I believe it is the threaded barrel protector. If you decide to remove the muzzle brake, you put that on to protect the threads from damage. As my ol' man used to tell me: "The only stupid question is the one not asked."
I believe it is the threaded barrel protector. If you decide to remove the muzzle brake, you put that on to protect the threads from damage. As my ol' man used to tell me: "The only stupid question is the one not asked."