If you didn't have any problems with the nickle-plated cases, you won't have any problems with regular brass.
Like yorke said, I've made some 338-06 cases out of 25-06 that have 5 firings so far, with only one split neck. Also, have some 30-06 that are now .270, vice versa; 30-06 that are now 25-06, .270 that are now 338-06, just because I wanted to see if it could be done.
The only difference between all these cases and your situation, is the shoulders are in the same place, and it sounds like there is some difference in the 300 and 325 necks/shoulders.
I've tried to make .222 Rem out of .223 Rem without success due to the different shoulders. Tried to make .243 Win out of .308 Win without success due to the drastic step-down in sizes without using a die calibered in something in between those two. Just ended up with some crushed cases and whatnot. No big deal because it was fun to try experimenting.