I think the 25-06 is a great caliber and would be quite fine for mule deer. My only problem with the 25-06 is that there is not much bullet weight, so you don't really want to lose any of the bullet due to fragmentation at all or else you will lose your penetration. Because of this I recommend using some type of premium constructed bullet along the lines of the Nosler Partition, Nosler Accubond, Barnes Triple Shock or well you get the idea.