Having shot far more head of big game with X bullets than you have shot total critters... AND having shot more head of big game with partitions than I have anything else, I sorta feel like I have a little clue about how they work.
I have a ton of recovered partitions, almost all have completely shed the front core. I have yet to recover an X of any iteration... And I have tried repeatedly to catch one.
The TTSX is the answer to the question I would not ask. It is a marketing ploy. As to how poorly it preformed you missed the point that an elk has some mass... deer, not so much. I did not say it was adequate preformance, but it is the only one like it I have seen pictured. And it nearly made it through the elk.
My father was a huge disadvantage for me when it came to killing stuff. He believed in shooting behind the shoulder. He knew bullets of his era could not be trusted to crunch bone and make it very far.
When I realized what an X will do it all became much simpler...
