I've never messed with a .38, but I've formed a lot of .40-65 from .45-70 brass. I learned that not all brands work the same. Starline is great brass, but it's best to anneal it before forming. I really like Imperial for most sizing, but for case forming I've had better luck with pure anhydrous lanolin.
Paul
+1
I've formed some 40-65 brass from 45-70, mostly starline. Annealing before hand seems to help a lot.
