If you don't reload get a 7mm-08. It's a 7mm bullet in a 308 hull. It's very tame on recoil but still shoots pretty flat despite how little it kicks. With a 140 grain bullet it's hot death on whitetails and although I have never hunted Mule deer I can't see why it wouldn't be just as effective on them. I have one in a Browning A-bolt and it's a great little deerslayer.

The 260 is a great caliber and definately would do the job equally well but for what ever reason the gods of gun popularity just never smiled on it. Unless you reload you may have a tough time finding a variety of ammo to choose from at most sporting goods stores and some may not have it at all. You also won't see any at the large retail stores like Wal-Mart or K-mart either. I actually wanted to buy a 260 about a year ago but had a devil of a time finding a rifle I liked chambered for it. Most of the major companies have discontinued the 260 from their line up.