I sold piles of those AV Hunter carbines back in the early '90's.

It's not a bad idea to have a pin set in the guide rib to prevent breakage of the guide rib flange and subsequent lockup of the bolt caused by the guide rib slipping forward and preventing rotation of the bolt.

I've been told it is a serious problem with .416's and a maybe-problem w/ .375's. For myself, having two of the AV Finnbears, one in .3765 and the other merely 6.5x55, I had the work done anyway.