"As a matter of interest, the highest recorded velocity realized by a conventional weapon is 2,790 meters per second (9,153 feet per second), achieved in 1938 by a German experimenter named Langweiler, firing a specially-made cartridge in a reinforced 8-mm caliber barrel one meter long. The bullet weighted 0.25 gramme and the propelling charge was 11 grammes, the latter having been specially treated to increase the surface burning rate. The maximum pressure in the gun was 176,500 pounds per square inch - as a point of comparison, 40,000 lbs/in sq is about average for a modern military rifle".
From The Story of the Gun, by Hogg