Colt 901 Modular Carbine Shoots Both .308 Win and .223 Rem
Colt Manufacturing Company (“Colt”) has finally released T&E versions of the long-promised Colt 901 “Modular Carbine” first revealed in 2011. This rifle shoots both .223 Rem and .308 Win cartridges using the SAME LOWER with different uppers. The Colt accomplishes this task by using a unique magwell insert, along with different mags and buffer assemblies. The 901 is very different than other AR variants which squeeze a short .30-caliber cartridge, such as the .300 AAC BLK, into a .223-length AR magazine. The Colt 901 shoots regular .308 Winchester cartridges, from .308-Win sized magazines. The key is the proprietary magwell insert, which allows standard 5.56×45 (.223 Rem) AR mags to fit inside the lower. To move from .308 to .223, once the insert is in place, you simply switch the buffer spring and buffer, and then attach your .223 Rem upper.
You’ll find a detailed review and field test of the Colt 901 in the latest GunsAmerica Blog. The testers say the Colt 901 caliber-changing system works as advertised: “It can be adapted from .308/7.62, using standard P-Mags, to .223/5.56, using standard AR mags, and back again, in literally seconds. The design uses one proprietary part, and you have to swap out the recoil system. It is that simple, and it works fantastic…. What [Colt] did was to design a very simple part that adapts both the lug and the magazine size from one size upper to the other. The part itself is made from aluminum, and weighs exactly 3 ounces, including the captured steel push pin. It is simply an adapter, and its genius is in its simplicity.”
The GunsAmerica Review of the Colt 901 is worth reading if you’re interested in a dual-caliber AR. The review offers plenty of photos (zoomable to large size), with close-ups of the magwell insert and the buffer systems. In addition, the reviewers field-tested the Colt 901 with both .223 Rem and .308 Win uppers. Accuracy at 100 yards was not impressive (1.5″ group with the .308, about 2″ for the .223 version), but the reviewers believe the rifle could have shot better with a trigger upgrade.
Colt 901 Video from Military.com (2011 Unveiling)
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