The AR-15 castle nut is a crucial component of any AR15/AR10 build. The caste nut is used to secure a receiver extension (buffer tube) to the lower receiver. Made from 4140 steel and finished in a durable manganese phosphate coating for years of reliable service. A castle nut is an essential part of your next rifle or pistol build. Don’t forget to pick one up when you’re buying a new buffer tube or buffer kit to complete your next build. We also have parts kits available to help finish your build, or just to keep on hand for future use.
