Generally, you should look at the bullet in terms of speed over a determined distance such as 100 yards. Most magnum loadings with jacketed bullets and the slow burning powders made for them don't allow very much variance in powder charge. So muzzle speed isn't going to vary a whole lot without changing powders, pistols etc. The last XTP'S I bought in .38 cal had a little paper inside stating the speed range. They are designed for a wide range of speeds. For the life of me, in all the years I've been on various boards etc, I can't ever remember anyone complaining about XTP bullet performance (other than self defense because of over penetration).
There are three kinds of men:
1) The ones that learn by reading.
2) The few who learn by observation.
3) The rest of them have to pee on the electric fence and find out for themselves..........