Like many automatic and semi-automatic weapons the M16 utilizes pressure from the propellant gases in the barrel to cycle the bolt of the firearm.
This is not the case in the M16 design in which gases are tapped off the barrel near the muzzle and flow through a tube to directly impinge on the bolt to initiate the auto loading cycle.
In a standard issue M16, the gas tube is roughly 16 inches (410 mm) long to produce an automatic (cyclic) rate of fire of approximately 650 rounds per minute.
M16Ks make use of the stainless steel twin-tube La France gas system, which greatly increases reliability using the short barrel.
[citation needed] The later M16K-45 variant was produced using proprietary upper and lower receivers designed by Timothy F. La France specifically for the .45 ACP round.
Fully automatic and semi-automatic versions of the M16K-45 may be obtained from North American Integrated Technologies (NAIT) in Texas, which provided the funding for development, testing and production of the M16K-45 variant.