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

Stoeger STR-9 Thinline
Stoeger STR-9 Thinline

Review: Stoeger STR-9 Thinline

The new Stoeger carry gun loses nothing—except some weight and girth. This is the Stoeger STR-9 Thinline.

5 Great Products for Your Next Hunt

These five products will help boost your chances at success in the field.

Small Calibers for Self-Defense: Addressing Common Myths & Criticisms

For decades, small cartridges like the .22 Long Rifle were derided as incapable rounds for defensive use and were even considered dangerous for the user by some. Today, those critiques deserve a second look.

New for 2026: HUXWRX Flow 9k PCC & Flow 9 M Suppressors

Continuing the legacy it first established as Operator Suppressor Systems, HUXWRX is still introducing new and mission-specific flow-through suppressors, with its latest products being the FLOW 9 M and FLOW 9k PCC.

Armed Citizen Stops Oregon Attack; NRA Reaffirms Importance of Law-Abiding Armed Citizenry

The National Rifle Association of America today issued a statement regarding yesterday’s act of violence in Oregon.

Gun of the Week: Tokarev TT-12 Pro

While there are several AR-style, semi-automatic shotguns on the market, the Tokarev TT-12 Pro has a few features you won’t find elsewhere. And it’s affordable, to boot.

Interests



Get the best of American Rifleman delivered to your inbox.