i have a beretta 302 12 gauge shotgun. im going to buy a slug barrel for it and want to put a scope on the gun, but i dont want to have the scope mount permanent , like drilling and tapping the receiver ,  is there any other scope mounts that are removable for the beretta shotgun? thanks. 

You may have an easier time searching around for a rifled cantilever slug barrel.  Barrels for the Browning B-80, Beretta AL, 300, 301, 302, 303 will all interchange, so remember that in your search. I believe Hastings made a cantilever barrel for the Beretta.