Thread: Small rifle primers in pistol loads

Originally Posted by Marty Henry

The only difference as I understand it is the sr cups are made of slightly harder alloy designed to take higher pressure without the risk of rupture. Never use sp in rifles but sr fine in pistol cases was what I was taught.

A bit OT from the original posting but I swapped to SP primers in both my 22 Hornet (rifle) loads about a year ago. Groups noticeably shrank. Speer #14 manual even recommends SP for 22 Hornet. But you are right SR cups are harder, SP softer for the less powerful firing pin springs mechanisms in pistols compared to rifle. And there is a risk of a face full of gas using SP instead of SR say in for example 223 which runs at much higher pressure than the wee Hornet. Not sure what the 17 Hornets run at?

Edit: Might be wrong - the difference between SR and SP may be the thickness of the cup rather than difference in hardness.