The Smith Enterprise Tactical Extended Bolt Stop is now machined from bar stock and case hardened and has limited civilian availability. A must for high stress or cold weather applications. Standard issue on USN & USAF MK14's and US Army M14SE's. Current design does not allow the bolt to close with an empty magazine inserted (but it can be closed if the magazine follower is pressed down).NoteThe extended bolt stop/release is designed to make access and manipulation of the bolt much easier and faster. Therefore, do not rest the weapon on its side or leave it unattended if the bolt is locked back and a loaded magazine is in the receiver. always keep the safety engaged.