A well lubed case thru the regular sizing die would do it, but not recommended... If you form the .357 case out of a .40 S&W, it will be .015-.020 too short...
Forming and trimming a 10mm cases isn't recommended either... It has a different internal configuration and also uses large pistol primers.
Best to buy once fired brass.
how much is it to reload 357 sig per 50 rounds? i plan on reloading for 40 and 9mm so really theres no reason to not reload some 357 sig.
I personally use 115 Montana Gold JHP in both my 9mm and 357sig loads
Have been using the Rainers 124gr in 4" barrel 357sig. Do the 115gr shoot better? Have you also tried 125gr?
Also what type of powder. Thanks.