Stripped, small pin, semi-auto lower receiver is precision machined from a durable, 7075 T6 aluminum forging. Stamped “Cal Multi,” this versatile mil-spec receiver can be the foundation for rifle builds on 5.56/.223, 6.5mm, 6.8mm, 300 AAC Blackout, 9mm Luger, or other chamberings that fit the standard AR-15 receiver. Holes, inletting and pin locations have been cut to final dimensions and accept standard AR-15 magazines and components. Clearly stamped safe/fire switch position indicators ensure that you can easily identify the service state of the rifle.
Aero Precision’s M4E1 Threaded Assembled Upper Receiver gives you the best of two worlds: that badass looks and robustness of a billet receiver plus the easy parts compatibility (and price!) of a traditional mil-spec upper. And it comes with two nit-picky jobs done for you: the forward assist and ejection port cover are already installed.