Daveinthebush brings up a valid concern. With the cantilever barrels, the scope is mounted to the barrel in the hope that if the barrel moves the scope will continue to track right along with the barrel. Problem is that the cantilever can be pushed or bent, knocking the scope out of alignment.
The receiver mounted scope is stronger, but if the non-cantilevered barrel was to be removed and remounted after sighting in, then you have to sight the gun in again (theoretically, at least). With pump guns, it is wise to clean the barrel before sighting-in, tighten down the barrel screw securly, and leave it on till after hunting season is finished. Both designs have positives and negatives. :roll:
Jim