the 300 rum is way to much gun for any deer seeing that more deer have been taken with a 30-30 than any other cal. over the past 100 yrs. shooting deer with the 300 rum is going to waste alot of meat if you hit it wrong.My thought is a 25-06 ,270 or 270 wsm,280 rem,or a 7 mag at the most if you really want a 300 mag I would get a 300 win mag it has alot less recoil then a 300 rum or 300 weatherby.Your bullet choice has just as much to do with a quick kill as the rifle size maybe even more.I found the barnes triple shock X bullet to be fantastic one most med. to med. large game, other good choices to look at are the swift line the trophy bonded bear claw, nosler accubond and partion, seirra gamekings and the hornady interbonds, try to stay away from the ballistic tips that are not bonded they sometimes break up to easy and don't pass through a you'll have little blood to follow.

Darrell