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Adams Arms AR-15 P2 Adjustable Gas Piston Pistol Upper Receiver Assembly 5.56x45mm NATO 7.5” Barrel



Product Information

Cartridge 5.56x45mm NATO
Material Aluminum
Barrel Length 7.5 Inches
Twist 1:7 Inches
Threads 1/2″-28
Sights No
Gas System Length Pistol
M4 Feed Ramps Yes
Upper Receiver Type A3 Flat-Top
Handguard Free Float M-LOK
Mil-Spec or Commercial Mil-Spec
Country of Origin United States of America
Compatible With

Delivery Information

Shipping Weight

4.565 Pounds

Product Overview

This Adams Arms P2 Adjustable Gas Piston Upper Assembly is chambered in 5.56x45mm NATO and comes ready to fire right out of the box after installation onto any standard AR-15 pistol or registered SBR lower receiver.  The P2 features a melonite finished, 7.5″ barrel with a 1 in 7″ twist, making it capable of stabilizing medium- to heavy-weight projectiles of up to 77 grains. The P2 configuration comes equipped with a free floating, Adams Arms M-LOK handguard. The low profile P-series Micro gas block is 40% lighter than previous railed versions and fits nicely under the rail. Together, the forged A3 flat-top upper and handguard create a long, uninterrupted top rail interface with ample room for mounting optics and/or iron sights.

The upper’s barrel has been finished inside and out with Adams Arms’ proprietary QPQ Melonite treatment that bonds with the metal on a molecular level. Also referred to as salt bath nitriding, this treatment produces an extremely hard, slick surface on steel that resists carbon adhesion and increases corrosion resistance, extending a barrel’s service life by reducing the friction produced inside the bore upon firing for a net decrease in bore surface wear over time. Nitriding converts the barrel steel’s surface without any build-up, retaining all of the benefits of traditional chrome lining without suffering the accuracy degradation commonly encountered due to uneven application of chrome inside the barrel’s bore. The end result is a barrel that’s capable of producing accuracy on par with a match stainless steel tube, while also exhibiting the longevity and resilience of a chrome lined, mil-spec barrel.

All Adams Arms uppers feature a short stroke gas piston operating system, which prevents hot gas and debris from being directed back into the action upon firing. The result is a rifle that runs cooler, cleaner and more reliably than those utilizing a standard direct gas impingement system of operation. To ensure that damage doesn’t occur to the buffer tube from carrier tilt, the bolt carrier is equipped with enlarged “skis” to help guide it into the receiver extension. The bolt carrier’s solid steel, 1-piece construction incorporates an integral piston strike face to guarantee integrity over time, while the bolt assembly is spring loaded for proper lock-up and to help reduce bolt bounce and cam pin wear. All piston components are finished in QPQ Melonite for corrosion resistance and easy cleaning/maintenance.


  • Free float M-LOK handguard
  • Extended A2 flash hider
  • P-Series Adjustable Micro gas block
  • Short stroke gas piston
  • Ambidextrous Charging Handle
  • Short stroke free floating piston system
  • Self-cleaning and corrosive resistant piston coating
  • Carbon and gases are expelled forward

Made In United States of America


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