Hello all, after six years of surgical and other medical procedures and my most recent I had a complete shoulder replacement which over more time I maybe able to use my Mossberg 600at, in anticipation of the ability to use it again I purchased a utg low profile pictinny/weaver scope mount for a red dot scope. A situation has come to my attention after all these years I got the shotgun out which according to the mount with screws are the same size as factory holes, my problem is my shotgun does not have factory drill and tapped holes! If anybody can tell me what the drill size and tap size along with thread count, so I can drill and tap myself :shock: thank you if somebody can help with my Delma.