The CMMG Mil-Spec Barrel Nut (part no. 55DA296) is a direct-fit replacement for the nut that clamps your AR-15 barrel to the upper receiver, built to the same mil-spec dimensions as a factory nut. CMMG machines it from 8620 steel and finishes it in phosphate for corrosion resistance and a proper mil-spec look under a handguard. Whether you’re swapping barrels, rebuilding an upper, or replacing a nut that’s been rounded off by the wrong wrench, this is a straightforward drop-in part sized for the standard AR-15 platform.

Key Specifications

• Made from 8620 steel for strength at a high-torque connection point.
• Finished in phosphate for corrosion resistance and a mil-spec appearance.
• Built to mil-spec dimensions for standard AR-15 upper receivers.
• Functions as a barrel nut, clamping the barrel to the upper receiver.
• Ships at 0.095 lb, adding almost nothing to your order.

Frequently Asked Questions

What does a barrel nut do? It clamps the barrel extension into the upper receiver, holding headspace and barrel alignment.

What is this nut made of? 8620 steel with a phosphate finish.

Buy the CMMG Mil-Spec AR-15 Barrel Nut

A rounded-off or damaged barrel nut turns a routine barrel swap into a fight, and this CMMG nut is a mil-spec replacement that installs the way the factory part should. Order it from our Lubbock, Texas gun shop and it ships fast to your door, along with more small AR-15 parts.