Primer Cup Diameter differences

preventec47 · January 6, 2010, 05:22 AM

http://www.jamescalhoon.com/primers_and_pressure.php

the above info could be very useful to anyone experiencing
loose primers I think.

It is hard to believe that different manufacturers
make large rifle primers of different sizes in diameter.

I would think that the larger diameter primers would
be harder to seat but I have never loaded these
primers side by side to compare

draggon · January 6, 2010, 06:15 AM

I looked at that data a long time ago (it was first published in 1995 according to the link) for that very reason and found that it wasn't as simple as that. Mere dimensions don't tell the whole story, materials and surface finish seem to make at least as much difference and at the end of the day the only way to be sure is to try a few different brands for fit.

Furthermore companies not only vary from batch to batch they make deliberate changes to accomadate new trends like progressive loading machines.

brickeyee · January 6, 2010, 01:01 PM

Any dimension has an allowable tolerance.

Most of the variation is out in the 4th decimal place, or ten thousandths of an inch.

I wonder how many hundred primers were measured to even get the values in the table?

The assumption about cup thickness being the only metric is also likely incorrect.

Brass work hardens very nicely, and different primers are well known to have varying hardness.

Pretty good in a mass production environment.

January 6, 2010, 05:22 AM	#1
preventec47 Junior member Join Date: October 13, 2008 Posts: 104	Primer Cup Diameter differences http://www.jamescalhoon.com/primers_and_pressure.php the above info could be very useful to anyone experiencing loose primers I think. It is hard to believe that different manufacturers make large rifle primers of different sizes in diameter. I would think that the larger diameter primers would be harder to seat but I have never loaded these primers side by side to compare

January 6, 2010, 06:15 AM	#2
draggon Member Join Date: April 16, 2009 Posts: 96	I looked at that data a long time ago (it was first published in 1995 according to the link) for that very reason and found that it wasn't as simple as that. Mere dimensions don't tell the whole story, materials and surface finish seem to make at least as much difference and at the end of the day the only way to be sure is to try a few different brands for fit. Furthermore companies not only vary from batch to batch they make deliberate changes to accomadate new trends like progressive loading machines.

January 6, 2010, 01:01 PM	#3
brickeyee Senior Member Join Date: December 29, 2004 Posts: 3,351	Any dimension has an allowable tolerance. Most of the variation is out in the 4th decimal place, or ten thousandths of an inch. I wonder how many hundred primers were measured to even get the values in the table? The assumption about cup thickness being the only metric is also likely incorrect. Brass work hardens very nicely, and different primers are well known to have varying hardness. Pretty good in a mass production environment.