Stephen,
Regarding the "sweep" of the case, I just figured that was the way I would do it if I had a 9.3x57R reamer already. I don't recall the approximate time the standardization was done but it was considerably before 1939. That standardization was a matter of agreement between interested parties (I don't know who they were but believe they were representives of ammo and gun manufactures and maybe hunting organizations), but the 1939 law was enforceable as a matter of law. The loads would use propellants appropriate for Proof of the gun. I don't use black powder in my guns, but 4198 is often used in NFB loads, Nitro Proofed guns could use 3031 or 4895 or similar powders very well, and Express Proofed guns could use the same powders but with different loads. Express loads are a little heavier than "nitro" but are by no means magnum level. The typical 193 grain bullet for the 9.3x72R are not only made to be safe for use in varying diameter barrels but the jackets are also made for the velocities expected. I returned from Germany with a quantity of RWS bullets, and I believe they are still made. I "fell into" a deal for some Z&B bullets for this cartridge and am sure they are still made. Since they have a "US presence now" I hope demand will be enough that they will market these and other bullets (.318"?) here. Norma has also produced these bullets in the past. I have not tried the Buffalo Arms bullets, but they look like they are re-formed from 200gr .358" RN bullets and should work fine. Members of this forum have used the 200 grain Hawk bullet made for the 9.3x72R and report satisfaction. Bullets made for 35 Remington and jacketed .38/.357(also new .350 legend, etc.) will work for those rifles with .358-.359" groove diameters. There are a lot of cast bullets that can be used without breaking the bank. The Lyman .366408 was traditional 9.3 bullet, but I'm not sure if the mold is still available, and when it was, to use it in more modern rifles required the blocks to be shortened to drop bullets of about 200 grains. Jacketed 9.3 bullets made for more powerful cartridges such as 9.3 x62/64/74R or even 57 shouldn't be used even if the barrel has .366" groove diameter.
Mike