Paris Gun
Krupp continued theoretical research on a replacement for the Paris Gun during the Weimar Republic-era, but it was the Nazi government that finally authorized funding for experiments to solve some of its worst problems. The extremely high velocities used by the Paris Gun to attain the stratospheric heights necessary for extreme range caused enormous wear of the barrel, so much so that the shells had to be made in gradually increasing diameter to suit the rate of wear. Even then barrel life was merely 65 rounds. It is believed that the one Paris Gun destroyed by a premature detonation in the bore was caused by loading one of the serially-numbered shells out of order. Thus Krupp decided to use only eight grooves in the barrel and to machine matching ribs or splines on the shells to eliminate the need for a massive copper driving band to start the shell spinning without shearing off, which had been one of the prime causes of the excessive barrel wear in the earlier weapon. Gas sealing would be handled by a copper band, mounted in the place normally occupied by the driving band, with an asbestos and graphite packing to form the initial seal. Several test barrels, known as the 10.5 cm K 12 M, and shells were made in 1935 and were compared to a conventionally rifled barrel (the 10.5 cm K 12 MKu). The tests proved that Krupp's concept was correct.