Smyth Busters: Are Polymer AR-15 Lowers Any Good?

"They're made of plastic. Polymer AR-15 lowers can't be as good / strong / reliable as aluminum lowers!" That's the myth Brownells Gun Techs™ Steve Ostrem and Caleb Savant take on today: Are polymer AR-15 lowers receivers inferior to traditional aluminum lowers? OK, maybe there is a grain of truth here because some EARLY polymer AR-15 lowers had quality, strength, and/or durability problems. But polymer receivers have come a long way in the last 25 or 30 years. The main stress point on an AR-15 lower is just in front of and below the place where the buffer tube screws into the rear of the receiver. Much of the force of the bolt slamming rearwards is directed there, and it can be a failure point, especially if the gun is overgassed. But a properly designed polymer lower like the KE Arms KP-15 is reinforced there and at other stress points (including around the pivot and takedown pin holes) to handle the forces involved in operating an AR-15. As for the durability of polymer, think of all the Glock® pistols that have been built - and run hard - in the last 40 years! So the myth is BUSTED. A well-engineered, well-made polymer lower is as good as an aluminum receiver.