With our current primer “shortage”, there’s been some discussion recently about the use of Small Rifle primers in the place of Small Pistol. Honestly, I had tried it before, with satisfactory results, but I’d never chronographed the loads to see if the rifle primers make a difference. So, for a test I put together 50 rounds of .357 Mag for testing with my S&W 66 (4” bbl)
- PPU brass
- Lyman 358156 GC
- 10.8 gr of 2400 (thrown by a Pacific Pistol Powder Measure which uses bushings like a MEC)
- 10 rounds each with the following primers; Win SPM, FIO SR, Win SR, Rem 6 1/2 SR, CCI-400
I didn’t test for accuracy, just velocity, and they ended up grouping similar at 10yds but here’s the 10 round average velocity as recorded by my Chrony Beta:
Win SPM (Small Pistol Mag used as the control) – AVG 1140 fps
Fiocchi SR – AVG 1084 fps
Win SR – AVG 1186 fps
Rem 6 ˝ SR – AVG 1117 fps
CCI-400 – AVG 1155 fps
I've read that SPM and SR have the same brisance and I would tend to believe it as the velocity was similar for all primers. Also, none of the brass showed any signs of excessive pressure, and as harder primer cup was a concern, all fired normally - none required a second strike of the hammer (my pistol has the stock mainspring).
Yes, this is totally unscientific but it was interesting (at least to me). I’m perfectly comfortable repeating this test with other small pistol calibers (.38 special, 9mm, and .40 S&W) and would suspect similar results. Of course, starting at minimum loads and working up is always sound advice but it does seem that if the need arises, substituting SR for SP isn’t that much of a problem.
Semper Fi.