todbartell,
First of all, why would you be using a TSX for a long-range bullet? It's about there is for a high-velocity, close-to-medium range bullet, but not at all for long range. I've worked up 2 loads in my hunting rifles, each of which have matching POI's between the 2 loads. I load a TSX/TTSX for 400 yards and under, and something like an A-Max or a Berger or a MK for over 400 yards.
I'm not sure where you're getting your numbers, once again, but I get significantly different ouputs in JBM. When put the 115gr TSX at 3100fps vs. the 120gr TTSX at standard atmosphere, at sea level, with 10mph crosswind, 200 yard zero for both, I get 6.8" of drift for the .25-06 and 12.2" for the .260 at 400 yards. The 120gr PT drift 7.9", and the 125gr PT 12.4" at 400 yards.
I'm not concerned with bullet drop or RE whatsoever. I'm simply concerned with the bullet having sufficient velocity upon impact for expansion, and the old devil called the wind.
.25-06 wins every time, BUT it burns more powder doing so.