I've used Barnes on a good number of animals with good results. Don't believe I have had any walk away either.
As far as TTSX, I shot my 5 pt elk this year at 400 yards. Typical lung shot, he turned and ran. Since he was headed downhill i put the crosshairs above his tail and sent a second one. It hit just to the right of the spine, but put him down. 300 Wby, 180 TTSX. Also dropped a 10 year old Bison at 100 yards. Slid one just below and behind his ear. Dropped like a sack of potatoes. Nice leak hole.
I shot one other 6pt elk with a TSX at 600 yards. Two fairly quick shots, he dropped at the second shot.
I've shot a number of other animals with Barnes X and TTX bullets but no others over 300 yards.