CMMG AR-15 .22LR End Cap Logo. This end cap can be installed in place of a receiver extension and buffer assembly by simply using a 3/8 hex wrench. The End Cap is compatible with all CMMG 22LR AR Conversion Kits as well as any AR15 that uses a dedicated CMMG 22LR BCG and barrel. Specifications for CMMG AR-15 .22LR End Cap: Manufacturer: CMMG Magazine Capacity: 0 Round Magazine Included: No Package Contents: CMMG AR-15 .22LR End Cap CMMG 22CA947: AR-15 .22LR End Cap Logo