World’s First 5.7x28mm to .22LR Conversion Kit
CMMG expands on the popular .22LR Conversion Kit with the addition of the Mk57 .22LR AR Conversion Kit. Easily convert your CMMG 5.7x28mm upper receiver group into a .22LR by swapping the bolt-carrier group, paired with the 5.7x28mm upper and any Mil-Spec AR15/Mk4 lower receiver, while using a dedicated CMMG .22LR magazine.