I shoot .300wm but I don't often go after whitetail with it. It's more along the lines of my elk rifle when I don't have my smoke pole in hand. I rarely have to shoot more than 100 yards at whitetails and .300wm at 100 is still screaming along even with a 180gr bullet. If you think your shots are going to be 300 yards and in, I would go with a round loaded up with no less than 180gr bullets that are on the strong side to avoid blow up. I reload as does everyone in my family but I try to stay current on factory loaded offerings just in case I'm out of state and my rounds didn't make it to my hunting place with me. Hornady makes a pretty great round with velocities a bit above 3100 with a 180gr interlock. That load is pretty similar to my reloads for whitetail and elk. I think it's their custom line. The interlock has always held together very well for me on the few times I have had close range shots on elk and the couple of whitetail I've taken with it. Most of my elk shots are 150-300 yards out with modern rifle but sometimes I get into under 100. But like others have said, you will need to shoot whatever shoots best from your own rifle. If you are limited to factory rounds and have no knowledge of reloading then you will have to bite the bullet and pay out the huge costs of .300wm ammo and find which one shoots best for you. Maybe you will get lucky and hornady line will be accurate for you. The newer Nosler partition bullet is pretty stout and I think there are some federal load offerings with them loaded.