Primer's Impact upon Pressure

Barr · January 11, 2006, 11:31 AM

First, I know that you are not supposed to mix and match primers with recipes given in reloading manuals. I wonder how much primers affect pressure in the cartridge.

Secondly, I know that pressure is a function of volume. To make things simple let's consider the 9mm Parabellum Cartridge. It has a limited case capacity so primers should have a much greater effect on pressure than a large bore cartridge. The primers that I am interested in loading with are the Federal F100, CCI 500, and the Winchester WSP. My understanding is that the Winchesters are the "hottest".

My question is....Does anybody have any concrete numbers on these primers and how much they effect cartridge pressures?

Leftoverdj · January 11, 2006, 01:02 PM

Primers don't have enough effect on pressures to worry about in the normal metallic cartridge loading range. Switching primers might matter on very hot or very soft loads, but not in the midrange.

There are a handful of powders, mostly rifle powders, that need magnum primers. Primer changes can affect accuracy, but people make way too much fuss about them.

Use any of the primers you mentioned in the 9mm and it will work fine.

caz223 · January 12, 2006, 07:45 AM

Standard primers in the 9mm caliber are pretty much interchangeable.
I prefer standard primers as opposed to "for standard or magnum loads".
The bullet has WAAAAAAAAYYYY more to do with accuracy than primers, at least in 9mm and most other "standard" calibers.
10mm isn't what I'd consider a "standard" caliber, BTW.

WESHOOT2 · January 13, 2006, 06:37 AM

"...in MY gun..."

That's the correct question: how do different primers affect things in MY gun?

Actual pressure testing has shown us up to 5,000PSI differences.
Testing reveals certain combinations can visibly affect accuracy.

I test.

all guns are always different; my chamber or yours? my throat or yours? my breechface or yours? etc.

January 11, 2006, 11:31 AM	#1
Barr Senior Member Join Date: January 5, 2006 Location: Upstate SC Posts: 286	Primer's Impact upon Pressure First, I know that you are not supposed to mix and match primers with recipes given in reloading manuals. I wonder how much primers affect pressure in the cartridge. Secondly, I know that pressure is a function of volume. To make things simple let's consider the 9mm Parabellum Cartridge. It has a limited case capacity so primers should have a much greater effect on pressure than a large bore cartridge. The primers that I am interested in loading with are the Federal F100, CCI 500, and the Winchester WSP. My understanding is that the Winchesters are the "hottest". My question is....Does anybody have any concrete numbers on these primers and how much they effect cartridge pressures?

January 12, 2006, 07:45 AM	#3
caz223 Senior Member Join Date: May 15, 2002 Location: Michigan Posts: 1,429	Standard primers in the 9mm caliber are pretty much interchangeable. I prefer standard primers as opposed to "for standard or magnum loads". The bullet has WAAAAAAAAYYYY more to do with accuracy than primers, at least in 9mm and most other "standard" calibers. 10mm isn't what I'd consider a "standard" caliber, BTW. __________________ I'm not just a gun. I'm YOUR gun. (Hold me.)

January 13, 2006, 06:37 AM	#4
WESHOOT2 Senior Member Join Date: February 20, 1999 Location: home on the range; Vermont (Caspian country) Posts: 14,324	science "...in MY gun..." That's the correct question: how do different primers affect things in MY gun? Actual pressure testing has shown us up to 5,000PSI differences. Testing reveals certain combinations can visibly affect accuracy. I test. all guns are always different; my chamber or yours? my throat or yours? my breechface or yours? etc. __________________ . "all my ammo is mostly retired factory ammo"

January 11, 2006, 01:02 PM	#2
Leftoverdj Senior Member Join Date: October 15, 2004 Posts: 934	Primers don't have enough effect on pressures to worry about in the normal metallic cartridge loading range. Switching primers might matter on very hot or very soft loads, but not in the midrange. There are a handful of powders, mostly rifle powders, that need magnum primers. Primer changes can affect accuracy, but people make way too much fuss about them. Use any of the primers you mentioned in the 9mm and it will work fine.