I have 1000s (honestly) of 38 and 357s reloads at home. (each of my competition guns have a minimum of (5) 100 round boxes of competition ammo. plus plinkers. plus vacuum packed stashed ammo.) NONE have magnum pistol primers. I have loads with 4227, 296, 2400, Unique, Blue Dot, Red Dot, AA#9, Universal Clays, etc etc etc. Some of my competition rounds do use a small rifle primer vs a pistol primer, but that is because of the load I am using calls for the rifle primer. These are competition guns and are made to specs well exceeding SAAMI. Most standard 357s do not need the harder primer cup of the rifle primer and 99% don't need a magnum pistol primer.
I have used magnum primers in large volume rifle cases. Never in a pistol case.
A buddy of mine just went from WLP primer in his 41 mag to a CCI Mag pistol primer because WLP primers were not available. Worked back up to his load. NO DIFFERENCE in velocity or SD.
Read your reloading manual
s. I have many, PLUS there is lots of info on the internet. Work up your loads based upon knowledge. DO NOT GUESS. DO NOT ASSUME. Don't take just one manual as gospel. Read several.
If you look around Graybeards site you will find links to reloading manuals for about every brand of powder out there.
Just changing a primer in a pistol recipe can take a mild load to a WILD load! WILD loads hurt people and damage guns.
Learn learn learn, be safe safe safe, and then you can have FUN FUN FUN FUN FUN FUN FUN .
Steve