Small Rifle Primer - 357 Mag. Test

[Headhog]

Final got to the range today to do some chrono testing of small rifle primers in 357 Mag loads. Many of us reloaders had various stocks of different primers, powder and components before the panic buying of 2020. But as our stocks dwindled, getting certain components has been almost impossible. I've had a very plentiful supply of small pistol primers and small rifle primers but a limited supply of magnum small pistol primers. So after a prior thread (http://henryrifleforums.com/viewtopic.php?f=20&t=11371) using small rifle primers in place of magnum small pistol primers I decided to make up some test loads and here are my results and conclusions.

The load I'm testing is my goto 357 Mag. load for my Henry BBS or Rossi R92. I'm using various fired 357 Mag. brass with a 158 gr Missouri coated bullet and 6.2 gr. of Universal, loaded to 1.585". Normally I use a magnum primer like CCI 550. For the test, I substituted Winchester WSR (non-magnum) primers for the CCI 550. I made 20 rounds (10 for each) to chrono in both of my 357 Mag. rifles. The chrono showed average velocity of 1245 fps from the Henry and 1262 fps from the Rossi. This was identical to the results I tested, for this load, back in February.

Afterwards I examined the cases for any signs of excess pressure and again they appear the same as my control group for this load. No primer flattening, case bulges of anything else that would indicate a problem. Even the standard deviation and extreme spread of the load was well within the margin of error I would expect.

So going forward I would feel perfectly comfortable using small rifle primers (SRP) in any load calling for magnum small pistol primers (MSPP). I plan to stop buying MSPP and just keep SRP in my cabinet. The SRP seat to a the same depth and produce identical powder ignition and velocities. The only downside I can see is the possibility of misfires in some firearms. SRP have a slightly thicker cup to handle the additional pressure of typical rifle loads. So some pistol shooters and those folks that have performed trigger lightening work on their firearms may experience misfires.

Every reloader has to make their own choices of what is right and safe for them. I'm not not an expert just and active reloader and my only testing is via the chrono results and carefully observation. If you choose to go this route, please do so with caution. If you make this substitution, work your way up slowly watching for any pressure signs. Please remember, I tested only one reload recipe, so I have a very small sample of data. This, for me, is my goto 357 mag load so I'm comfortable with the results I obtained.

Paul

[runnin n gunnin]

Thanks Headhog, Outstanding info and test. I very much appreciate the info. I am printing your post and will duplicate your test rounds to see where I am at. My go to for .357 has been Unique or 2400.

I have been looking forward to your post, thanks for the work.

[Vaquero]

Yes sir good info, Thanks for the update.
Most all my 357 loads lately have been with 2400 and the MB Pugnose 180's.
But I only use standard SP.
I do have some magnum LR primers that I need to find a use for.
Was told they work well with 748 in the 30-30, but
I've yet to try.

RP

[runnin n gunnin]

Roger that Vaquero, love those 180 grain MB pugs.

[BigAl52]

I have read where lots of guys use SR primers only for pistol and rifle to simplify things and only keep one primer around.

[JEBar]

So going forward I would feel perfectly comfortable using small rifle primers (SRP) in any load calling for magnum small pistol primers (MSPP). I plan to stop buying MSPP and just keep SRP in my cabinet. The SRP seat to a the same depth and produce identical powder ignition and velocities. The only downside I can see is the possibility of misfires in some firearms. SRP have a slightly thicker cup to handle the additional pressure of typical rifle loads. So some pistol shooters and those folks that have performed trigger lightening work on their firearms may experience misfires.

Paul

thanks for your reporting .... while I haven't done anywhere near the level of research, what I have experienced has been pretty much the same .... so far, no problem with light strike misfires but I can see how that could happen