BCM® Standard 12.5" 300 BLACKOUT Complete Upper Receiver Group w/ MCMR-10 Handguard

MSRP: $1,081.50
Your Price: $803.45
(You save $278.05 )
300 BLK
Barrel Length:
Barrel Style:
Stock Status:

Out of stock

About the BCM® Standard 12.5" 300 BLACKOUT Complete Upper Receiver w/ MCMR-10 Handguard

  • Continuous taper barrel profile designed for optimal weight, balance, and performance.
  • Barrel profile fluted toward the rear near chamber area - Increases strength and heat dissipation.
  • Tapered barrel profile out front, for easier maneuverability.
  • No sharp handguard cap shoulder for improved barrel harmonics and improved accuracy.
  • Muzzle threaded in standard 30 cal (5/8x24).

Whats included: 

  • Includes MCMR-10 Handguard
  • Includes MCMR-SM (MCMR Sling Mount)
  • Includes One 3" Picatinny Rail Section
  • Includes BCM® Comp Mod 1 - 762/300 BLK
BCM® has taken great care to ensure the best possible performance and interchangeability. However, due to the large operational range of 300 Blackout ammunition in the market place, BCM® cannot guarantee function will all ammunition types in all conditions.
These barrels were designed to run with a H3 buffer with high velocity ammo. If running subsonic ammunition, it is recommended to run your suppressor and a carbine buffer. Fine tuning may be required in limited instances based on ammo and buffer choices that work best for the desired application. BCM® also recommends running the Crane O-ring (provided with all BCM® Bolt Carrier Groups) over the extractor with 300 Blackout.


  • Caliber: 300 Blackout
  • Barrel Length: 12.5"
  • Barrel Material: 11595E Spec Steel
  • Barrel Finish: Manganese Phosphate (Mil-Spec A-A-59267)
  • Bore & Chamber: Chrome Lined
  • Weight: 2.5 lbs
  • Twist Rate: 1:7
  • Gas System: Pistol
  • Muzzle Device: BCM® Comp Mod 1 (762/300BLK)
  • Muzzle Threads: 5/8x24
  • Handguard: MCMR-10

Shop Related Products:

Want to see more upper receivers? Click the links below to view more BCM® AR complete uppers!


Bravo Company builds: Life Saving Tools™
Copyright 2023 Bravo Company MFG, Inc.
***This product contains chemicals/materials known to the State of California to cause cancer and other reproductive harm. To learn more, visit www.p65warnings.ca.gov.***

11 Reviews

  • 5
    12.5" 300BLK

    I've had this for about a month now, and wanted to wait until I got at least 500 rds. through it. The first 250 rds. I used an LVPO and 125 gr. I was getting 1 MOA well past 100 yds.

    The other 250 rds. was on a red dot with subsonic ammo and it ran like a dream both suppressed and un-suppressed.

    As always, good job BCM for making a reliable product.

  • 5

    I can’t say enough about this upper. Had a chance to hit the range and this thing is accurate. I had big plans for this build. I was going to have it coated to match a FDE lower build. After receiving the upper plans changed , I just can’t bring myself to cover up all the fine work and detail this upper has. Great work guys will be buying more from BCM

  • 5
    Top notch

    I love shooting this! Accurate and looks sharp. I want to get another now!

  • 5
    12.5 Mcmr Blackout Upper

    Using for home defense and would trust my life with it. Going to buy another one. Outstanding! The enhanced and fluted barrel was rated highly by Mr Gunsngear.

  • 5
    Love this upper!

    I already had the 9 inch version of this rigged suppressed for home defense. After watching Mrgunsngear's videos on barrel length I wanted to take advantage of the supersonic capabilities of the 300blk as well. 12.5 seems to be a sweet spot at you still can maintain subsonic speeds with heavier loads that you can't with longer barrels while maximizing wallop with lighter loads. Ran it for thenfirst time this weekend with subs and supers. Was maintaining 1-2 inch groups at 100 yards using a PA 1-6. The added rail real estate also makes running lights, sling mounts, and offset BUIS much easier than the 9 inch.

  • 5
    As advertised

    Solid upper and rail set up.

  • 5
    Always buy BCM

    Came in a week, all parts locked up tight, and shot tight groups first time on the range

  • 5
    Perfect Upper

    Purchased this complete upper for my first lower build and couldn’t be more pleased with the product. Shipping was very fast.

  • 5
    Customer review

    The best upper for the money hands down. Love BCM anything!