first, forget COTW when it comes to old German cartridges! It is incomplete and inaccurate.
There was not only one 9.3x72R case, but at least five! The 9.3x72 Sauer & Sohn is easily dismissed, as it is of bottleneck shape, essentially a sligtly shorter 9.3x74R. Then there was the 9.3x72R D = Deutsche = German shape. This had a rapid taper from the base for about 1" and then was straight to the mouth. Apparently you have a D chamber. Next we had the 9.3x72R E = English. this one had a very slightly smaller base diameter than the D, but a straight taper to the mouth. Then the rare 9.3x72R Nimrod with a shape similar the E, but a smaller rim. About 1905 the German gun and ammo companies agreed to create the fifth, the 9.3x72R N = Normalised, designed so that all the older chambers could be easily rechambered to the new standard design. Of course, all "modern" post-WW2 loads by both RWS and S&B are of the Normalized type. Normalized cartridges usually do not enter tight D chambers for the same reason you describe.
To add to the confusion, there also were 9.3 x70R D and E shapes, a 9.3x75R Nimrod with a slightly larger base, and then three 9.3x82Rs again!
