I bought a bunch of 378 Weatherby headstamped brass that someone had necked down to 30-378 Weatherby. I would like to change them back to 378 Weatherby. I've tried the press route and even with a lot of lube, I end up collapsing the shoulders on some of the cases.

I'm thinking fire forming might be faster and result in less loss of cases. I'm considering a load of Blue Dot under cornmeal or some such thing but, if someone has traveled this road before and has some good advice, please let me know.