Editor’s Choice: CMMG 5.7 mm Conversion Kit

by
posted on May 19, 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. **
cmmgkit.jpg

CMMG has tapped into a cartridge that has long been a niche round for a select few enthusiasts: the 5.7x28 mm FN. The cartridge underwent a recent resurgence with the launch of the CMMG Mk57 Banshee in 2019 and received a bigger boost with the 2020 launch of the Ruger-57.

Now CMMG proves that it wasn’t finished with the 5.7 mm by rolling out a conversion kit for today’s AR-15 rifle owners. The Mk57 Banshee fed from Five-SeveN magazines, requiring added investment for anyone not already sitting on a stock of them.

However, the Mk57 AR Conversion Kit provides an opportunity for owners of mil-spec AR-15 lower receivers to get in on the 5.7 mm fun. The conversion 
includes a STANAG-size magazine that provides a reliable feeding platform for the company’s 5.7x28 mm FN upper receiver.

Best of all, these proprietary magazines hold 40 rounds each, providing twice the capacity of FN Five-SeveN pistol magazines. For more information on these CMMG 5.7 Conversion Kits, visit
cmmginc.com.

Latest

firing a musket rifle
firing a musket rifle

Today’s Makers of Yesterday’s Firearms

Original firearms from the American Revolution era are valuable and best preserved for posterity. For those who want to shoot them, several modern makers offer quality reproductions.

Left Turn (Bolt): Tikka's New Left-Handed T3x Ace Rifles

Lefties of the world unite and rejoice, as Tikka has announced left-hand versions of its award-winning T3x Ace chassis rifles.

The Armed Citizen® Sept. 14, 2026

Read today's "The Armed Citizen" entry for real stories of law-abiding citizens, past and present, who used their firearms to save lives.

Skills Check: Rifle Standard Delta 2

Carbine performance is all about maintaining control. The Rifle Standard Delta 2 is a drill that pressures recoil control, visual discipline and cadence as distance decreases and time compresses.

Gun Sales Up for the 7th Month in a Row in 2026

The National Shooting Sports Foundation’s (NSSF) estimate of last month’s gun sales was up 2.2 percent compared to August 2025.

Caring For & Feeding Your Cap-and-Ball Revolvers

Compared to pistoleros of the 19th century, today’s handgunners have it easy. It's not enough just to get an old-school, cap-and-ball revolver. You also need to acquire everything to shoot and clean it.

Interests



Get the best of American Rifleman delivered to your inbox.