Got a barely fired Ruger Gunsite Scout for a steal off of gunbroker. Only had the chance to take it out once. Just now fitting it with a new scope and noticed what looks like an empty screw hole at the back of the receiver at the end of the bolt (pic attached). Is this indeed missing a screw? Cant find any images online that have a clear view and obviously want to replace it if so before I shoot it again! Thanks in advance!