New for 2020: CMMG 5.7x28 mm AR Magazine and Conversion Kit

CMMG has released a 5.7 AR Conversion Magazine that holds 40 rounds of 5.7x28 mm. It fits and functions in a mil-spec AR-15 lower receiver when paired with the company’s 5.7x28 mm Radial Delayed Blowback upper receiver. The magazine and conversion allow shooters to enjoy the advantages of CMMG’s operating system, without surrendering the familiar location and feel of an AR-15's firearm controls.

The process of converting an AR-15 to shoot the pistol cartridge is simple and quick. First, attach a CMMG 5.7x28 mm Radial Delayed Blowback complete upper receiver to an existing AR-15 lower. Then insert the company’s new magazine and you’re ready to function test. The company recommends using a standards carbine buffer and action spring to reliably cycle the action in this configuration. The 5.7 AR Conversion Magazine also retains last-round bolt hold-open functionality.

Bullets leave a gun at high velocity with the small-caliber 5.7x28 mm cartridge, which makes it particularly appealing for personal-defense applications. It was developed in response to NATO’s request for a replacement for the 9 mm cartridge. CMMG’s patented Radial Delayed Blowback system of operation has quickly gained traction in pistol-caliber carbines, primarily due to reduction in perceived recoil when compared to that of traditional direct blowback designs.   

The company offers a complete line of firearms and upper receivers in its Banshee and Resolute lines that chamber the cartridge. Three different barrel lengths are available—5, 8 and 16 inches—and all employ the firm’s system of operation and new magazine. 

CMMG will also offer 5.7x28 mm bolt and barrel kits in 5-, 8- and 16-inch barrel lengths for gun builders. These kits will be compatible with the company’s Mk57 lower receivers, as well as Mk4/AR-15 lower receivers when used with the new CMMG 5.7 AR Conversion Magazines.