I have been doing some research on the maximum velocity of conventional powder propelled projectiles. In general the maximum seems to be in the vicinity of 12000 ft/sec (3660 m/s for you Imperial challenged).
To confirm some research I am looking for a paper:. Heiser, R. Gasdynamic Limits of Maximum Attainable Muzzle Velocities for Conventional Guns. 5th International Symposium on Ballistics, Toulouse, France, 1980
Can anyone help.