CMMG RDB 5.7x28mm

CMMG Inc. began in central Missouri in 2002 and quickly developed into a full-time business. Known for their Radial Delayed Blowback actions, CMMG is now offering their 5.7 AR Conversion Magazine. Holding 40 rounds of 5.7x28mm, this magazine fits mil-spec AR-15 lower receivers when paired with CMMG’s 5.7x28mm Radial Delayed Blowback upper.

The appeal of 5.7x28mm is that it is a small caliber with high velocity designed for a handgun and personal defense weapon (PDW). The cartridge was developed in response to NATO’s request for a replacement for the 9x19mm cartridge.

Any AR-15 can shoot 5.7x28mm using a CMMG 5.7x28mm Radial Delayed Blowback upper and 5.7x28mm AR Conversion Magazine. CMMG recommends using a standard carbine buffer and action spring to reliably cycle. The 5.7 AR Conversion Magazine also retains last round bolt hold-open functionality. The Radial Delayed Blowback has less felt recoil than direct blowback designs.

CMMG also offers complete firearms designed for 5.7 AR Conversion Magazines built with CMMG’s Mk4 lower receiver. The 5.7x28mm uppers are available in five, eight, and sixteen-inch barrel lengths. Or you can build your own. CMMG offers 5.7x28mm bolt and barrel kits with the same barrel options.

For more information, visit or call 660/248-2293.

Read more in the April 2020 issue.

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