Question on Small Pistol MAGNUM Primers

[tsafa]

Hi all.

I am reloading .357. The book says to use "small pistol primers"...
What about "small pistol MAGNUM primers" ???

What would small pistol Magnum primers be used for if not for a .357?

Some testing I did with light loads reveals a 25% increase in Energy with a Magnum Primer instead of a regular Small Pistol Primer.

Thanks for any feedback on this.

[Brick]

Use Small Pistol Magnum primers in loads that reference them in your manuals. There are some .357 Mag loads that need them to get the powder lit off correctly. Again read your manuals!

Small pistol Magnum primers may be used in loads that don't normally require them. But when and if you do so it usually requires an adjustment to a lighter powder charge. SO go back to the starting charge weight and work up incrementally until you achieve the performance you desire, all the while watching for signs of excess pressure.

[knight0334]

With that 25% increase in energy there will be an equivalent increase in pressures.

When you load .357mag to the wussified levels of today, then use a magnum primer - you'll get good results within safe operating standards. But if you use true 357mag loads and use mag primers - you can push your load beyond spec levels for the cartridge and for the guns.

You should always back off upper end loads when using mag primers. The hotter ignition will increase flame propagation, which in turn will burn the powder faster, which in turn will increase pressures.

[tsafa]

Very interesting feedback. Given that it is harder to get powder these days, it seems like a good idea to go with lighter loads and use magnum primers. The price of the regular primers and the magnum primers is the same.

[Brick]

Very interesting feedback. Given that it is harder to get powder these days, it seems like a good idea to go with lighter loads and use magnum primers. The price of the regular primers and the magnum primers is the same.

You aren't going to save enough in powder to make a noticeable difference. One or two tenths of a grain for a moderate .38 Spec. load will take 54 (if 0.1) or 27 (if 0.2) reloaded cartridges to save enough powder to reload one additional cartridge. Or if you prefer think on it as needing that 0.1 grains 70,000 time to make up a pound of powder.

Your best bet, use magnum primers when the load data calls for them. Use magnum primers as a substitute for standard only in a pinch when standard primers have turned into unobtainium!

[noylj]

The magnum primers burn hotter. This is needed for certain magnum primers (see 296/H110 in your reloading manuals). Standard primers, when called out, are generally more accurate.
Hornady only specifies magnum primers for all powders in their manuals, but then, they don't use any powders other than magnum powders. No 231/HP38 or other fast powders.
As a reloader, you can try both and see what works for your gun.

[deafsmithco]

From Handloader 285 page 25 in his "From The Hip" Brian Pearce says " Don't do it".

Not word for word from the column, but you get the idea:

Changing to a magnum primer can jump pressure 5000-15000psi or more. Smaller cases such as .380, 9mm and .40S&W suffer from it the most. But even larger cases will be affected by it.

Some powders are worse then others with the pressure increase, also.

Brian, in my opinion, is one of the best and he has friends and contacts in the industry, as I am sure all writers do.

Bottom line for me at least since I don't have a pressure barrel, is to heed his words.

I would recommend that anyone who is going to switch primers to at least contact the manufacturer of both the primer and powder being used. They should be able to give you an idea as to what you are up against.

[bfoosh006]

Hi all.

I am reloading .357. The book says to use "small pistol primers"...
What about "small pistol MAGNUM primers" ???

What would small pistol Magnum primers be used for if not for a .357?

Some testing I did with light loads reveals a 25% increase in Energy with a Magnum Primer instead of a regular Small Pistol Primer.

Thanks for any feedback on this.

If you look at Remington Factory .40 ammo , it is loaded with Remingtons SP Magnum primers.