The Bushmaster M4 (brand part no. 00-20010-BLK) is a complete, built AR-15 lower receiver rated for multiple calibers and ready to accept a standard mil-spec upper. Bushmaster has supplied AR-pattern rifles and components to American shooters for decades, and this built lower keeps that same mil-spec compatibility in a ready-to-build package. Shipping fully assembled means no separate parts kit or buffer tube to source before pairing an upper. It’s a straightforward, no-frills option for builders who want a proven name behind their lower receiver.

Key Specifications

• Sold as a complete, built lower, ready to accept a standard AR-15 upper.
• Rated multi-caliber, compatible with common AR-15 chamberings.
• Includes a manual safety selector for on-safe carry between strings of fire.
• Ships at approximately 2.95 pounds, reflecting the fully built receiver assembly.
• Built to the M4 configuration in Bushmaster’s lineup.
• Fitted with a 6-position M4 collapsible stock on a mil-spec buffer tube for adjustable length of pull.
• Equipped with an A2 pistol grip and a mil-spec single-stage trigger.
• Machined from 7075 forged aluminum and sized for standard 5.56 NATO/.223 Remington uppers.

Frequently Asked Questions

Is this a stripped or complete lower? It’s a complete, built lower receiver ready to accept a standard AR-15 upper.

Does it include a safety selector? Yes, a manual safety selector is fitted standard.

Buy the Bushmaster M4 Complete Built Lower Receiver

Skip the parts-kit assembly with this ready-to-build Bushmaster lower, part of our AR15 lowers selection. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL.