Exoskeleton's and AR's

Choosing a lower receiver for an AR

Blueprint for Colt lower receiver - circa 1994

An AR-15 (or AR-10) lower receiver is an exoskeleton for several of the functional parts of the rifle. It must be rock-solid.

A lower receiver holds the trigger, hammer, and safety selector switch in place; it accepts the magazine and holds it in place; the lower supports the bolt catch; it provides for attachment of the pistol grip; and the lower has an attachment point for the buffer tube and stock. And, the lower receiver has two takedown pins that attach the lower receiver to the upper receiver. These functional parts are all internal to or attached to the lower receiver.

Selecting a Lower Receiver

When you go shopping for lower receivers, you will find a lot of discussion about the materials. Lowers can be made from cast aluminum, billet aluminum, forged aluminum, steel, titanium, or polymer. The best ones, of course, are made from unobtanium but those are on infinite backorder.