Adams Arms AR-15 Base A3 Gas Piston Upper Receiver Assembly 5.45x39mm 16" Barrel

Product #: 430329 Adams Arms #: UA-16-C-B-545 UPC #: 854262002261
Date expected in stock: Overdue
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This Adams Arms AR-15 A3 Base Carbine Gas Piston Upper Assembly is chambered for the cheap and plentiful 5.45x39mm round, and comes ready to fire right out of the box after installation onto any standard AR-15 lower receiver. This Base Carbine upper comes equipped with a 16" melonite-finished barrel, A2 flash hider, ion-bonded bolt carrier group, charging handle assembly, picatinny rail gas block, 30-round magazine, delta ring assembly and a set of polymer M4-style handguards. Additional features include a forged A3 flat-top configuration that's ready to accept the shooter's choice of optic and/or rear iron sight, M4 feed ramps to help ensure reliable feeding and functioning during rapid strings of fire, and a carbine length gas system. Also includes a Wolff extra power hammer spring to ensure proper ignition of foreign military surplus ammunition with hard primers.

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. The QPQ Melonite finish protecting the barrel, piston components and flash hider is so corrosion resistant and durable that it is not adversely affected by prolonged exposure to the corrosive primer residue that's often left behind after firing military surplus 5.45x39mm ammo. While immediate cleaning of all steel parts after shooting corrosive ammunition is still recommended, it is not necessary.

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.

Technical Information
  • Upper Receiver: A3 Flat-Top, Forged
  • Barrel Length: 16"
  • Barrel Contour: M4
  • Barrel Material: 4150 Chrome Moly Vanadium Steel
  • Muzzle Thread Pattern: 1/2"-28
  • Chrome Lined: No
  • Barrel Finish: QPQ Melonite / Black Nitride
  • Twist Rate: 1 in 8"
  • Chamber: 5.45x39mm
  • M4 Feed Ramps: Yes
  • Muzzle Device: A2 Flash Hider
  • Gas System Length: Carbine, Short Stroke Piston Operated
  • Gas Block Diameter: 0.750"
  • Handguard: 2-Piece Polymer M4-Style
  • Sights: None, Single Rail Gas Block
  • Bolt Carrier Assembly Included: Yes
  • Bolt Carrier Type: 1-Piece w/Integral Piston Strike Face
  • Extras: One 30-Rnd Magazine, Wolff Extra Power Hammer Spring
  • Weight: 4.19 lbs

Technical Notes
  • Safe for use with Corrosive Mil-Surplus Ammo
  • Barrel, Piston Components, Gas Block & Flash Hider are all QPQ Melonite Finished
  • Bolt & Carrier Assembly are finished with Ion-Bond

Please Note: Installation of AR-15 upper assemblies with certain features including, but not limited to: flash hiders, bayonet lugs, and threaded muzzles may violate state and/or local laws.

Product Videos

  • Adams Arms Video
  • Adams Arms Video
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