I set up a dedicated deer gun a few years ago, and it has been pretty effective... Mine consists of an 870 Magum Express Deer Gun - which came from the factory with a fully rifled barrel, with rifle sights - and a monte carlo stock... I then had my receiver drilled and tapped for a Leupold QR base made for the 7600 - and bought med QR mounts, and a Leupold 2-7x33 Shotgun scope... I also added Firesights to the barrel, and had the barrel pinned - yet still removable - and some trigger work done... That way, I can take the scope off, and use the opens if conditions dictate it - and with that mounting system, it's always returned to zero... The 'smith that pinned my barrel uses a system that threads a 1/4-28 buttonhead through both the barrel and receiver, yet sits flush inside - makes the barrel/receiver connection much more rigid, and it HAS to go back to the same spot every time... This guy does factory warranty work for Remington, and really knows his stuff... Also, while in his shop, I've seen a handful of cantilever mounts that have come loose from the barrel, and were in for repair - it was on his recommendation that I picked the mounting system I ended up with - and I haven't regretted that choice for a second...
Like mike's slug gun, mine'll do an honest 1 and 1/2" group at 100 yards consistantly - which is pretty good when you consider the size of the holes, and that it's a shotgun... Mine does it's best with Federal 3" sabots, with the BarnesX bullets, though - they're pricey, but I've taken a bunch of deer with 'em... I typically run a couple of boxes through it before the season starts, and rarely have to adjust anything... Where I live, alot of the area is shotgun only, so having a good slug gun is invaluable - I've been using this set-up for 5 or 6 years now, and it's worked flawlessly...
- georgestrings