I don't hunt deer with guns, but I'm partial to my Remington 700 varmint chambered in 22-250 when I feel like rolling up a yote!
.300 win mag w/165gr Hornady SSTs will absolutely turn the insides of a whitetails' chest cavity into a bowl of spaghetti. The level of soft tissue trauma is astounding and freakishly deadly. Never had one go more than 8 yards; and that was mostly straight sideways due to the sledgehammer to the ribs. I use that in open country. And no, I don't worry about ruining the meat since I try to avoid the shoulder. Just get it in their rib cage and they will drop. I carry a .450 Bushmaster with 250gr FXTs for swamps and thickets. Haven't loosed one of those at a deer yet but hope to rectify that this year. Those are nice guns and only kick about as hard as a 20 ga shotgun.
Make sure you check point of aim with your O/U before deciding to rely on it for slug shooting. I once had the idea that since African professional hunters use short heavy caliber double rifles for stopping dangerous game, that a nice handling little 26" barrel Ithaca/SKB 12 gauge side by side double shotgun I had should make a very fast handling hard hitting brush gun for stopping deer. In theory it sounded reasonable until I hit the range. Both slugs converged to about 45 yards but after that they crossed paths with the right barrel shooting well left and the left barrel going wide right at 75 yards. The shotgun being regulated to throw a shot charge together out to 40-ish yards caused the solid slugs to cross and at 75 yards they were 16" apart (from memory) with nothing in the middle at the bullseye! Evidently those African big bore double rifles are regulated differently than double barrel shotguns are! My SxS went wide horizontally, I don't know but an O/U might do the same thing vertically? It would be necessary to check that out I think based on my one experiment.
I have the 50. cal T/C Encore with Mahogany stock and the 45. cal CVA Kodiak Pro Magnum. I have an Ithaca 12 gauge. We shoot deer every year with that thing at 150yds. The shotgun is amazing.
