The TSX and TTSX shot so well in my rifle that I never bothered to investigate further. Bear in mind that copper projectiles are a trade off. You get better penetration but usually less expansion. Occasionally expansion can be unpredictable, so the rule of thumb is to aim at bone. On the trip on which I shot the eland, I had modest expansion on two animals that lead to a fair amount of follow up even though shot placement was satisfactory. On the other hand, I had exceptional expansion at very long range when I wouldn't have expected it, and twice the exceptional penetration helped improve mediocre shot placement, including on the eland above. There's no doubt that copper is great on large animals, particularly when shooting center of mass, but I do think that you need to really pay attention when shooting smaller game, like deer.
Others make disagree, and who is to say who is right and who is wrong. These are only my personal experiences.