I just made one for my MP 358-125 bullets as Dillon told me the same thing. The stock one is .351, mine's .3575 ish. I need my bullets to be .358 for my PT-92's rather large barrel. Case spring-back is .001. I assumed the .38 expander was going to be short. Have tried 15:1 and 50 / 50 alloys and both work well, the 50 / 50 I like a little better and it's cheeper as I only add about 1/2% Sn to it.
The results: