Nicht Für Kugel, Nem Golyonak, Jen Pro Broky just notes constriction and is comparable to Crown over W. In the Austro-Hungarian empire during preliminary proof there was no distinction between smoothbore & rifled tubes as both were fed ball or cylinder, with an allowed clearance of up to 0.5mm. Then all tubes were exposed to some 10 ATM test with a pump apparatus to check for failures. Next rifled tubes were fed a diet of 2 balls or cylinders, what better way to double the weight, while scattergun tubes received a load of 1 1/2 times their shot charge. Most sources give the 1st & 2nd proof for scatterguns was with a solid projectile while the 3rd proof, which could also be an inspection, was with shot. On a tube with choke the diameter was measured forward of the chamber while cylinder tubes had their diameter measured at the muzzle.
I'm not sure why early German scatterguns were so stamped unless they were destined for the Austro-Hungarian empire.
Kind Regards,
Raimey
rse