The AR-15 has always been constructed from good ole’ metal alloys: 4140 steel, 416R stainless, 6061 billet, and 7075 forged aluminum – all have contributed to the black rifle’s reputation for being reliable and battle-ready. But new build options have hit the 80 lower shelf with radical designs that promise to improve on the O.G. ArmaLite blueprint. The latest entrant grabbing attention is made from weapons-grade polymer, promising some unique benefits. So, is an 80 lower made of “plastic” any good? Let’s look:
The G150 Phoenix Polymer 80% Lower
Our friends over at Polymer80 – the same guys who brought us the 80% pistol kits – have introduced the first polymer lower with the G150 Phoenix. The Phoenix lower offers black rifle builders the opportunity to piece together an ultra-light AR-15 by using a polymer stripped receiver instead of a billet or forged unit.
Polymer has played a big role in making lightweight (but durable) handguns and submachine guns. But can it stand up to the extra abuse of a supersonic rifle round and a direct-impingement gas system?
Can a polymer 80 lower stand up to rifle rounds?
Yes. Polymer has been toyed with and tested in the AR world before, with some not-so-successful results. The G150’s designers took previous examples’ failures into consideration. Most commonly, the buffer tube housing or pistol grip mounting area would fail during firing. Obviously, that’s quite dangerous. So, designers beefed up the G150 and used a different formula for the polymer itself.
Many builders have already completed 5.56- and .223-chambered (and even LR-308) rifles and pistols with the G150 Phoenix. They’ve reported reliable functionality with no failures or safety issues.
This isn’t surprising, considering the testing and work Polymer80 put into the Phoenix. After a round of initial testing (which was successful), the engineers bolstered the G150’s overall integrity and stiffness by 15%.
The G150 Phoenix also incorporates a solid core design. Essentially, they took the same material used to build pistols and polymer weapons and made it better-suited for rifle rounds. Lastly, they reinforced the magwell and buffer tube housing (which is mil-spec).
Want an ultra-light AR-15? Polymer wins
The obvious advantage of a polymer lower is weight. The G150 Phoenix graces the scales at around 0.3 pounds. With a standard lower parts kit installed, total weight comes in at just over 1 pound.
Compared to a forged 80 lower with a comparable parts kit (which weighs around 2.15 pounds), that’s a 50% weight reduction. More importantly, that weight reduction occurs at the weapon’s center of gravity.
This means you’re shaving some noticeable weight while enjoying a nice, balanced rifle (or pistol) that still uses a conventional upper receiver out front and regular buffer system out back.
Polymer 80 lowers include their own jig
Besides weight, there’s another big reason to consider a polymer lower for your AR-15 build: It costs a lot less than other build options. Whereas forged or billet 80 lowers are sold separately (minus in combo kits, of course), the G150 Phoenix includes its own 80 lower jig.
This means you’re getting an automatic 2-for-1 deal and saving a nice chunk of change that would otherwise be spent on a jig. With the AR-15 version of the polymer lower selling under $100 — and with most jigs costing at least $190 or more — you can see the savings you get on the gunsmithing and tool part of this project.
Machining polymer is easier, too
Finally, build difficulty. Or in this case, build advantages. If you’re new to gunsmithing or you’re worried about not being able to pull off your first AR-15 build, a polymer lower’s a great choice. Polymer is an incredibly dense material that is still easily workable – more so than forged or billet aluminum.
The polymer 80 lower also comes with the drill bits and tooling you need to finish it:
- Set Screw Bolt Catch Pin
- Dowel Pin for Bolt Catch
- Pistol Grip Nut
- Pistol Grip Screw
- Allen Wrench
- 7/16” End Mill Bit (depth-marked for fire control pocket)
- 5/16” Drill Bit (trigger pin hole)
- 3/8” Drill Bit (safety selector switch hole)
All you need to finish a polymer 80 lower is a Dremel and hand drill. Forged and billet 80 lowers require the use of a handheld router and, in some cases, a drill press. So, sticking with polymer saves you some cash on tools, too.
Yes, polymer 80 lowers are quite good. Our customers have loved them for quite a few reasons: They’re more affordable than metal lowers and jigs. They’re easier to machine and build with. They’re capable of taking some real abuse, as any good AR should. If you want to build an ultra-light rifle or pistol, a polymer 80 lower is the secret. Now get to building!