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GM-M15 20" M16A1 5.56x45mm 1:12 twist


Product Description

  • Caliber- 5.56x45mm
  • Twist Rate- 1:12
  • Length- 20"
  • Profile- M16A1 Pencil Under "See 1 more picture" there is a detailed drawing of this barrel.
  • Finish- Chrome Line Phosphate
  • Gas System Length- Rifle
  • Gas Block OD- .625+-(.001)
  • Steel Type- 41V50
  • Thread Pitch- 1/2x28
  • Weight- 1.70lbs

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Product Reviews

Showing reviews 1-5 of 82 | Next

  1. Retro Build Big + and (-) 5 Star Review

    Posted by on 26th Jun 2022

    I have been selling your barrels for the 16 retros since I became one of you dealers, they are still the top of the line for the A1 retros. However you joined the rest of the premium barrel manufacturers, by either discontinuing or changing gas tube length to mid-length system which eliminates the 16" 5.56 pencil barrel carbine RETRO'S for everyone.

  2. 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

  3. 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.

  4. 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.

  5. 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 !


Showing reviews 1-5 of 82 | Next