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

The Six Hour Gun 1
The Six Hour Gun 1

The Six-Hour Gun: Saving a Family Heirloom

Simple math would have told anyone it wasn't worth fixing a $150 revolver. But to one family, this simple, common revolver meant everything.

Idaho Voters Choose the Winchester Model 1873 for their Official State Firearm

On November 3, Idaho voters picked the Winchester Model 1873 rifle (nicknamed the “Gun that Won the West,” in .44-40 cal.) as the leading candidate to be their state firearm.

PROOF Research Opens New Montana Facility

PROOF Research held a grand opening of its new manufacturing facility in Columbia Falls, Mont. at the end of October.

Making the Smith & Wesson Bodyguard 2.0

After more than 10 years, Smith & Wesson discontinued production of its original M&P Bodyguard .380 and began plans for a second-generation model. But the path to the Bodyguard 2.0 wasn't a linear process.

NRA-ILA: Election Results Put Second Amendment Rights Under Immediate Threat

NRA-ILA Executive Director John Commerford issued a statement following the 2026 midterm election results.

Short & Fresh: The Derya TM22 Fresh & RANX Mag Fed

Derya Arms now offers two radical versions of several of its traditional firearms with the new TM22 Fresh and RANX Mag Fed pistols.

Interests



Get the best of American Rifleman delivered to your inbox.