Keith is right on, see the difference in the H&R bases and the Weaver #82 base below, the middle base is the Ultra rail, just used with huge scopes. Although you can easily cut cross slots in the Weaver #82, it has a flat spot on the rear 1" of the rail that puts the rear slot even with the second slot forward on the H&R rails.
Objective size makes little difference, there's plenty of room for a 50mm scope in medium Burris rings IF the power ring/ocular bell doesn't iinterfere with the hammer. The pic is a 6.5-20x50 Simmons WTC18 on a Handi-rifle, there's about 1/8" clearance at the hammer and AO, definately needs a hammer extension!
Tim