Yards

CClsrrMJt R: i 3W

The Colt M4 favored high-speed, hunting-type .22 LR ammunition.

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CClsrrMJt R: i 3W

The Colt M4 favored high-speed, hunting-type .22 LR ammunition.

sharing 80 percent of its parts with Canada's version of the M16A2, the C7.

Conversion units are handy, but they're susceptible to two problems. First, they are conversions, compromises, not original equipment. The firing system assemblies and rimfire magazines have to be built with tolerances so it will work in all makes of uppers and lowers. Insuring the rimmed, outside lubricated, .22 LR round will feed, chamber, fire, extract and eject in semi-automatic mode is hard enough without building any compromises into the system.

The real killer to the conversion unit solution though has been the change in the rifling twist incorporated into current M16 and AR-15 models. The original 5.56mm round, the M193, featured a 55-grain projectile stabilized in a standard 1:12" twist barrel. In a 1:12" twist barrel, the .22 LR round did fine. When the 62-grain SS109 round was adopted and the rate of twist was increased to 1:7", the soft, lead bullet of the .22 LR proved incompatible. In the faster rate-of-twist, the bullet was highly deformed, leaded the barrel excessively and was inaccurate.

Since then, the world has been waiting for a Colt M4/M16 clone built specifically for the .22 LR. It's here.

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