The BCM M4 Upper Receiver Assembly (brand part no. 4URM4) is a multi-caliber-compatible, flat-top upper machined to correct mil-spec dimensions from 7075-T6 aluminum forgings. Bravo Company Mfg (BCM) builds in extra strength for hard use, including dropped-rifle handling and mortaring malfunction-clearance drills, then adds a mil-spec forward assist with a heat-treated tool steel pawl and a press-fit, pinned dust cover. The Mil-Std 1913 flat-top rail is ready for optics and accessories, and this semi-complete upper requires a charging handle, barrel, handguard, gas block, muzzle device, gas tube, and BCG to finish.

Key Specifications

• Multi-caliber compatible upper receiver.
• Precision machined to mil-spec dimensions from 7075-T6 forgings.
• Built for added strength under hard use and malfunction-clearance drills.
• Flat-top Mil-Std 1913 rail for optics and accessories.
• Mil-spec forward assist with a heat-treated tool steel pawl.
• Press-fit, pinned dust cover.
• Hard coat anodized finish.
• Semi-complete: requires a charging handle, barrel, handguard, gas block, muzzle device, gas tube, and BCG to finish.
• Measures approximately 9.25 inches.

Frequently Asked Questions

Is this a complete upper? No, it’s semi-complete and requires a charging handle, barrel, handguard, gas block, muzzle device, gas tube, and BCG.

What rail system does it use? A flat-top Mil-Std 1913 rail.

What is it made from? 7075-T6 aluminum forgings, hard coat anodized.

Buy the BCM M4 Upper Receiver Assembly

Start your AR-15 build on a mil-spec-correct forged upper. Order it from our AR15 uppers selection at our Lubbock, Texas gun shop, and it will ship as soon as it’s available.