Josh.... Any factory load will kill deer well in the .300 Winny, but as James says, a stout 180 grain bullet will do less meat damage...150 grainers in the .300 mags are notorious for ripping up a lot of eating meat...If you shoot 'em in the ribs, it really doesn't matter much, I guess...

You mentioned that you might have shooting opportunities as long as nearly 300 yards..With that in mind, I'd suggest that sighting in at 50 yards is kind of a waste of your rifle's flat trajectory...Sight in about 3 inches high at 100 and you can use a center chest hold all the way outto 300 yards or somewhat farther....