Bolt Shroud
The rear cap of the bolt that encloses the firing pin assembly and helps contain escaping gas if a primer or case fails.
The bolt shroud is the cap that closes off the back of the bolt body, surrounding the firing-pin spring and striker assembly inside. Beyond holding those parts in place, it serves a safety role: if a primer pierces or a case head ruptures, the shroud helps redirect high-pressure gas away from the shooter’s face rather than letting it vent straight back.
On many actions the shroud also carries a cocking indicator and frames the cocking-piece at the rear of the striker. A well-fitted shroud, paired with a properly sealed bolt-face, is part of why a modern bolt gun contains a failed round so safely.