Mk57 .22LR Conversion | CmmG’s Newest Conversion Kit

CmmG 5.7x28mm to .22LR Conversion Kit

CMMG has just expanded its product line by adding the Mk57 .22LR AR Conversion Kit.

Now you can easily convert your CMMG 5.7x28mm upper receiver group into a .22LR. All you have to do is swap out the bolt-carrier group, paired with the 5.5x28mm upper and any Mil-Spec AR15/Mk4 lower receiver.

Make sure you’re also using a CMMG dedicated .22LR magazine.

CMMG Mk57 .22 LR Conversion Kit.

Image Source: OreGear.

CmmG tells us they make these conversion kits because they pride themselves on caliber flexibility. It gives the shooter the ability to shoot multiple calibers with one lower, which has its obvious advantages, such as reduced cost and more storage availability.

The folks over at OneGear did a video review.

So, If you happen to have a CMMG Mk57 upper and convert it to shoot a .22LR, you’re able to reduce cost because your rounds are less expensive.

CMMG Mk57 .22 LR Conversion Kit

Image Source: OreGear.

Also, If you’re concerned about ammo prices, we’re told you can take advantage of cost-effective rimfire training.

CmmG says it’s the ultimate tool for both young and first-time shooters.

.22 LR Conversion Kit Details

  • Dedicated bolt-carrier group
  • Your choice of one or three 25-rd magazine(s)—10rd magazine available in states with mag restrictions.
  • No tools required for installation
  • Made of stainless steel

Not compatible with Mk57 Lower Groups or 5.56/.223 uppers.

MSRP: $199.95 to $229.95.

For more information on the Mk57 .22LR Conversion Kit, you can visit

Pistol mags: you need some? We have ’em for every conceivable handgun make and model.

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Ashley Bunch is the first Tennesse-born Mag Life…we think. She’s an Air Force Security Forces veteran and former dog-handler-turned-journalist (like, real journalist, with an advanced degree and previous internships at big publications and everything). As you might expect from someone who works with us, she’s a bit of a smartass, a dedicated student of the hoplological arts (and the recent recipient of a Masters Degree in Psychology!), an ardent traveler, and more than a bit of a foodie. Ashley is a dangerous girl, particularly if your first name is Channel, Flathead, or Blue — Bunch has kilt and eaten many an insolent catfish. She’d rather be camping and fishing than just camping, just camping rather than just hiking, and just hiking rather than sitting at home. If she is sitting at home, however, there’s likely a big damn jar of sweet tea and a whole pile of books somewhere nearby.

  • TZMe

    Thanks for the article. It’s nice that CMMG gives people an option for that particular upper. I’d like to get one in 2-3 years or so, need to first build one more custom AR9 pistol, 6mm ARC (maybe 6.5 Grendel depending on how 6mm ARC goes in 6-8 months). Then a pistol AR15 5.56 first. Slowly gathering parts here and there.
    I’ve had your standard AR15 CMMG 22lr kit going on 5+ yrs. IIRC and had an issue with one of the parts (usually shoot 2-3k of 22lr just in the summer months outside). So was very impressed with your customer care. Got that collar for a dedicated custom AR22 and it works GREAT.