I've been trying to learn more about this fascinating piece of history, and something I haven't been able to figure out is what prevents rim lock. I don't see an interrupter like the Mosin Nagant or a large angle in the magazine like the Lee Enfield.
Theories I've seen included:
Cartridges have a rebated rim, which at least doesn't seem to be the case with 30 40
The rims are beveled, but given the massive sporterization, it seems unlikely that it would continue to work in so many different calibers.
There's a guide, in the exploded parts diagram I looked at, I didn't see anything that would act as a guide.