Polymer80 80% Lower Receiver and Jig Kit (LR-308) - polymer 80
Video review
Expert review
About this product
The Polymer80 80% Lower Receiver and Jig Kit (LR-308) is a polymer-based 80% receiver set designed for building custom .308/7.62x51mm AR-style rifles. Production has been temporarily halted, making existing inventory the final available stock. This kit provides builders with the core component needed to complete a firearm while maintaining discretion in purchase and assembly.
What is the Polymer80 80% Lower Receiver and Jig Kit used for?
This kit is used for completing and customizing a .308/7.62x51mm AR-platform rifle without serialization requirements. The jig provides precise drilling guidance for the fire control group pocket and trigger pin holes, while the polymer lower receiver weighs 8.2 oz—approximately 60% lighter than our billet aluminum .308 80% Lower. Proper tooling and machining experience are necessary to complete the receiver to functional status.
How does the Polymer80 LR-308 compare to the .308 80% Lower – Billet?
The Polymer80 LR-308 is 8.2 oz versus the 20.5 oz billet version, making it significantly lighter but less rigid under heavy sustained fire. The billet aluminum lower offers superior heat resistance and longevity under high-round-count use, while the polymer version excels in weight-sensitive builds and corrosion resistance. For bench rifles or high-volume shooting, the billet option is objectively more durable.
What does it weigh and what are the dimensions?
The polymer lower receiver measures 9.2 inches in length, 2.4 inches in width, and 1.8 inches in height, with a weight of 8.2 oz. The included jig adds another 14 oz, bringing total kit weight to 22.2 oz. By comparison, a completed mil-spec forged lower typically weighs around 24 oz without additional parts.
Who is this NOT for?
This product is not for beginners without machining experience or access to a drill press. The .308 platform generates significant recoil and heat, which can accelerate wear on polymer threads and stress points. Builders expecting to fire more than 500 rounds monthly should consider the .308 80% Lower – Billet for its metal-on-metal durability and heat dissipation.
What's in the box?
The kit includes one polymer 80% lower receiver, one aluminum jig block, three drill bushings, and installation hardware. All components are packaged in a plain cardboard box with no manufacturer markings. The jig is reusable for multiple builds, though we recommend replacing drill bushings after 3-4 uses to maintain hole alignment accuracy within ±0.002 inches.
Is the Polymer80 LR-308 worth it at $100.99?
At $100.99, this kit is competitively priced for a discontinued product, offering a 22% savings over typical billet 80% lowers. The value lies in its lightweight construction and corrosion resistance, particularly for builders in humid or maritime environments as detailed in our article How PolyLock Frames Perform in Salt‑Water Environments. For those prioritizing discretion and weight reduction over extreme durability, this represents a fair cost for a functional build platform.
Specs at a glance
Pros & cons
What works
- Weighs 8.2 oz — 12.3 oz lighter than billet aluminum .308 lowers
- Jig provides ±0.002 inch hole alignment accuracy for precise drilling
- Corrosion-resistant polymer construction suitable for humid environments
Trade-offs
- No threaded insert for buffer tube — requires careful tapping to avoid stripping
- Limited heat tolerance — sustained fire beyond 120 rounds in 10 minutes risks material softening
- Discontinued product — no manufacturer support or replacement parts available
Key attributes
| Caliber | .308 Winchester / 7.62x51mm NATO |
| Frame Material | Polymer |
| Weight | 8.2 oz |
| Finish | Black |
| Completion Required | Yes |
| Jig Included | Yes |
| Pattern | DPMS |
Frequently asked questions
- Is it compatible with DPMS pattern .308 parts?
- Yes, the Polymer80 LR-308 lower is designed for DPMS pattern .308/7.62x51mm parts compatibility. It accepts standard DPMS pattern upper receivers, buffer tubes, and trigger groups. Builders should confirm compatibility with specific aftermarket components before purchase.
- Does it fit Magpul PRS Gen3 stocks?
- Yes, the receiver accepts Mil-Spec buffer tubes compatible with Magpul PRS Gen3 stocks. The stock attaches via standard carbine or rifle-length buffer systems. Ensure proper buffer weight and spring selection for .308 caliber operation.
- How long does shipping take?
- Orders typically ship within 3 business days via USPS Priority Mail, with delivery in 2-5 business days. All shipments use discrete packaging with no external markings indicating contents. Tracking is provided upon shipment confirmation.
- Can I return it if I damage it during drilling?
- No, returns are not accepted for user-damaged or completed receivers. The product is sold as-is for final machining by the customer. Ensure proper tooling and follow jig instructions precisely to avoid errors during the completion process.