Really nice rifle Buckstyx, and a piece of history since Königsberg doesn’t exist anymore as such; a Prussian territory since long before AD 1000, East Prussia was seized in 1945 by the Soviet Union. Having the Königsberg name engraved on a rifle links you therefore to a by-gone era; I think I have also seen on the market Gewehr 98 rifles bearing the Königsberg name, as there was probably a military arsenal there prior to 1918.

The 5,6x61 SE V. Hofe (1937) delivers ballistic performances more or less similar to the 240 Weatherby Magnum (1968), with a 75-grain bullet; it is still manufactured in Germany by a company which name is Labor Für Ballistik www.lfb-munition.com ; they may have an agent in the USA from which you may get either ammunition or reloading components, and it should be worth contacting them.

Louis