Quote Originally Posted by Mike_Mills View Post
ETA - if the primers are taller, you may need to run a small rifle primer pocket uniforming tool in the case to reform the primer pocket to the correct depth.
I know that I use rifle primers in my 500 S&W (Magnum/Match, in fact), those cases are designed for large rifle primers -- being designated w/ and 'R' on the headstamp.

But I did not know that 38 Super standardized on rifle primers. (Does it? I've read both opinions on line.) I'm gonna go measure both SP/SR primers tonight.

That said Mike M's advice to uniform the primer pockets is sound if you are going to use SR's though, and work the loads up for similar velocities as opposed to just substituting primers. Note also that rifle primer cup thickness is different/thicker, so check for hammer strike reliability as well.