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 non-serialized polymer firearm component requiring user completion for AR-10 platform builds. It ships with a precise jig for drilling and milling operations. Production has been halted, making remaining stock limited.
What is the Polymer80 80% Lower Receiver and Jig Kit used for?
This kit is used to build a custom AR-10 lower receiver without serialization. It requires drilling three 5 mm holes and milling internal cavities with a router. The jig ensures proper alignment for fire control group installation.
How does the Polymer80 LR-308 kit compare to the .308 80% Lower – Billet?
The Polymer80 polymer kit weighs 340 grams and costs $100.99, while the .308 80% Lower – Billet is aluminum at 480 grams and $189. The billet is more durable for high-round counts, but the polymer saves 140 grams and $88.
What does it weigh and what are the dimensions?
The lower receiver blank weighs 340 grams and measures 220 mm long, 50 mm wide, and 90 mm tall. The jig adds 720 grams, with overall kit dimensions fitting a 300 mm x 150 mm work area.
Who is this NOT for?
This is not for users seeking a finished, serialized receiver or those in states prohibiting 80% builds. It requires tools like a drill press and router, taking approximately 2 hours to complete. Beginners should review the Best Drill Bits for Polymer Frame Modifications first.
What's in the box?
The box contains one polymer 80% lower receiver blank, one aluminum jig, three drill bushings, and six mounting screws. No tools or instructions are included; refer to online resources for milling guidance.
Is the Polymer80 LR-308 kit worth it at $100.99?
At $100.99, it is worth it for builders prioritizing weight savings and cost over metal durability. Compared to a finished lower at $250+, it offers legal customization. However, polymer wears faster than aluminum under sustained fire.
Specs at a glance
Pros & cons
What works
- Weighs 340 grams — 140 grams lighter than the .308 80% Lower – Billet
- Includes precision jig with 0.1 mm tolerance bushings
- Costs $100.99 — $88 less than aluminum billet alternative
Trade-offs
- Polymer construction — less durable than aluminum under sustained fire
- No included tools — requires drill press and router
- Limited availability — production halted, no future restocks
Key attributes
| Caliber | .308 Winchester |
| Material | Polymer |
| Weight | 340 g |
| Length | 220 mm |
| Width | 50 mm |
| Height | 90 mm |
| Condition | Unfinished |
| Platform | AR-10/ LR-308 |
Frequently asked questions
- Is it compatible with DPMS pattern parts?
- Yes, it accepts DPMS pattern fire control groups, buffers, and stocks. Use standard AR-10 parts kits; avoid Armalite spec components to ensure fit.
- Does it fit Mil-Spec triggers?
- Yes, it accommodates Mil-Spec AR-10 triggers and hammers. Test fit with a known brand like Geissele or LaRue for optimal function.
- How long does shipping take?
- Shipping takes 5-7 business days within the continental US. Expedited options are not available due to compliance checks.
- Can I return it if I damage it during milling?
- No, returns are not accepted for user-damaged items. The kit is sold as-is; practice on scrap polymer first to avoid errors.