TacFire MAR039 Castle Nut Black Steel for AR-15 Buffer Tube

The TacFire MAR039 Castle Nut is a mil-spec locking nut designed to secure an AR-15 buffer tube to the lower receiver. Manufactured from durable steel with a black finish, this castle nut threads onto the buffer tube and is staked in place to lock the carbine stock assembly firmly and reliably onto the lower.

Compatible with standard AR-15 platforms chambered in .223 Remington / 5.56x45mm NATO, the MAR039 is an essential component for any lower receiver build, repair, or restock. Its mil-spec dimensions and quality steel construction ensure reliable fitment and long service life under hard use, whether you are completing a new build or replacing a stripped or damaged nut during routine maintenance.