From Lyman's reloading Handbook "one set of tests have been conducted, where except for the primer identical components where used, wherein uniformity (the extreme spread of velocity and pressure) ran from as little as 38fps with one primer to 133fps with another. (!) This for a string of ten test shots. Pressure comparsions among the same group of test loads showed extreme spreads of pressure at as little as 3,500 psi to as much as 19,300 psi! The range of performance ran from very good to abysmal with the test load based solely on the primer used."
Unfortunately they do not give the primer manufacturers names. F-class shooters would be really interested in this due to the vertical stringing caused by as little as a 15fps deviation. Of note is that the majority bench rest competitors are using Federal primers. Anyone aware of any documented case studies of primer performance? ... of course experimenting to find out is part of the fun part, but the possibly of an extra 19,300 psi might be too much fun!

My notes contain similar data, this one from M.L. McPherson in an article over on sixgunner.com (a site sadly but a shadow of its former self):

Quote:

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Equally, note that primer
substitutions have been proven to sometimes radically alter pressure -- this
is not unique, ballisticians tell horror stories of customers who
haphazardly substituted primers and ran into king-sized problems -- for
example, combining a milder than suggested primer with Accurate #2 in a 9mm
load and doubling pressure! Moreover, neither you nor anyone else can
reliably predict results of any primer substitution! Use of a "hotter"
primer can result in lower pressure and use of a "milder" primer can result
in higher pressure -- any result is possible and all have been observed. It
is a unadulterated and unequivocal fact that anyone who professes to believe
they can predict even the general trend resulting from such a substitution
will have already demonstrated sufficient ignorance of reality as to make
the results of any handloading decision based upon their further
proclamations fraught with peril. Often such predictions hold, just as often
those do not.

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McPherson has published some tests he done to determine primer effectiveness. Some have shown up in recent issues of the Single Shot Rifle Journal.

Karl

I can't answer the question, but I can make a couple of comments that might be helpful.

1. Variation is a slippery devil. It is hard to estimate variation based on samples as small as 10. If you're chronographing 10 shots, and if the true standard deviation of the muzzle velocity is 35 fps, you will routinely get standard deviations as small as 26 and as large as 70, with no actual change in the process. If one 10 shot string gives you an SD of 30, and another 10 shot string gives you an SD of 60, there is no reason to believe that one is actually an different from the other. Same logic applies to pressure.

2. With H4350 and 4831, I find no difference in rifle pressure with CCI200 (regular large rifle) and CCI250 (magnum) primers, when I properly control both barrel and ammunition temperature.

3. Many of the "studies" done are highly suspect. Practically nobody truly controls chamber temperature, which is about 2-3X as strong a variable as powder temperature, which most people do control. What that means is that someone shoots 10 rounds of primer A, and records the MV or the pressure. Then they shoot 10 rounds of primer B, and, holy smokes, the pressure is much higher! Must be the primer, right? Not so fast! The barrel is now much hotter, and that might fully explain the change. In my instrumented Finnish M39 (308 to 30-06 class cartridge), one of my favorite loads gives around 52,000 PSI at 55 F, and about 59,000 PSI after I warm the barrel up to 95F. That happens after only a dozen rounds.

Check out this site.
http://www.castingstuff.com/
There is a very interesting comparison of most major primers.