This gun is a further iteration on the ultra short 5.56mm M16K carbine made by La France. The M16K-45 uses proprietary upper and lower assemblies resized for the smaller cartridge, as well as using La France’s patented adjustable twin gas tube system, designed for higher reliability on short barrel guns. It uses M1 Thompson stick magazines.
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It’s firing .45 ACP (Automatic Colt Pistol), a pistol cartridge, out of a 7.5 inch barrel. It is stabilized. For comparison the standard size 1911 has a 5 inch barrel, the Kriss Vector SMG has either 5.5 or 6.5 inch barrel (depending on model), and the M3 Grease gun has an 8 inch barrel.