Cmmg Ar Mk 57 Conversion Kit 22Lr W/ 3 10-Rd Mags

The CMMG AR Mk 57 Conversion Kit in .22 LR is your ticket to affordable, high-volume plinking without retiring your 5.7x28mm upper receiver. If you own a CMMG Mk57 upper and want to run cheap .22 LR ammunition for practice and fun at the range, this drop-in conversion kit swaps the bolt-carrier group to instantly transform your rifle into a .22 LR shooter. It's a smart way to get the most out of a single upper receiver—no gunsmithing, no tools required.

The kit is built on simplicity: remove your existing Mk57 bolt-carrier group and drop in the .22 LR conversion unit. Attach your Mk57 upper to any mil-spec AR-15 lower receiver, load one of the three included 10-round magazines, and you're ready to shoot. Because .22 LR brass and ammunition are plentiful and inexpensive, you'll spend less per round and more time at the range honing your fundamentals or just enjoying a day of marksmanship without the recoil and noise of centerfire rounds.

The included magazines are compatible with all mil-spec AR-15 and Mk4 magazine wells, so they'll work with standard AR platforms. This kit is purpose-built for shooters who already have a Mk57 upper and want the flexibility to train affordably or introduce new shooters to the platform without breaking the bank on ammunition.

Key Features

• Drop-in conversion from 5.7x28mm to .22 LR—no tools or gunsmithing required
• Includes three 10-round .22 LR magazines
• Magazines compatible with mil-spec AR-15 and Mk4 magazine wells
• Transforms your CMMG Mk57 upper into an affordable training and plinking rifle
• Simple bolt-carrier group swap keeps your Mk57 upper receiver intact for fast caliber switching

Specifications

Frequently Asked Questions

Will this .22 LR conversion kit work with my AR-15 lower receiver?

Yes. You'll use the CMMG Mk57 upper receiver with this conversion kit mounted on any mil-spec AR-15 lower receiver. The included magazines are compatible with standard mil-spec AR-15 magazine wells.

Do I need any gunsmithing or tools to install this conversion kit?

No. The kit is designed as a drop-in replacement. Simply remove your existing Mk57 bolt-carrier group and replace it with the .22 LR conversion unit. No tools required.

Can I switch back to 5.7x28mm after installing this .22 LR conversion?

Yes. Because the conversion is a bolt-carrier group swap, you can switch back to 5.7x28mm by reinstalling your original Mk57 bolt-carrier group.

What magazines come with this kit and will they fit other AR platforms?

The kit includes three 10-round .22 LR magazines. These magazines are compatible with all mil-spec AR-15 and Mk4 magazine wells, making them versatile across standard AR platforms.