substitute small rifle primers for small pistol magnums in 357?

irapollock

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Hi guys,
I'm wondering if any of you have used small rifle primers in place of small pistol magnum primers, especially in 357? The loads in question would be using H110 and Blue Dot.
Anything I should be aware of? I'll be starting over with load development at 10% under previous WSPM based loads. As you might guess present primer shortages are the reason for my question.
Thanks
 
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We've been doing this for decades.

If you start over, you're absolutely good to go, the only potential pitfall is if you have a light mainspring, the small rifle primer is a little harder to detonate. If you have a problem you are likely to discover it in double action fire, single action will almost surely pop it.

This last part, I'm not trying to sound mean — but you would not believe how many times this question has been asked in the last 1.5 years. This subject appears almost as often as new covid cases. ;)
 
You don't have to start over and work back up. SPMPs and SR primers are virtually the same except for a small difference in cup hardness. I like to do comparisons in my chronographing. Here's one I did that illustrates that.

Gun was my S&W mod 28-2 with a 4" barrel
Load-7.8 gr Hodgdon Longshot with a 158 gr cast SWC
SPMP vel- 1200 FPS ES- 53 FPS SR vel- 1198 FPS ES- 36 FPS
Velocity was essentially the same and consistency was a bit better with the SR primer in this test.
Forgot to add that primers used were Winchester.
 
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Not just Magnum handgun calibers. SR primers can substitute for SP primers in any cartridge - given that there is enough firing pin impact energy for reliable primer ignition. Check for that first. Ballistic performance differences will be minimal.

This is probably one of the most frequently asked questions here.
 
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