Sig Sauer M400 / 516 Stripped Lower Receiver, 5 Pack

About this product

# Sig Sauer M400 / 516 Stripped Lower Receiver, 5 Pack ## Build with Confidence – OEM-Grade Foundations Every serious AR-15 build starts with a stripped lower receiver that balances precision machining with rugged reliability. This 5-pack of Sig Sauer M400/516-compatible lowers gives builders and shops a cost-effective foundation for multiple projects without compromising on material integrity. Machined from 7075-T6 aluminum and hardcoat anodized, these receivers meet the same dimensional standards as factory Sig Sauer components. Ideal for bulk builds, backup inventory, or custom shop work. ### Key Specifications - **Material:** 7075-T6 aluminum (aircraft-grade) - **Finish:** Type III hardcoat anodized (matte black) - **Compatibility:** Sig Sauer M400, 516, and most mil-spec AR-15 parts kits - **Fire Control Group Pocket:** Auto-sear ready (M16 cut) - **Threaded Bolt Catch Pin:** Secures without drift punches - **Markings:** Clean, unbranded design for custom engraving - **Includes:** 5x stripped lower receivers (no small parts included) ## Feature Breakdown **Precision Machining for Tight Tolerances** CNC-milled from forged 7075-T6 aluminum, these lowers maintain consistent wall thickness around critical stress points like the buffer tube threads and takedown pin holes. The threaded bolt catch pin simplifies assembly compared to traditional roll-pin designs, reducing marring during installation. Tighter-than-average magwell dimensions ensure minimal wobble with PMAGs and USGI magazines. **Anodizing That Stands Up to Hard Use** The Type III hardcoat finish exceeds standard anodizing for abrasion resistance, particularly where the safety selector and trigger pins rotate under repeated use. Unlike cheaper finishes that wear to bare aluminum around high-friction areas, this retains corrosion protection even after thousands of cycles. Matte black provides a neutral base for Cerakote or other custom coatings. **Compatibility Without Compromise** While optimized for Sig