i had a 20'' 870 with rifled sights, and using winchester 2 3/4'' rifled slugs i hit a phonebook a couple of times at 150 yards. Won $20 from a guy telling me the slug wouldnt penetrate.
bones1744 was at the range that day with a friend of his, and his buddy repeated it with a 870 marine magnum with a bead sight. I couldnt do it with the bead.
i took us both a couple of trys to get the trajectory down at that range, and we ended up having to hold about 16'' high, but after that we got fairly good at it. Both shotguns were smooth, not rifled. And we were shooting from a bench.