RL556v3 vs G150 Phoenix2: choosing a Polymer80 AR-15 lower

Polymer80 makes two polymer AR-15 80% lowers and they are not interchangeable in the details that matter: grip, buffer housing and jig.

RL556v3

Solid-core reinforced polymer with a flared magwell and a beefier buffer tube housing than the earlier RL556. The pistol grip area uses a threadless design specific to Polymer80: the grip is retained without the usual screw into the receiver. It ships alone or with its own jig, trigger-hole drill guide, bits and end mill.

G150 Phoenix2

Also reinforced polymer, with an integrated trigger guard moulded into the receiver and a threaded, reinforced buffer tube housing, so a standard castle nut and end plate install like a metal lower. Uses the G150 jig. Sold as a kit, receiver-only, and in 2, 3 and 5-packs.

Finishing

Both need the fire-control pocket milled and the trigger, hammer and selector holes drilled. A drill press with the jig clamped square makes the pocket walls straight; a hand drill works with patience. Each lower requires its own jig; they do not swap.

Which

One build, you like the integrated trigger guard and standard buffer hardware: G150 kit. Several builds: G150 packs and one jig. Flared magwell and the Polymer80 grip design: RL556v3. Both take any mil-spec upper, lower parts kit and magazine.