You know, as long as you hit the paper where you want it. From my personal experience with these (factory chambered, I did not try the rechambered ones, yet) you may expect a fair 2300 fps with some good accuracy with the 649 models. But yes, you will need the chrony.... just to confirm the speed and tune your load in accordance to what you want. You usually will find you're more of less 100-150 fps slower than what you expected with a given load. Faster powders, in the RL15 class will provide the best results.
I also shoot recent-made 9.3X62 rifles and they have much shorter leade and tighter barrels, so they usually give more velocity.