Walther Colt M4 is a line of semi-auto rifles, replicas of the famous M-16 machine gun. The Colt M4 series by Walther is manufactured under the Colt license and is the only genuine Colt tactical rimfire replica in the world. The Walther Colt M4 Carbine is available in a 22 LR caliber, with a 16.2-inch barrel, adjustable sights, and a 30-round magazine. The overall length of the carbine ranges from 31.1 to 34.4 inches.