At this time your barreled upper receiver is ready for a handguard. The lightweight (9.07 oz.), 15-inch 6061-T6 aluminum ATLAS R-One handguard is one of our new favorites—due in part to its user-friendly and incredibly secure ratcheting Taper Lock Attachment System (ATLAS).
To put a “done” stamp on our upper receiver we used an Aero Precision phosphate-coated M16 bolt carrier group holding a Carpenter 158 steel bolt, along with an Aero Precision Ambidextrous Charging Handle with large, serrated and very-easy-to-grab latches.
With a flared magwell, integral, vented and drop-down trigger guard, recessed and clearly identified safety selector markings and various other features, Aero Precision’s M4E1 Enhanced Forged Lower Receiver (also in FDE) is tough to beat. To get it up and operational we used an Aero M4E1 Lower Parts Kit, which included a Magpul MOE handgrip (other grip options available).
One of the aspects of the M4E1 Enhanced Lower that we put in the “priceless” category is its threaded bolt-catch bore, which replaces the difficult-to-install roll pin with an easy-to-install threaded pin. The Real Avid Bench Block has a fixture to support the lower while installing the bolt catch.

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