I only have two things to add, as I’ve only killed paper with cast in a rifle.
First, since your rifle has the 31 cal bore, do you know how much free bore there is? Who’s to say it’s to print since bore is not “standard”. Maybe it HAS enough free bore to allow way more bullet out of the case. Same as to what works through the magazine, you didn’t state it WAS a short action rifle. If it’s a long action you could potentially use an even heavier bullet (only speaking to mag length, not twist issues etc).
I think you’ve left out some important info to take into consideration of what your “outer limits” actually are.
Random thoughts from this random guy on the interwebs.
.
BTW thanks to all that shared what’s worked for them at the bench and in the fields.
Been thinking I should get a mold and start shooting my Swiss K31 again, going to research what designs work well with its chamber etc.