First Look: CMMG 5.7x28 mm AR Conversion

by
posted on January 15, 2020
** When you buy products through the links on our site, we may earn a commission that supports NRA's mission to protect, preserve and defend the Second Amendment. **
cmmg-inc-57x28mm-ar-conversion-magazine-upper-receiver-f.jpg
In 2020, the 5.7x28 mm cartridge is coming back in a big way, and CMMG joined multiple companies in offering a new option for fans of this high-velocity cartridge. Following up on the success of the company's Banshee chambered in 5.7x28 mm, CMMG now offers an AR-15 conversion package that allows shooters to mate their mil-spec AR-15 lower receiver with the company's 5.7x28 mm Radial Delayed Blowback upper-receiver group.

The key to this conversion lies in CMMG's 5.7 AR Conversion Magazine, which is designed to fit into standard AR-15 magazine wells while providing a reliable feed mechanism that's compatible with the company's 5.7x28 mm upper receiver. To convert any standard AR-15 to a 5.7 mm firearm, simply remove the existing upper-receiver group and replace it with a compatible, 5.7x28 mm upper receiver from CMMG. Once the upper receiver is installed, users can simply insert a CMMG 5.7 AR Conversion Magazine into the mil-spec magazine well.

In addition to allowing AR owners to experiment with the 5.7x28 mm cartridge without having to purchase an entirely new firearm, this CMMG conversion system maintains the controls and configuration of any existing AR-15 lower. If users have an enhanced trigger installed in their gun or optimized controls, they can continue using those components without having to invest in or learn an entirely new firearm. CMMG recommends the use of a standard carbine buffer and action spring to run the 5.7x28 mm conversion reliably, and the magazine provides last-round bolt hold-open capability.

A complete lineup of CMMG Banshee and Resolute upper receivers are compatible with the 5.7 AR Conversion Magazine. CMMG's Mk57 upper receivers can be had in 5", 8" and 16" barrel lengths, and the uppers ship complete with bolt-carrier group and charging handle. A single CMMG 5.7 AR Conversion Magazine holds 40 rounds of 5.7x28 mm, and the suggested retail price on the mag is $39.95. Suggested retail pricing on the Mk57 upper receiver complete with three 40-round magazines starts at $799.95. For more information on these conversion kits, visit cmmginc.com.


Latest

Japanese Type 38 Arisaka Ihtog 1
Japanese Type 38 Arisaka Ihtog 1

I Have This Old Gun: Japanese Type 38 "Arisaka"

Along with the Type 99, the Japanese Type 38 "Arisaka" was one of the main bolt-action battle rifles used by Japanese imperial forces during World War II.

New For 2025: Stoeger M3000 & P3000 Tactical

Stoeger Industries optimized its inertia-driven M3000 and pump-action P3000 shotgun designs for defensive and tactical use.

Tips & Techniques: Applying A Linseed Oil Finish (Without Turning Your Stock Into A Sticky Mess)

Linseed oil may be the oldest wood finish known to man, with evidence of linseed oil finishes being applied to wood as far back as ancient Egypt.

Rifleman Report: Proficiency Is Key

As the end of the calendar year approaches, and new firearms and related products continue to become available, we’re reminded that, while gear is important, training safely with it while developing familiarity is just as vital.

I Have This Old Gun: British Garate Revolver

World War I, as it would come to be known, rather took most powers by surprise. In 1914, Great Britain, which had not entered into a formal alliance with France and Russia, was expected by some to sit on the sidelines while the others went at it.

Beretta Commemorates 50th Anniversary Of 90 Series Pistol Family

Beretta's popular 90 Series handguns, including the iconic Beretta 92, celebrates 50 years of production in 2025, and to honor the milestone, the company has released a limited-edition variant.

Interests



Get the best of American Rifleman delivered to your inbox.