Small Pistol VS Magnum Primers?

[x-Hare]

Ran out of my Small Pistol Magnum primers whats the difference between the SP & SPM primers.
I'm using Bullseye under a 158 SWC in a 357

 

[glenliz87]

The magnum primers are a bit hotter recommended for the slower burning powders. I've used both types with different powders. When using an x amount of powder with a regular primer, I had to back off about 1 grain if I wanted to use a magnum. I found there to be a slight velocity difference but not much. You don't need a mag primer with bullseye. I use Bullseye, Titegroup, Universal, 700X, Unique, 2400, SR4756 & SR4759 in my .357 with small pistol primers without any problems at all.

 

[x-Hare]

Thanks for that I'm not loading near the max and I thought with the Bullseye
I'm good to go/