I have an AR DMR that is semi-only and fires at 495-497 fps with 0.25g. Needless to say, I can't use it anywhere except my home field, and it will sting you pretty good at ranges of 150' no problem.
But to operate at those velocities reliably required an investment outside the scope of what you're planning, by a long shot. It's not much help for your project, but just giving you an idea of where it can go, and the possibilites.