CMMG Replacement Barrel Kit Features The CMMG replacement barrel kit pairs its 4140 chromoly barrel with a matched bolt carrier group specifically tuned for reliable .22 LR function avoiding the feeding and extraction issues that can occur when rimfire conversions use mismatched components. The salt bath nitride finish on the barrel resists corrosion and wear from repeated firing extending the service life of the conversion beyond what a simple blued finish would offer. CMMG notes that best performance comes from using a round style hammer as notched hammers can cause function issues and that 36 grain plated nose bullets have proven to be the most reliable choice for cycling. Because the kit is designed to bolt directly onto an existing AR-15 upper shooters can convert their centerfire rifle to inexpensive rimfire ammunition for practice sessions without the cost of a dedicated .22 LR rifle. The included bolt carrier group means the only additional purchase needed to complete the conversion is a compatible magazine. For AR-15 owners looking for a cost effective way to add high volume rimfire training to their existing platform the CMMG replacement barrel kit is available for sale at GrabAGun. CMMG Replacement Barrel Kit Specifications Brand: CMMG Fits: AR-15 / Mk4 Caliber: .22 LR Barrel Length: 16.10 Barrel Material: 4140 Chromoly Steel Barrel Finish: Salt Bath Nitride Twist: 1:16 Thread Pattern: 1/2x28 Includes: Bolt Carrier Group Color: Black Available At: GrabAGun