One piece forged upper receiver

Lightweight 15" ATLAS S-ONE free float M-LOK rail

Blended flat top receiver rail

16" M4 contour 41V50 chromoly vanadium steel barrel with durable nitride finish is high pressure tested and magnetic particle inspected

1:7 twist stabilizes even the heaviest 5.56 NATO bullets

Matching M4 feed ramps for receiver and barrel

Billet aesthetics without the billet cost or weight

Fully compatible with standard AR-15 bolt carrier groups and charging handles (available separately)

Effective A2 flash hider

The Aero Precision M4E1 Threaded AR-15 Barreled Upper Receiver is perfect for shooters who are looking for a little more out of their build. The unique receiver forging blends seamlessly into the lightweight ATLAS S-ONE free float M-LOK handguard. The billet look comes without the weight and cost. The barrel nut with taper lock mount allows for an incredibly rigid free floating rail, meaning your sights and lasers will be deflected less than traditional options will be when shooting from the prone or supported.The ATLAS S-ONE free float M-LOK handguard features an interrupted top picatinny rail, allowing for enhanced ergonomics and reduced weight in an area that very few shooters actually utilize for accessories. Instead the top of the handguard is equipped with indexing grooves for a sure grip when driving the muzzle. The M-LOK slots at the 3, 6, and 9 o'clock positions are ready to accept your favorite lights, lasers, and grips, while the integrated QD sling swivel sockets ensure you don't need to waste accessory space for a dedicated mount. The ATLAS uses a functional and aesthetically pleasing taper-lock system for rock solid mounting.Under the handguard is a 16" 41V50 chrome moly vanadium steel barrel. Chambered for the incredibly common 5.56 NATO, the barrel features 1:7 twist rifling that will stabilize the full range of bullets available up to 77-grain. The balanced M4 contour features a reliable carbine length gas system fed by a low profile gas block. The durable inky black salt bath nitride finish is exceptionally corrosion resistant and does not negatively impact accuracy the way old school hard chrome linings can. Threaded 1/2x28, the barrel is ready to accept your favorite AR-15 muzzle brakes, compensators, or flash hiders, and even ships with the highly effective A2 style bird cage flash hider.The Aero Precision M4E1 Threaded AR-15 barreled upper receiver perfectly blends precision machining, quality components, and eye-catching ergonomics perfect for nearly any build, simply add your favorite sights, bolt carrier group, and charging handle.