The slow powders like W296, H-110, AA#9, Alliant 2400, and VV-110 will require magnum primers.
These powders are the "traditional" favorites for full-throttle magnum loads.
I like to use a stout charge of Alliant Blue Dot for the simple reason that this powder does not require magnum primers.
I have used W296 and H-110 and they are excellent too, but don't allow much in the way of reduced loads.
As always, consult published reloading data from a reputable source.
Hope this helps.
The ball powders like W296 and H110 need all the help they can get, or you'll have high extreme spreads in velocity. Old Elmer was right about 2400, it likes a soft start with standard primers and you can go faster with them. I've had things get spooky with magnum primers and 2400. Check out Speer's latest bullet (99K). http://www.speer-bullets.com/pdf/ReloadingSupplementalDATA/357mg170.pdf
Brian Pearce tested most available primers for the .357 in Handloader #207, Oct-Nov 2000.
I reload mild .357s for kids, and plinking loads, if I load for my GP-100 with 6" barrel and want power I use H-110, but for my SP-101, I use a 125 gr. JHP with W231 8. gr.s, thats under Speers
max data, alot less flash and no unburned powder, and no mag
primer.this is out of Speer manual 13, HS-6 uses a mag primer and has less velocity, these are low end loads compared to other
powders, used to use SO much Unique, but can't find it anymore
alot of W231 though.
Generally, the 357 Magnum requires magnum pistol primers, as does the 41 Magnum and the 44 Magnum. Magnum pistol primers were made for these calibers. I always use magnum pistol primers in these calibers; it won't hurt anything (all my handloads are chronographed) and it eliminates lots of confusion.