Aero Precision’s M4E1 5.56mm Mid-Length Upper Receiver comes fully assembled, lacking only a bolt/carrier group and charging handle - the two components most often replaced by customizers. "Mid-Length" refers to the gas tube, which is longer than the standard carbine tube to slow down gas velocity and actually improve reliability in cycling. This is actually a carbine upper, available with either a military 14.5" or civilian 16" barrel (see Gun Tech Note below).

The core of the M4E1 5.56mm Mid-Length Upper Receiver is Aero’s forged M4E1 receiver that combines the looks of a machined receiver with "mil-spec" parts compatibility (including BCG and charging handle). It’s mated to Aero’s latest Gen 2 Enhanced M-LOK Handguard to form a monolithic assembly with a full-length Picatinny top rail, and plenty of attachment points for M-LOK-accessories. QD sling swivel sockets at the 3/6/9 o’clock positions. The extended handguard covers the low-profile gas block. Texturing milled into the flats gives you an enhanced grasping surface - plus, it adds to your gun’s unique appearance.

FEATURES

• Forged 7075 T6 aluminum receiver, Mil 8625 Type 3 Class 2 hardcoat anodized
• Ejection port cover & forward assist installed
• 4150 chrome-moly-vanadium barrel, 1-7" rifling, black QPQ finish
• Chambered for 5.56x45 NATO; accepts .223 Remington, too
• MID-LENGTH gas system
• Handguard: 1.78" inside diameter clears most muzzle devices and 1.5" suppressors
• A2-style flash suppressor installed - NOT pinned or welded
• 1/2"-28 tpi muzzle threads
• .250" dia. pivot/takedown pin holes
• Bolt/carrier group & charging handle NOT included
• All NFA rules apply

Brownells Gun Tech™ Note: The M4E1 5.56mm Mid-Length Upper Receiver is available with a 14.5" or 16" barrel. The flash suppressor on the 14.5" barrel is not pinned or welded in place. Per the National Firearms Act, the muzzle device MUST be pinned and welded to achieve the minimum 16" OAL for a civilian rifle build. The 16" barreled upper has sufficient barrel length to meet NFA requirements without permanently attaching the flash suppressor.