I'm not sure of the dimensions of the 30/40 case, but the 30/40 cases are very weak as compared to the 444.
BTW, I have necked down and loaded 200 rounds of the 25-444. It wasn't near as bad as I thought. The key is to start with trimmed, squared up case mouths. I don't even need to use the 358 die. I first trim the brass to square up the case mouths. Then I run it through a 308 die, then the 7-08 die and then finally the 25-444 die. At this point I anneal the brass and then put them in a tumbler for a few hours to clean them up. I then run them through the 25-444ai die again, trim to length, chamfer, debur, flash hole debur, and uniform the primer pockets and then load. My plan is that once I fire form, I will anneal one more time.
Now I just have to wait for the barrel to get here!