Adams Arms AR-15 Piston Kits



Adams Arms’s piston kit converts your standard direct impingement rifle to a clean, cool, reliable system without extensive modifications. Our patented piston system is a drop-in system that works on any mil-spec AR-15 and is compatible with most standard AR-15 parts. Our kits have been treated by various coating applications to increase Durability, Lubricity, and Longevity, and come with a Lifetime Warranty.

The Adams Arms Retro-Fit Piston Drive System uses the same gas port on the barrel to work the action of our inverted piston. Instead of directing the gases into the receiver, they go into a gas plug and drive rod sleeve invented by Adams Arms. The gases are contained inside the drive rod sleeve and push the bolt carrier rearward using the gas pressure to cycle the action.

Adams Arms’s proprietary operating systems mechanically actuate the bolt carrier external of the receiver. This keeps the internal receiver and all the critical moving parts clean and free from heat and carbon build up.

Here are some of the main differences when using the Adams Arms Operating System:

Short Stroke Free Floating Piston System
Self Cleaning
Carbon and gases are expelled forward, away from the operator
Bolt Carrier Group and other critical components remain cool and clean
Corrosive resistant coating processes
Harmonics are not transferred into the barrel
Adjustable gas settings for various applications
Doesn’t vent direct to atmospheric pressure; this eliminates flash signature and supersonic crack which is optimal for night vision and suppressed fire

To select the correct length kit, use the following measurements:

Pistol: 4.846″ from barrel extension to shoulder
Carbine: 7.866″ from barrel extension to shoulder
Mid: 9.866″ from barrel extension to shoulder
Rifle: 13.241″ from barrel extension to shoulder
For 300BLK we only recommend a Pistol Gas Length and a Low Mass Carrier for optimal performance.

Adams Arms recommends 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

*Ships free directly from Adams Arms, may require backorder.

Additional information


Standard Picatinny Block, P-Series Adjustable Micro Block, 300BLK Piston Kit

System Length

Pistol, Carbine, Mid-Length, Rifle

Bolt Carrier Group

Standard Carrier, Standard Left-Handed Carrier, Nickel Boron Carrier +$10, Low Mass Bolt Carrier +$30, Low Mass Nickel Boron Carrier +$40