Polymer80 G150 and RL556v3 Rhino: AR-15 80% Lower Receiver Guide

WH By Wade Hollis — FFL transfers, Delaware gun laws

Polymer80 made two AR-15 80% lowers. The G150 Phoenix Gen 2 is the plain, light receiver in black, gray, flat dark earth and OD green. The RL556v3 Rhino adds an integral trigger guard, a flared and curved magwell and a slightly thicker web. Both are reinforced polymer and both ship as a kit with the two-piece jig, drill bits and end mill.

Compatibility. Mil-spec AR-15 lower parts kit, mil-spec buffer tube, standard buffer and spring, any AR-15 upper. Polymer80 specified its own torque for the buffer tube castle nut and a specific pistol grip screw length, listed in the product specifications.

Finishing the frame. Clamp the two jig halves on the receiver, mill the fire-control pocket with the end mill in a drill press or hand drill, then drill the trigger, hammer and selector holes through the jig bushings. About an hour. The polymer cuts fast, so take shallow passes.

Magazines and holsters. Any STANAG AR-15 magazine. The Rhino’s flared magwell speeds reloads; the G150 uses a standard magwell.

Buying from Delaware Firearms. Frames, lowers and complete pistols transfer through your licensed FFL dealer with a background check. Jigs, tools, slides and parts ship directly to you. Delaware has no sales tax. Both lowers and the LR-308 and A9X variants are in Polymer80 AR Lowers.

Frequently asked questions

Is a polymer AR lower strong enough?

For 5.56 and .300 Blackout carbines, yes. Polymer80 reinforced the buffer tube boss and the takedown pin area, which are the failure points on cheaper polymer lowers. Do not over-torque the castle nut.