I have an 870 with a 23" rifled barrel with cantelever scope mount.
I've got the same setup with a different scope that is 2-4x.
The fully rifled barrel with a scope and sabot slugs is the only way to slug hunt deer in my opinion.
My gun likes the Winchester Supreme Partition Gold 385grain Sabots.
Just a couple inches at 100 yards, and one hole at 50 from the bench.
It shoots CoreLokt Ultra that well too, but I couldn't find them one year because they had sold out. Tried the Winchesters and kept with them since I still have ammo left.
Results on deer at 125 yards...
http://www.huntingnet.com/forum/tm.aspx?m=1932396