Standard vs. Magnum Primers

Modeler · Feb 20, 2013

In these times of primer shortages, I have to ask:

What's the difference between standard and magnum primers?

Is it ok to use magnum primers in standard loads like 9mm or .40?

Is it ok to use standard primers in magnum loads like .357?

ma96782 · Feb 21, 2013

A good reloading manual will spec a standard or magnum primer, depending on the cartridge, powder and/or bullet being used. For liability sake I can only say to use what the manual says to use. Now, that being said you control the process, never start with the hottest load mentioned in the books. Start low and work your way up. Watch for the signs of overpressure. If you are going to replace a magnum for standard primer, lower your powder charge a bit to compensate.

From the Speer Manual #10

Magnum Primers

Magnum primers contain a greater amount and/or slightly different explosive mix than is used in standard primers. On ignition, magnum primers give longer burning, hotter flames. Their use is recommended for (1) any ammunition that will be used at or below zero degrees F., (2) with most Ball powders and (3) with slow burning rifle powders like MRP and IMR 4831 in very large cases. Magnum pistol primers often will give more uniform velocities in magnum handgun cartridges loaded with large charges or slow powders like 296, 2400 and H-110. Magnum primers may be used with faster burning or easy-to-ignite powders, but normally there will be no advantage in doing so. As when changing other components, it is advisable to reduce powder charge weights on initial loading with magnum primers.

Run your tests and choose what YOU like.

And, the various manufacturers can and will change things up (chemical mixes, materials specs., etc.......) to suit their own criteria. So, don't assume that one brand can just replace another either.

Aloha, Mark

Trailboss · Feb 21, 2013

Yes to both, but you have to start low and work your loads up again. The different primer heat can affect pressure so start slow and find the perfect load.

nwdrifter · Feb 21, 2013

i have never noticed a difference and use mags a lot..

Modeler · Feb 21, 2013

Thanks for the info. I have used magnum primers in standard 9mm loads and they seemed to work fine, now I'm getting ready to load .357 magnum in the coming months and I was curious to know what the difference was.

Thanks!

SinisterSouthpaw · Feb 21, 2013

I ran out of small pistol magnum primers during the last Obama panic and had to use standard primers in my .357 loads. These loads are just for paper punching and are lighter than some folks may be using in the same caliber. Shooting 158 gr. JHP or plated FNs propelled by Lil' Gun powder in various doses, I noticed no difference on target. When mag primers became available again, I bought some, since I also carry a magnum caliber and I want that gun to light up the load strongly. Since I only use the standards for the target guns I have plenty of primers to get me through this current silliness.

rrojohnso · Feb 22, 2013

This leads to a great question regarding Rifle primers - same thing: Using a Mag primer in a lg rifle primer pocket. Has anyone had any experience in using a Mag primer with a mid to slow burning powder in a .308? I asked one loader, and he said you'd never notice a difference. As one to be skeptical, it seems a really hot primer (mag) and a slower burning powder could create a smoother pressure curve, which would potentially mean softer recoil, but also greater consistency down range? Thoughts?

deadshot2 · Feb 22, 2013

rrojohnso said:
As one to be skeptical, it seems a really hot primer (mag) and a slower burning powder could create a smoother pressure curve, which would potentially mean softer recoil, but also greater consistency down range? Thoughts?

Or a lot of burning powder ejected from the muzzle for a nice flash.

As I understand the whole process, the primer's job is to merely light off the powder column in the case. Some powders, notoriously ball powders, are hard to light. Most slow powders are stick and easier to light. I'm not sure that the primer is really part of the recoil equation though.

A load where the primer characteristics and the powder characteristics are matched to bullet and barrel will yield the best accuracy. Some do it with magnum primers and some with standard. All depends on how you adjust the rest of the variables.