I've shot a shit load of Tannerite but never with a muzzleloader. I have shot muzzleloaders over a chronograph. Even shooting a round ball in a fifty I don't think I ever quite made 2000 fps, although you can come pretty close. Maybe a long barrelled squirrel rifle could pull it off. Or maybe you could push a real light sabot up to 2000.
8-track, gun rack, spittoon, gimbal mounted beer buoy, blah, blah, blah, blah......