Over the years I've experimented with a lot of X bullets. They all gave me plenty of reason to complain. That is until the TSX bullets arrived. The TSX has been relatively easy to get to shoot well in several of my rifles and definately leaves less copper in the bore.
They still get copper fouled but not as heavily. If you plan on shooting X bullets I'd suggest buying a bottle of Barnes CR-10. They go hand in hand.
By the way, I have shot many whitetails with the X bullets. I get total penetration but don't consider them to be "too much for deer". Some guys like them because you can eat right up to the bullet hole - so to speak.
VH