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CMMG
Overview
The CMMG AR-15 12.5" 300 Blackout MR Barrel is designed for optimized performance with a medium profile that balances weight and rigidity, making it ideal for various shooting applications. With a twist rate of 1:7, this barrel effectively stabilizes heavier projectiles, enhancing accuracy and terminal ballistics. The pistol-length gas system and .750 gas block diameter ensure reliable cycling, which is essential for builds tailored for short-barreled configurations or those seeking compact setups. This barrel is commonly integrated into builds that focus on the 300 Blackout caliber, particularly where a pistol gas system is preferred.
Specifications
Available Merchants(6)
Prices checked
Price Alert
October 2026 on GunPartPicker
CMMG AR15 12.5" 300BLK Mr Barrel ranked #80 of the 329 barrels builders added on GunPartPicker in October 2026. Builders have added it to their builds on GunPartPicker. Since April 2026, it ranks #161 of the 1,046 barrels builders have added.
It was in stock most times we checked in October 2026, but today 2 of the 6 retailers we track have it in stock. Buying today, the lowest price is $215.38 at Brownells, above October's low of $181.99, so a better deal may come back.
Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 37 retailers
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Frequently Built With
The part most often added in each category by the builds that include this one
Tacfire AR-15 Upper Receiver with Dust Cover and Forward Assist - UP01-C
Radian Raptor Charging Handle & Talon Safety Selector Combo - OD Green
PSA AR-15 Lower Safe/Fire - 1728
PSA AR-15 Bolt Carrier Group 5.56 Full-Auto Nitride MPI - 516446953
Spikes Tactical AR-15 Gas Tube Melonite Pistol
Rock River Arms Single Stage Trigger KIT, Black
Build Configuration Breakdown
Aggregated and anonymized data showing how builders use this product
PlatformBased on real build data showing which platform (AR-15, AR-10, AR-9) builders pair with this product.
Builds Featuring This Part
See all builds →Builds in the community that include the Cmmg Ar15 12.5" 300blk Mr Barrel
| Build | Parts | Total |
|---|---|---|
 | 15 | $1090.74 |
 | 21 | $1342.98 |
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