Well in that case a rifled barrel might help you. Or maybe change your blind location or alter the way you hunt. Hard to say without knowing why the deer will not come closer, but 80 yards should be doable with a good rifled barrel and the proper ammo.

As far as what to use, you really need to play to see what your gun likes. The bad thing is it gets expensive, especially with sabot type slugs.

My H&R ultra actually shoots really well with the Winchester rifled slugs. Fouls up the barrel something awful after 3 or 4 shots, but they group around 1-2 inches at 100 yards for the first two or three shots.

80 yards is pushing it for a smoothbore though, some guns can do it, most can't.

I have two buddies, one uses an 870 and the other an 11-87. Both with cantilever barrels. There guns shoot pretty well with winchester super X sabots. I would also give lightfields a try and some of the newer pistol bullet type rounds. Like federal barnes expanders, remington copper solids and the winchester platinums. You could try some of the faster offerings, but I wouldn't get your hopes up. It seems to be hit and miss for accuracy in guns with slower twist rates, which most rifled shotgun barrels are.

Paul