I guess since everyone is giving their favourite and reasoning why their cartridge is the best all around for deer hunting out west I don't have to sit on the fence and say "pick one that fits your distance, energy, and recoil tolerance because there are just too many to say best all around that fit the bill."
So that being said; in my opinion the best all around factory loading for western mule deer and whitetail is a 6.5-300 Wby Mag shooting 127 Barnes LRX!
Zeroed at 300 yards it's a point and shoot rifle out to 400 yards with it 2.5" high at 100 yards, 2.8" high at 200, and 7" low at 400 yards. It's also got 1800 ft-lbs at 500 yards still and only 19" drop. No lead in your meat, and the deer drops like a stone in place when that bullet zips on through like lightning. It's expensive at $120-$140 per box (unless you reload, but you said factory) but it can be found in more places than you'd think you would as it's the second most popular Weatherby cartridge (last I checked) behind the 300 Wby. It's inefficient and expensive but it works better than I ever expected and with a muzzle break on it, the recoil is softer than a 308. You'll have confidence in your shot if you place it in the boiler room! Heck, you can use it on moose, elk, deer, black bears,and pronghorn, everything you can hunt out west!
, 300 RUM
