Omni -

My reference was only to small rifle primers. Big bore (large rifle primers) isn't an issue because all the cups are the same thickness.

44Marty -

I'm going to have to back up a bit and reconsider what you said about Rem 7 1/2 primers being magnum.

I just came across this test showing the primer flash from different SR primers. Based on the flash and pressure, I'd say it was magnum level.

riflemansjournal.blogs...study.html

My apologies.

I found this article about primers and a study of brislance pressure and velocity. it is a good read.
www.btgresearch.org/Hi...0waves.pdf

HayCreek wrote:

I just came across this test showing the primer flash from different SR primers.

The picture of the 205M is the old version........ Today's version 205M is a lot hotter !!!

inthedark wrote:

it is a good read.

Great !!! Now I need one of them there $$$ scales !!! Does it ever end ???

HayCreek wrote:

44Marty - I'm going to have to back up a bit and reconsider what you said about Rem 7 1/2 primers being magnum. I just came across this test showing the primer flash from different SR primers. Based on the flash and pressure, I'd say it was magnum level. riflemansjournal.blogs...study.html My apologies.

Very interesting article and follow-up article. A point briefly mentioned is something I have found to hold pretty true as a generality. The most accurate loads are those in which the powder most completely fills the case.

I was way off base about primers, according to the studies in the article. I had always thought that a hotter primer generally gave more consistent powder ignition. The quote below I have highlighted in bold seems to explain their view most simply.

Interesting exerpts from the articles:

Details of Bob’s pioneering tests can be found in: Highpower Rifle Shooting Volume III, NRA, 1983, Handloading Techniques and Long Range Shooting Techniques, Bob Jensen, p. 60. A very brief summary of Bob’s findings in that early series of tests, is that those primers which produced the lowest average velocity in his specially built Winchester Model 70 test rig (which fired BBs powered only by primers) produced the best accuracy in actual ammunition.
and:
We begin our process of data interpretation by bearing in mind Bob’s early tests with the primer-powered, BB firing Model 70. Those test showed that the primers which produced the lowest velocities with reasonable SD in the Model 70 “BB gun” were the most accurate at 600 to 1000 yards when loaded in .308 ammunition. In fact, our own testing with the 6BR showed that the most accurate primers at 600 yards were those which produced the lowest velocities. Remember, you can always adjust velocities with the powder charge, if needed for accuracy reasons; the issue isn’t low velocity per se, but rather the primer’s contribution to the velocity. The reason for this is that the primer contributes energy to the system in a manner quite disproportionate to its size; however, the precision with which priming compound is measured and dispensed into the cups is somewhat less than the precision with which a careful handloader measures and weighs powder charges. Accordingly, a high energy primer with (for example) 5% energy variability, will have a greater absolute effect on total energy variability than will a lower energy primer having the same 5% variability. A milder, softer primer is a more consistent primer. All of this assumes that the primer in question has sufficient energy to reliably ignite the powder charge in the relevant environmental conditions and sufficient cup thickness and hardness to resist blanking under the pressure generated. The magnum primer has a useful purpose, for instance, but firing mid-size cases on the target range in the summer is not that purpose.

Also:
We began the first article with reference to the soft primer of the corrosive primer era and its presumed beneficial effect on accuracy. I believe that we have demonstrated that a softer primer is beneficial to accuracy. Generally speaking, a primer with three characteristics: a small visual flash, relatively lower pressure and relatively lower muzzle velocity than its peers, is our definition of a soft primer that will maximize accuracy. Some primers embody one or two of those three characteristics and they may be acceptable in many loads, but for our purposes, all three must be met for the accurate characterization of a primer as a “soft primer”.

EDIT: . . . . and from the second link:

2) For most primer types tested, peak pressure magnitudes are well correlated with measured primer masses so that significant reductions in standard deviation are expected to result from sorting primers by mass.

My head is starting to hurt - Now I should not only be sorting brass by internal volume and bullets by weight, but primers by weight also in order to get the most accuracy??

I think I'm going to go back to the "minute of deer" approach and give up on my search for the most accurate firearm. I don't think I'll ever get any better than I had it with my .204 anyway, unless I invest in a rail gun.

Quote::

My head is starting to hurt - Now I should not only be sorting brass by internal volume and bullets by weight, but primers by weight also in order to get the most accuracy??

Mine, too!

Problem is, I love trying to put 5 bullets into the smallest hole. I don't think I'll go as far as weighing the primers, tho'. What they say about the hotter primers having the greatest effect on velocity due to a mere 5% variability makes me consider finding a softer primer to test.

I've already tried CCI 400s but as I mentioned before, the cup is too thin for the .204 pressures. The Fed 205M looks about right in the pic, but Chambered221 says that's the older one and the new ones are hotter. What's a guy to do?

HayCreek, Just keep testing! Each firearm has its individual preference anyway. If nothing else you'll get to shoot more!

Yeah, guess I'll shoot out this barrel and test another one. Here's to more shootin' !!

Try the CCI BR4....... It has the .025 thickness, heat range is between the 400 and 450 !!!

Ok. Will do. Gotta go to town tomorrow, anyway. Might as well pick up a pack to test.

Then, the hard part...testing in cold weather. Temps are dropping, here, and I'm going to have to minimize another variable. Namely, a cold trigger finger!
The things we do in the name of science.

HayCreek wrote:

Ok. Will do. Gotta go to town tomorrow, anyway. Might as well pick up a pack to test. Then, the hard part...testing in cold weather. Temps are dropping, here, and I'm going to have to minimize another variable. Namely, a cold trigger finger! The things we do in the name of science.

Rem 7 1/2 and CCI 450 primers both worked perfectly after spending a few days in the freezer at -4* F
I never did try standard primers in my .204 just magnum and benchrest. It would put 3 rounds into a hole you couldn't tell apart from the hole from a single round at 125 yards with magnum primers, Sierra 39gr BlitzKing bullets, Nosler custom brass and 25.6gr IMR3031 powder regardless of temperature and weather. I shot in weather ranging from 85*F and sunny to -10*F and snowing. (That was a freaky day - it usually doesn't snow here when it's that cold out. Talk about a cold trigger finger!!)

Quote::

Rem 7 1/2 and CCI 450 primers both worked perfectly after spending a few days in the freezer at -4* F

Good to know, marty. Just picked up 200 BR4s to test. I sorta hope they do better than the Rems. But, then again, I sorta don't...they're more expensive!

You're one of the many shooters that get good performance with the SBKs. Me...that's another story. The dang things come out cockeyed in my rifle. Nosler and Hornady bullets - no problem.

Interesting about the 3031. Never tried it in the .204. Seems to be in the catagory of Hodgdon's extreme powders, although not so listed. Dang! another test coming, I think.

BTW- darn fine shooting!
Best I've gotten is .2" c-c but not consistently enough. That's why I'm looking at primers after reading those tests.

I may have discovered something here... the exact same load

Ruger 204

28.5 grains Varget 32gr V-MAX

@ sea level
CCI400 primers = evidence of cratering
Reminton 7 1/2 primer = no issues

@4000ft
CCI400 Primers = no issues, can even push load to 29.5 grains without issues

Remington 7 1/2's are listed as "BR" primers or Bench Rest primers

gelandangan wrote:

In my 300 Whisper, magnum primers gave consistently lower MV than standard primers. I am sure I have checked and double checked my primers, I have also purchased a fresh box from another supplier just to try. It must be because of the low charge amount.

Yeah but you were burning coal! lo,l