Well, it's been a long while since I've posted, but I think I finally resolved my issue.
It seems I don't have any hope of ever getting 30 grain to load. I did make an adjustment to the 25 grain cartridge: I was using the nitrated paper from Buffalo Arms, which looked like it was plain ol' 8.5 x 11" printer paper. So I decided to make my own paper by nitrating some coffee filters.
EUREKA. I had 24 cartridges made up, and no problems loading at all. So it seems the paper I was using was simply WAY too thick for the purpose.
So beware of the nitrated paper from Buffalo Arms. That stuff is probably WAY too thick.
Now I just need to make up a whole bunch of cartridges for another range day.