The CMMG 99D517A Replacement Barrel and Bolt Carrier Group Kit is engineered for shooters looking to build a high-performance Pistol Caliber Carbine (PCC) chambered in 9mm Luger. Featuring CMMG's Patent Pending Radial Delayed Blowback (RDB) system, this kit delivers a superior shooting experience compared to conventional direct blowback designs. The RDB system forces the bolt to rotate and unlock before cycling, effectively slowing the bolt carrier group. This innovative mechanism allows for a lighter BCG overall and noticeably reduces felt recoil versus straight blowback systems. The 8-inch Chrome Moly Steel barrel is treated with a Salt Bath Nitride (Black Nitride) finish for outstanding corrosion resistance and long-term durability. The kit is designed to work exclusively with mil-spec AR-15 upper receivers that feature a modified ejection port, such as CMMG's MkG and MkGs uppers, and is compatible with most mil-spec AR-15 lowers when paired with 9mm AR Conversion magazines, as well as CMMG's MkGs, Mk17, and Mk9 lowers. Note: Older Mk9 lowers will require a CMMG retrofit kit to convert to Radial Delayed Blowback compatibility.
Product Highlights
- Patent Pending Radial Delayed Blowback (RDB) System - Forces the bolt to rotate and unlock before cycling, reducing bolt velocity and felt recoil compared to traditional straight blowback designs.
- 8-Inch Chrome Moly Steel Barrel - Precision-crafted from durable Chrome Moly Steel with a 1:10" twist rate, optimized for 9mm Luger performance in a compact pistol or carbine build.
- Salt Bath Nitride (Black Nitride) Finish - Provides superior surface hardness, corrosion resistance, and reduced friction for reliable performance in demanding conditions.
- Broad AR-Platform Compatibility - Designed to fit mil-spec AR-15 upper receivers with a modified ejection port and most mil-spec AR-15 lowers with 9mm AR Conversion magazines, including CMMG MkG, MkGs, Mk17, and Mk9 lowers.
- Complete Barrel and BCG Kit - Includes both the barrel and a matched Bolt Carrier Group, providing everything needed for a seamless PCC upper build.
Specs
- Brand: CMMG
- Manufacturer Part Number (MPN): 99D517A
- UPC: 815835019802
- Caliber: 9mm Luger
- Barrel Length: 8 inches
- Twist Rate: 1:10"
- Barrel Material: Chrome Moly Steel
- Finish: Salt Bath Nitride (Black Nitride)
- Operating System: Radial Delayed Blowback (RDB)
- Platform Compatibility: Mil-Spec AR-15 with modified ejection port (e.g., CMMG MkG/MkGs upper receivers); compatible with most mil-spec AR-15 lowers using 9mm AR Conversion mags, and CMMG MkGs, Mk17, Mk9 lowers
- Kit Contents: Replacement Barrel and Bolt Carrier Group (BCG)
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