and causing cyclic malfunctions. Some rounds wouldn't even fire from the Graphite that would settle in the case and block the primer opening.

The AK was more reliable in part because the Soviets used chrome-lined barrels to prevent corrosion. In tropical climates, an electrolysis reaction between the brass cartridge case and the steel chamber wall would cause corrosion and subsequent jamming.