The Modulus Arms Billet 80% Lower is machined from 7075-T6 aluminum billet stock. This is an 80% complete lower receiver requiring final machining to be operational. The raw finish has no anodizing applied.
The lower features an integrated trigger guard and flared magwell. Dimensions match Mil-Spec AR-15 patterns. Tolerances are held to ±0.003″ on critical surfaces. No fire control group or trigger pins are installed.
This lower is compatible with standard AR-15 upper receivers and parts kits. It accepts any Mil-Spec buffer tube and stock assembly. The magwell accommodates STANAG pattern magazines.
No FFL transfer is required for this 80% lower. Final machining is the responsibility of the purchaser in compliance with all applicable laws.
Jake Morrison’s shop notes
Noticed slight tooling marks near the trigger pin holes on two units—nothing structural, just cosmetic. Threads for the buffer tube were clean, no chatter, but one had a burr at the 6 o'clock position that needed a quick pass with a needle file. Jig alignment was dead-on for all three we milled.
Tested: 1216 rounds bench-cycled. Pocket tolerance measured: within 0.0005″ on this batch. Weight (actual): 14.1 oz on shop scale. Units shipped from Phoenix in April 2026: 31.
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