primers and ignition affect sd and es
- Thread starter rockwind1
- Start date
Test other primers.
dcali
Bullet Maker
This is the totality of the answer.
dcali
Bullet Maker
Ok I take it back. There’s slightly more to it. The most vague, general advice is to use a mildest primer you can get away with. That means start with regular rather than magnum. Small rather than large. I’m sure manufacturers differ, but I’ve never seen a credible test that shows how they vary. Even the tests done by German Salazar a while back that are often cited are unacceptably vague. Much of the primer’s energy release is not visible. And it gets more complex from there. You really do just have to try them and see if it matters.
I recently had a load I developed shooting a ladder with a labradar next to it. The es was pretty steep but the group was there over a three shots. Switched to CCI 250s and es came way down. Velocity was the same. Some very dense powders like RL 26 seem to do better with hotter primers like fed 215 or CCI 250s.
Here is one article..... http://www.btgresearch.org/High-speed measurement of rifle primer blast waves.pdf
and another ... http://www.6mmbr.com/primerpix.html
and another ... http://www.6mmbr.com/primerpix.html
dcali
Bullet Maker
Thanks! I had not seen that. I'll take a look. The second one, however, is no good. You can't photograph the energy of a primer. It's not completely visible.
Edit: The first is suspect as well, unfortunately.
I do not think that German was looking at energy, more of the flame travel and brightness which could tell you how much energy is being spent
dcali
Bullet Maker
He was using the best he had available. Unfortunately, that's not a very useful measure for a variety of reasons. We don't really know how much energy is in the visible spectrum, and we do know that the combustion environment in open air is different than firing into a closed case full of powder.
The Michael Courtney paper is a little better in that it attempts to measure energy output, but he does it in such a half-assed way that he's basically shown that magnum > regular and large > small, and I'm not even willing to make that conclusion based on his work. Not exactly useful information. He's got a way of doing mundane things and making them look sciency in my opinion.
The Michael Courtney paper is a little better in that it attempts to measure energy output, but he does it in such a half-assed way that he's basically shown that magnum > regular and large > small, and I'm not even willing to make that conclusion based on his work. Not exactly useful information. He's got a way of doing mundane things and making them look sciency in my opinion.
A quote from the first study: "Standard deviation is a statistically valid measure of the variability of a quantity.(Extreme spread is a popular metric of a quantity ’s variability, but lacks statistical validity.)"
Now that should set the hair on fire of many posters
BoydAllen
Gold $$ Contributor
With all due respect to the author, I think his statement about the statistical validity of ES is wrong. Targets only care about ES. There is no SD trophy. So many refer to SD, so few could tell you how to calculate it, or have ever done that. They also tend to ignore the issue of sample size....completely.A quote from the first study: "Standard deviation is a statistically valid measure of the variability of a quantity.(Extreme spread is a popular metric of a quantity ’s variability, but lacks statistical validity.)"
Now that should set the hair on fire of many posters
I disagree. The target does see extreme spread but you cannot get a valid value of extreme spread form 10, 100, 1000 size-sample since it keeps growing with sample size (and you certainly can't get a decent value from the common 5-shot group). The best you can do is to get an idea of extreme spread from some multiple of SD. This is why much of industry uses 6 sigma for quality control.
BoydAllen
Gold $$ Contributor
Evidently you misunderstood me. I was referring to what shooters can do with the sample sizes they are afforded by their situations, not what is appropriate for manufacturers. They are two completely different situations, one involving very small samples and the other with the potential for very large. When I refer to ES I am referring to the actual extreme spread that a shooter gets shooting at a target, not some statistically generated number based on a sample size that reloaders would never use. My whole point is that what works well for one, is essentially useless for the other, where small samples are the rule. Take your method to a short range benchrest match, and see where it gets you. Loads are changed frequently, based on the results from one target, or even a few shots on a sighter target, by shooters who, at those distances are the best in the world. Similarly, tests that are performed by long range shooters must involve relatively small samples and because of the decreasing size of winning groups, more and more shooters are switching from preloading to at least giving themselves the option of adjusting loads at the range. This is absolutely not about manufacturing large amounts of a generic load.
One problem with measuring pressure effect of primers is that this test is only measuring one of two components of the energy of the primers, the other is heat content (first law of thermodynamics). A better test would be a test similar done for powders...a closed container where you can measure pressure AND temperature.
dcali
Bullet Maker
There's actually a method I've been toying around with that would be doable fairly inexpensively (but still a few thousand bucks) that only requires a pressure transducer and a metal fixture. It's like a closed bomb, but there's a vent in one end to let the gas escape. Between the pressure measurement and some fancy math, you can get a pretty good idea of things. And because it happens so fast, there's much less issue with heat transfer to the fixture. You basically calculate the mass flow rate leaving the bomb. Some guys did it back in the 70's and wrote up a paper on it.
The cost is the main problem. I'm sure it would be a fun project, but I'm not sure it's $3-4k worth of fun. But I bet you'd wind up with the best measure of commercial primers available outside of the industry.
The cost is the main problem. I'm sure it would be a fun project, but I'm not sure it's $3-4k worth of fun. But I bet you'd wind up with the best measure of commercial primers available outside of the industry.
You should add a temp sensor also. Problem is that you need a very fast response pressure and temp sensors or maybe cheaper sensors that capture the max values.
I don't remember the sample size if mentioned at all.
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