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Discussion Starter #1
I’ve been loading for a few decades now and always try to keep close to the recipes from the manufacturers. However, it seems that all the data calls lately for magnum primers in 357 cases regardless of the poEder. I’m planning to load some 158 gr rnfp bullets on top of a light load of 231 for cowboy action. Ive got several thousand standard small pistol primers but fewer than 500 magnum. Am I flirting with disaster or irregular firing results by going with standard, non-magnum, primers?
 

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No, you should be fine. Magnum primers are needed for slow burning, hard to completely ignite powders that fill the case (16-20 grains), like Winchester 296. I use standard primers in my 130gr magnum loads with 7.7gr of Unique, but magnum primers in 158gr loads with H110, win 296 & Blue dot
 

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The reloading manuals are not "recipe books" for making ammunition. They are documentation of controlled and measured experiments.

When you substitute components, you are in effect performing your own experiments. If you don't have measurement instrumentation, you're doing it blind. That's experimenting with 35,000 to 50,000 PSI pressures in the blind, in your hand.

The mix of components interact in very unpredictable ways. Magnum primers are hotter and tend to ignite powder in a different pattern than standard primers. When powder burns, it can generate multiple peak pressure points over time.

The case volume of a .357 case is also larger than a .38 special. This will change the timing and peak pressure between the instant of ignition, pushing the bullet out of the case, jumping the gap to the leade into the rifling, engaging and cutting the bullet lead or jacket into the rifling and the delay before it starts moving and increasing the volume.

Note that under powered loads (which end up delaying the engagement into the leade) can cause dangerous over pressure. This is not relieved by the cylinder gap because a bullet can block that while engaging into the leade. It's generally not until after moving down the barrel that the bullet clears the gap allowing pressure to be relieved.

I personally don't do such substitutions; don't recommend doing them and teach that you should follow reloading guides precisely.
 

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Discussion Starter #4
The reloading manuals are not "recipe books" for making ammunition. They are documentation of controlled and measured experiments.

When you substitute components, you are in effect performing your own experiments. If you don't have measurement instrumentation, you're doing it blind. That's experimenting with 35,000 to 50,000 PSI pressures in the blind, in your hand.

The mix of components interact in very unpredictable ways. Magnum primers are hotter and tend to ignite powder in a different pattern than standard primers. When powder burns, it can generate multiple peak pressure points over time.

The case volume of a .357 case is also larger than a .38 special. This will change the timing and peak pressure between the instant of ignition, pushing the bullet out of the case, jumping the gap to the leade into the rifling, engaging and cutting the bullet lead or jacket into the rifling and the delay before it starts moving and increasing the volume.

I personally don't do such substitutions; don't recommend doing them and teach that you should follow reloading guides precisely.
Thank you.
 

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Discussion Starter #5
No, you should be fine. Magnum primers are needed for slow burning, hard to completely ignite powders that fill the case (16-20 grains), like Winchester 296. I use standard primers in my 130gr magnum loads with 7.7gr of Unique, but magnum primers in 158gr loads with H110, win 296 & Blue dot
Thanks
 

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For target loads that are under max, I sure wouldn't let the fact that I don't have magnum primers laying around stop me from working up a load. I think I'd hang on until I had them, though, for full power loads.
 

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I have always used what my manual told me to use. If it said use a magnum primer with this load I bought some magnum primers. I NEVER substituted anything.
 

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Discussion Starter #8
I appreciate the responses and will accede to your collective wisdom.
d
 

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I suppose it depends on your load..I load Magnums with 2400 or AA#9. 357,44 & 500 fly well with standard primers.

thewelshm
 
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Thank you.
The reloading manuals are not "recipe books" for making ammunition. They are documentation of controlled and measured experiments.

When you substitute components, you are in effect performing your own experiments. If you don't have measurement instrumentation, you're doing it blind. That's experimenting with 35,000 to 50,000 PSI pressures in the blind, in your hand.

The mix of components interact in very unpredictable ways. Magnum primers are hotter and tend to ignite powder in a different pattern than standard primers. When powder burns, it can generate multiple peak pressure points over time.

The case volume of a .357 case is also larger than a .38 special. This will change the timing and peak pressure between the instant of ignition, pushing the bullet out of the case, jumping the gap to the leade into the rifling, engaging and cutting the bullet lead or jacket into the rifling and the delay before it starts moving and increasing the volume.

Note that under powered loads (which end up delaying the engagement into the leade) can cause dangerous over pressure. This is not relieved by the cylinder gap because a bullet can block that while engaging into the leade. It's generally not until after moving down the barrel that the bullet clears the gap allowing pressure to be relieved.

I personally don't do such substitutions; don't recommend doing them and teach that you should follow reloading guides precisely.
I can find load data that says to use standard primers with his chosen powder. so he would not be in uncharted territory
 

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VihtaVuori specifies small rifle primers for their .357mag data, Sierra specifies small rifle primers for .38 Super and there is published data using small pistol primers with .357mag and 2400.

The OP should be okay with using regular primers for this particular loading. :)
 

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Save the magnum primers for magnum loads. You'll be fine with a standard primer and a light load of 231. I've shot a bunch of them. Somebody probably read that 231 is a Ball powder and also read somewhere that Ball powders require a magnum primer. What you might see is a little bit less velocity. FWIW, I don't use a magnum primer with my 2400 loads but do with H110 or WW296.
 

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I have used magnum primers exclusively for all of my handgun loads for a long time. i use federal for all my revolvers since most have trigger jobs with light actions and won’t shoot hard primers like CCI. Federal got impossible to find except magnums so I carefully worked up some light loads and there is no noticeable difference with fast burning powder like Bullseye or mid burning like Unique. Velocity is basically the same and I found that mid range powder seems to burn cleaner. I’ve also noticed that Winchester primers now state standard/magnum on the box. I was especially cautious with 9mm since smaller cases seem to have pressure increases with minor changes more than 38 or 44 cases. Again, no issues but I’ve always loaded 9mm pretty light.
 
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