Can I substitute "small rifle" primers in loading data for the .357 Magnum? If yes, what adjustments, if any, would I need to make in that data? I've just come into about 2500 such primers and was hoping to use them in my SP101 loadings. Thanks!

they will fit fine, but may not go off. rifle primers are much less sensitive than are pistol primers.

I suspect that you won't be able to tell the difference in SR's and SP's. The SR should act about like a "magnum" SP and you should be able to use data accordingly. The nature of a hammer gun is that they deliver a pretty go blow to the primer. I doubt you'll have ignition problems. Load a few and see.

Unlike large rifle primers which have a taller cup than pistol primers, SR's and SP's have the same cup depth, so there is no problem with them failing to match the depth of the primer pocket.

I was under the impression that small rifle primers are taller than pistol primers as well as having thicker cups. If I was going to try using SR primers to replace SP primers i would drop the charge by 10% and work it back up watching for signs of over-pressure as I did. There is a lot of difference in pop between the two. It may affect some powders more than others and it may be less difference if you are using magnum SP primers but there is only one way to be safe when you change any component.
"With any change in components you should, for safety sake, reduce your charge an appropriate amount and work the load up while watching for signs of excessive pressure"

quote:

Originally posted by PaulS:
I was under the impression that small rifle primers are taller than pistol primers as well as having thicker cups.

Unlike large rifle primers which have a taller cup than pistol primers, SR's and SP's have the same cup depth, so there is no problem with them failing to match the depth of the primer pocket.

As many Hornet and other small caliber rifle shooters know, small pistol primers are of the same dimensions as small rifle primers. SP primers are frequently used in rifle calibers because they often give superior results in small cases like the .22 Hornet.