I agree with unclenorby and it isn't just because we're both uncles. Ha ha

The cantilever slug barrels are a big step over any saddle type or similar scope mount you would put on the receiver.

Food for thought.....you don't see the rear sight on the receiver now - the sights are all a part if the barrel.

Shooting slugs out of a pump shotgun really delivers a wallop of a kick a lot more than any birdshot. I've seen lots of guys barrels become loose and they wind up with very poor accuracy from their saddle mounted scopes. When you fit a call or semi auto shotgun with different barrels you'll never get the tight fit that a rifle has their barrel fitted into the receiver.

I would recommend looking into a cantilever barrel Mossberg make some really nice ones you could probably get into one for about 200 bucks.