The mention of a 7x75R vom Hofe Super Express rang a bell in the back of my head! About 20 years ago I was shown a Kipplauf, single shot break open rifle chambered for this cartridge that had developed some shake after about 100 shots. It was made about 1960 by a no-name (I know the name) gunmaker in Wildflecken, Germany. It was a very primitive design from the start, looking quite good outside. Inside, it was a single-bite design, without any top fastener or dolls head. To make things even worse: Though the bite in the barrel lump was of quite generous dimensions, about 10 mm wide and 8mm deep, the workmanship was lousy from the start. The locking wedge was much to short, going over the edge of the of that bite for only about 1 mm. Of course, though the rifle had stood proof, this lockup surface of about 10 mm x 1 mm was insufficient. I would not have trusted such a break-open rifle design for more than a .22 Hornet or a .30-30, let alone the lousy execution with the too short single-bite locking wedge. Many US troops were/are stationed in Wildflecken, so I guess that gunmaker sold some-many of his fine-looking break-open stalking rifles to unknowing GIs. In such rifles anything above a .22 lr would be a killer!