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RDB was an advancement from straight blowback. Compact action RDB was an advancement to the original RDB. This fixed ejector upper is designed to be the most compact 9mm AR. CMMG's 9mm RDB uppers are designed to work exclusively with CMMG MkGs, Mk17, and Mk9 9mm lowers, or with mil-spec AR15 lowers using 9mm conversion magazines. Specifications for CMMG 9mm 5in Banshee Fixed Ejector Upper Group Receiver: Manufacturer: CMMG Caliber: 9mm Luger Overall Length: 13.7 in Barrel Length: 5 in Barrel Twist Rate: 1-10 Threads per Inch: 1/2x28 Muzzle Device: CMMG Zeroed Muzzle Brake Finish: Cerakote Fabric/Material: Aluminum Gun Rail: M-LOK Weight: 2.6 lb Barrel Material: 4140 Chrome Moly Vanadium Magazine Included: No Package Contents: CMMG 9mm 5in Banshee Fixed Ejector Upper Group Receiver
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