Just about any powder with a burning rate similar to IMR-4895 will do well in the .358. Some of my favorites are A-2460, A-2520, RL-15, etc.. It important to stay below maximum loads in the 99 action. The rear locking action is not as strong as some of the bull tough compact bolt actions. Not worth risking damage to your gun for a few more feet per second. I imagine that parts are scarce, and not cheap. That being said, the 99 is a handy smack down rifle, and carries easily in tough terrain. Your 200 gr. Hornadys will give a good account of themselves at .358 Win. velocities. It is one of my favorite bullets in the .358 JDJ, which has similar ballistics.