These were made in many cartridges up to .600 NE .
Correct.
In 600 NE and in 577 NE and in 500 NE (even in different 500 wildcats calibers, custom made directly from the factory - then in Münnerstadt/Germany -).
 ....when got back swopped it for 2 other rifles with Paul...another problem was the new 500 NE ammunition back then had a small groove around the base of the case where it joined the rim. So when loaded in the magazine with each rim in front of the one below it the rim hooked into the groove and stuck there, so you couldn't move the bolt forward and chamber a round...I had some old kynoch so loaded those first then a new one last, as the older kynoch didn't have the groove...
 ....when got back swopped it for 2 other rifles with Paul...another problem was the new 500 NE ammunition back then had a small groove around the base of the case where it joined the rim. So when loaded in the magazine with each rim in front of the one below it the rim hooked into the groove and stuck there, so you couldn't move the bolt forward and chamber a round...I had some old kynoch so loaded those first then a new one last, as the older kynoch didn't have the groove...