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

Youth Shooting Sports Growth
Youth Shooting Sports Growth

Growth in Youth Shooting Sports Signals Bright Future for the 2nd Amendment

Judging by the record number joining clubs and teams, mass-media’s disinformation and political rhetoric are losing their luster with today’s youth, who are making time to head to the range.

Go-Bag Essentials: 5 Key Products for Your Escape Kit

These five products will help you remain comfortable and safe should you need to bug out in a hurry due to natural or man-made disasters.

10 Things You (Probably) Didn't Know About The Smith & Wesson Model 29

Without a doubt, the Smith & Wesson Model 29 is one of the 20th century’s most shootable, collectible "superstar" revolvers. Here are a few little-known facts about the gun.

Packable Punch: Discreet Ways to Carry More Firepower

While folding and takedown firearms chambered for full-power rifle cartridges may be niche defensive tools, the dark situations in which they shine brightest aren’t going away anytime soon.

Southpaw Solution: Ruger Introduces Left-Handed American Gen II Ranch Rifles

Traditionally, Ruger has offered a range of left-handed rifle models for the southpaws among us, and now, the company's Gen II American rifles are available in a left-handed variant, starting with the Ranch models.

Gun of the Week: Kimber 1911 DS Warrior LW

In 2026, Kimber developed its 1911 DS Warrior, an American-made, double-stack design that is intended to be an affordable entry point into Kimber's double-stack handgun line.

Interests



Get the best of American Rifleman delivered to your inbox.