As far as I can tell .303 would have been the last black powder military cartridige ever adopted, and even then I am sure someone could still dig up another round adopted later.
The whole reason for keeping the 1882s had everything to do with cost. It was roughly a third the cost to make a 1882 over a Luger. Give the Lugers to the Infantry officers and those expected to be in combat, and the 1882s to those they felt were likely to never use it.
As mentioned reason they kept producing the 1882s and later 1929s was simply it was much cheaper to make those revolvers than to buy Lugers for everyone. Every model the Swiss adopted in the late 20s early 30s was a attempt to cheapen the cost of producing the firearms (which is fair considering they literally had their troops walking home with pretty much everything they made). M1929 Lugers and M1929 Revolver both are simplifications of the earlier models. The K31 was a cheaper design than the K11 to produce.
To the OP, as mentioned the cartridge is fairly similar to .32 S&W Long. It would also be fairly similar to .32 ACP or stronger than .25 ACP both very popular carry cartridges, and one a very popular military pistol cartridge for decades. Personally not my ideal round for 'manstopping' but all that doesn't matter if you can't hit your target in the first place.
