A female hunter, with five witnesses, shot a sizable running Mulie buck, 5 times in a pie plate sized group, at 200 yards with a .243... she was an awesome shooter... The buck ran 200 yards before it fell.
I hate to be a skeptic but im not buyin that unless you were one of those five witnesses. I shot four deer with the .243 and my brother took two when i had one. Every deer except one that i gutshot dropped within 50 yards of a single hit from a 100gr Nosler Partition. My longest shot was about 200 yards and the closest was made by my brother at about 40.
In my opinion the .243 is definetly adequate for Mulies you just have to select your shots. I've seen deer shot with 7.62X39, .243, .303 Brit, .30-06, .270 Winchester and 7mm Magnum. As far as i know the deer cant tell who has the bigger gun if you put the bullet into its heart or lungs (with the possible exception of 7.62X39mm which IMHO isnt a deer round).