A caveat first: All “vom Hofe Super Express” ballistics were published well before chronographs were widely available. Apparently they were established by shooting from 40” barrels over a typewriter. Noone ever came close to the advertised velocities when shooting v.Hofe factory ammo from a real rifle over a modern chronograph.
The 1931 7x73 v.Hofe SE was advertised with an 11 g = 170 gr “Torpedo Stopring” bullet at 1004 m/s = 3294 fps. The 7x73 was essentially a necked-down .300 H&H, though with a slightly larger, .3 mm, base (about the same difference as .30-06 vs. 6.5x55 SE). Due to it’s overall length the 7x73 required the use of a true commercial Mauser Magnum length action. BTW, all the known “Original v.Hofe” rifles were made for them by Christoph Funk, Suhl.
Post-WW2 Walter Gehmann aquired the “vom Hofe” name. When rifle and ammo making was allowed again in the 1950s, true Magnum length actions were unavailable. So in 1955 Gehmann simply copied a prewar experimental cartridge, the 7x66 Brenneke Maximum, and offered it as the 7x66 vom Hofe Super Express. This case is based on a .404 with a slightly rebated rim. The shorter, but fatter case has the same volume as the 7x73, but can be fitted into a slightly opened up Standard length Mauser action. Gehmann advertised it as providing he same ballistics, a 11 g bullet at 1004 m/s.
Pressure tested 7mm SE vom Hofe loads published by the DEVA don’t even get close. The fastest 170 gr loads don’t exceed 890 m/s = 2920 fps. To break the 1000 m/s within the max pressure of 4400 bar, you have to use 8 g = 123 gr or lighter bullets.