i would not recomend drilling and taping the barrel for a scope....if my memory is correct the plug is about a inch and ahalf long????the barrel is thin at this part,,<where the rear hole WOULD BE>in the base.....i dont have a old one any more to look at to make sure of my answer...but a h&r with a push in plugs wont be worth the money to drill and tap it to me because there are better <huntsmans,sidekicks> and SAFER GUNSTHAN A PUSH IN BREECH PLUG.......you do know all the warnings of the push in plugs????jb