Magnum primers for regular loads???

P

Prof Young

New member
Loaders:
What happens if I use small pistol magnum primers for standard loads? I'm specifically thinking of 9mm and 380. I ask because I wasn't paying attention at the gun store and bought magnums instead of regular.
Live well, be safe
Prof Young
 
You will have to reduce the load. If you are using a load in the upper 50% of the powder charge. Don't shoot them. Rather pull the bullets and redo the process.

As an alternative load a few batches from starting load in small increments and chronograph them. There where you exceed the maximum velocity listed by the powder manufacturer, you know this would be the maximum load. If your initial load is above the powder charge, you know for certain that you must pull those bullets.
 
I would not feel comfortable to tell anyone to use them for any loads that do not call for SPM primers. Especially in the small case of the 380. It is a blow back gun and my feeling is it would work the slide too much and has the possibility of cracking the frame.

My feeling is, it is more dependent upon the powder you are using than the cartage. A number or years ago I used SPM primers for all my 38 Spl. loads as well as for 357 Mag. I had no concerns because of the amount of space left open in the 38 case and wanted to insure powder ignition no matter where the powder was sitting in the case. Was it needed?, No. But it made me feel more confident that each round would go bang.

Can you use them for 9 MM, yes, but I would start at the Min load information and work up from there.

If you load a lot of 38 Spl, I would save them for those. Again, I am not tell you not to use them, but to be careful and work your way up.

Jim
 
A few questions for you before answering your question:
Which powder would you be using in your loads? What is the brand of the SPM primers you purchased?
 
Magnum primers burn a bit hotter for a bit longer. They're about the powder used.
Pressures might change a bit, but nothing horrible will happen. You should work up the load again just the same though. Or take 'em back or use 'em for something else.
Hodgdon, for unknown reasons, gives magnum primers in thusly named cartridges with the same powders.
 
In 9mm I worked up until the brass case failed.
I switched to a small magnum pistol primer and worked up again.
The brass case fails with 0.7 gr less powder and slightly less velocity at the threshold with the magnum primer.

I have some handguns that have weak hammer or firing pin springs and will not set off a magnum primer.

But if the primer is the weak spot, the magnum primer can take more powder in a work up before it pierces. There is significantly more velocity at the threshold with the magnum primer.

The worst of all worlds is a cheap old 25acp with terrible firing pin fit that pierces primers with wimpy loads, but cannot set off a magnum primer.
 
I have done this before. I backed off 10% and reworked and really didn't notice a difference. My loads were in larger capacity cases than 9mm and 380 though. YMMV
 
Hey, thanks for the info and . . .

Thanks for all the info. All makes sense to me. I think I'll see if the store will take them back and if not I'll just take them to the next gun show and see if I can trade them for something I can use.

Live well, be safe
Prof Young
 
Just work up from a starting load just like you would if you changed any other component.

Sometimes they make no difference. Other times you'll have more deviation in velocity. Sometimes they affect accurray. Sometimes they dont.
 
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