Yes. I am talking about that. The velocity differences for this 4 cartridges, 7x57 vs 7x64 and 9,3x62 vs 9,3x64, in factory loads are clear, by a good margin, around 200 f/s for the common bullet weights. In hand loads with similar pressures and barrel lengths, the differences are notably smaller, also by a good margin, 100 f/s or less!
This is not theory but reality. Anticipated by theory, by the way!
I am guilty of the deviation of this thread original theme, fascinating one about the extremely rare, unknown until now, original Winchester 70 pre-64 9,3x64 Brenneke!
Would be very interesting to know more about this, and others, non-standard cartridges Win 70 pre-64 factory offerings!