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GM-M15 20" M16 A1 5.56mm 1:12 twist


Product Description

5.56mm, 1:12 twist, 20", 41V50 steel, , weighs 1.75 lbs., fully machined and assembled with M16 extension, chrome line bore and chamber, drilled gas port, phosphate finish, button rifled, air gauged, stress relieved. 1960s era pencil profile, muzzle threading 1/2 x 28.  

Barrel is not pinned for front site.

Under "See 1 more picture" there is a detailed drawing of this barrel. 

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Product Reviews

Showing reviews 1-5 of 81 | Next

  1. Educate urself on barrel twist rates! 5 Star Review

    Posted by on 5th Feb 2021

    I made a mistake by not understanding the barrel twist rates and the grain of the bullet you should be using ! The higher the second # is preferable to lower grained bullets . That being said I don’t reload and don’t have an unlimited budget I typically buy bulk Ammo that I find is 55 to 62 grain . When I built this rifle it was for pushing the 5.56 or 223 to its max ranges. Unfortunately I have never ran across 40 -45 grain bulk Ammo . My other GM barrels two 16” 1:7 are superior in accuracy and all run even steel case Ammo flawlessly. The 20” struggles on long range so educate urself before investing . GM is best bang for da buck period! DK

  2. Appears to be as good as it gets 5 Star Review

    Posted by on 19th Aug 2020

    After reading reviews I choose GM barrels for My M16a1 replica. Friendly and good to work with, they sent Me a fine barrel that meets all my expectations.

  3. Great product great service 5 Star Review

    Posted by on 10th May 2020

    The barrel is first rate in every way. Completely meets the standard for my retro build.

  4. High Qualiy Barrel 5 Star Review

    Posted by on 17th Apr 2020

    I have purchased many barrels from Green Mountain Barrel. They manufacture the best in the industry. Their shipping is super fast, and customer service is fantastic. Thanks again GMB for providing the best quality barrels !


  5. accurate. 5 Star Review

    Posted by on 23rd Jul 2019

    I’ve free floated this barrel in a MI combat rail, and it achieves consistent near MOA performance with Federal xm193 55gn. 1 7/8” at 200 yards, 3 1/4” at 300 yards, and 4 1/2” at 400 yards ( consistent 5 shot groups). Top quality performance for plain military ball nearly makes hand loading unnecessary. A true testament to quality.

Showing reviews 1-5 of 81 | Next