The Luth-AR Carbine Lock Ring / Castle Nut is a straightforward, duty-ready component designed to keep your AR-pattern carbine solid and secure. Machined from robust 4140 steel and finished in a protective manganese phosphate coating, this castle nut provides dependable retention for your carbine buffer tube, helping maintain a consistent, stable interface between the receiver extension and lower receiver over years of use.

Ideal for new builds or refreshing a well-used rifle, this lock ring works with commercial, mil-spec, and hybrid buffer tubes on AR-15 and AR-10 style carbines. Its clean threading and durable finish make installation simple and reliable, whether you are assembling a range rifle, training carbine, or general-purpose AR. Backed by Luth-AR’s reputation for precise manufacturing and long-term reliability, it is a small part that supports consistent performance.

Key Features:

• Manufacturer: Luth-AR
• Model: CS-02 Carbine Lock Ring / Castle Nut
• Material: 4140 steel
• Finish: Manganese phosphate
• Compatibility: AR-15 and AR-10 carbine buffer tubes; works with commercial, mil-spec, and hybrid extensions
• Function: Threaded steel ring used to retain the carbine buffer tube to the lower receiver