Well, it's do-able, but you'll probably need to work up to those velocities. 99% of the fun of bullet casting is in the experimentation. I have run cast bullets up to about 2500 fps, that's easy enough. Running them up to 2500 fps with any accuracy will likely require some experimentation. Magnum shot, with about 3% tin added is a really good alloy, and easily heat-treatable. Heat treating is something you'll get familiar with rather quickly in your quest for high-speed cast bullets. Remember to use MAGNUM shot, not CHILLED shot. they are not the same thing Magnum shot contains antimony & arsenic, both necessary for hard cast bullets. Remember to start out with your barrels completely clean of any bullet jacket fouling before beginning, or you'll hit the wall in the first turn.
Bob