The Unicorn of AR Piston Kits! 300blk!

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A quiet reliable piston driven 300 blk platform for the longest time was a unicorn in the industry with many manufacturers keeping their solutions under wraps or to prevent consumers from placing the blame on them when the advice given backfires. Because of this many shooters have been trying to modify their 5.56 piston kits to work with 300 Blackout by doing everything from drilling out the gas block to drilling out the gas port in the barrel and while some cases have proven successful many just throw in the towel and revert to back to direct impingement.

PhotoCredit: YouTube

That was until now! Adams Arms has created the first ever 300blk Piston conversion kit that will run EVERYTHING from subsonic to supers even when UNSUPPRESSED and works with a pistol length system.

Kit includes:

  • Patented One-Piece Low Mass Bolt Carrier
  • P Series Micro Block – Adjustable (5 Settings – 100%/74%/53%/32%/11%)
  • Upper Receiver Bushing
  • Bushing Installation Rod
  • Bolt Spring
  • Drive Rod with Bushing and Lightened Spring
  • Installation Instruction Card

The Adams Arms Piston System:

  • A short stroke free floating piston system.
  • Is Self-Cleaning.
  • Carbon and gases are expelled forward, away from operator.
  • Corrosive resistant coating processes.
  • Harmonics are not transferred into the barrel.
  • Doesn’t vent directly to atmospheric pressure; this eliminates flash signature and super sonic crack which is optimal for night vision and suppresses fire.
  • Has a Lifetime Warranty.


For 300BLK we only recommend a Pistol Gas Length (4.846″ from barrel extension to shoulder) and a Low Mass Carrier for optimal performance.

We recommend using a standard barrel nut or barrel nut with similar measurements for proper fit and function of the kit. Many aftermarket proprietary barrel nuts do not offer the clearance for the drive rod or proper seating of the spring and bushing.

Micro Gas Blocks should have the set screws torqued to 87 in-lbs

Installation Instructions: CLICK HERE

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