Primer Questions

[Old SF MJT]

I did a search, but couldn't find anything, so here goes!

What is the difference between a pistol primer & a rifle primer? What about between a standard primer & a 'magnum' primer? What will likely occur if they are crossed up - a pistol primer in a rifle round or a rifle primer in a pistol round?

I feel stupid asking this, but I can't seem to find any information on this & REALLY don't want to screw the pooch.

Also, what about loading such rounds as the .30 Carbine? Rifle or pistol primer?

Thanks in advance for the assist.
Old SF

 

[Deanimator]

Most if not all of the difference between rifle, pistol, standard and magnum primers is the "brisance" or energy of the priming compound.

Rifle primers have more brisance than pistol primers and magnums more so than standard primers.

Using a rifle primer when a pistol primer is called for, or a magnum primer when a standard primer is called for will increase pressures, possibly dangerously.

 

[Steve C]

Also, what about loading such rounds as the .30 Carbine? Rifle or pistol primer?

You should always use the primer type specified in the loading manual. Its even a good idea to use the same brand of primer if you expect to duplicate the results given in the manual.

Besides being “hotter” as Deanimator describes, rifle primers are usually “harder” in that they need a heavy firing pin strike to set them off reliably. Because the pressures in a rifle cartridge is generally much greater than what you see in a pistol cartridge the cup material is made thicker to withstand this higher pressure.

Large rifle primers are also taller than large pistol primers. If you use a large rifle primer is a cartridge designed for large pistol (ex. .45 acp) then you would see the base of the primer rising above the base of the cartridge. You can guess how I kow this.

 

[snuffy]

"Most if not all of the difference between rifle, pistol, standard and magnum primers is the "brisance" or energy of the priming compound."

Not entirely true. One of the main differences is the thickness of the actual cup, so that in the rifle primers, they can withstand the higher pressures generated. Ignition problems could result if the hammer fall/firing pin hit is a bit light in a handgun when using rifle primers. There's also a height difference between lg pistol and lg rifle primers. With the rifle primers being taller, you can't seat them deep enough in a pistol cartridge to be below flush. That could tie up a revolver cylinder.

 

[Plastic Cowboy]

An example of the difference between pistol and rifle primers:

For those of you not familiar with reloading for the big S&W 500 magnum revolver--
the original brass manufactured for this caliber used large magnum pistol primers (seems to make sense right?)

Well the 500 mag operates at pressures in excess of 50,000psi for full house loads and what Smith & Wesson discovered was that the large pistol primers were burning through and damaging the firing pin at these pressures. In response all manufacturers of 500 mag brass have enlarged the primer pockets to accept Large Rifle Primers which have enough increased strength to withstand this enormous heat and pressure.

(Large Rifle primed cases are marked with an "R" on the headstamp- your life depends on using the correct primer for this big boy since a rifle primer in a pistol pocket extends above the case head and can detonate in a non-firing chamber under the immense recoil and at nearly a ton and a half of muzzle energy per round this will ruin your day and anyone else unfortunate enough to be in the general area!!!)

 

[Grumulkin]

I have experimented with magnum and regular primers with a number of loads. For larger volume rifle cases, I have yet to find a significant pressure difference when interchangeing primers however, I work up these loads cautiously as there are bound to be exceptions.

In the case of a 44 Rem. Mag., the pressure did get higher sooner with the magnum primers.

There can also be accuracy differences with different primers. When loading for a 357 Herrett with IMR 4227, I found definite preference for CCI 250 large rifle magnum primers for instance. Most of the time, there isn't a big accuracy difference though. Also, some cartridges called "magnum" don't necessairly shoot the best with magnum primers. I only use regular large rifle primers when loading for my 7mm Rem. Mag.