Weight sorting primers-Test
- Thread starter Dave Way
- Start date
My wife has been out of town, so I decided today to weight sort my CCI 450 primers....about 5hr work! My hope is that if I sort in groups of 2, it might add to better consistency. It will be a good test to see if the group size changes with the only reloading change being the primer weight variance.....oh, plus the other 10+ reloading prep/processes. Next it will be about my wind reading skills and any variance caused by my bench skills.
The hunt never ends,
Ben
butchlambert
Site $$ Sponsor
Well, probably the only difference is price only.
Mark Buettgen's son works for Federal and Mark told me that there is NO difference in 205's and 205 M's. However, the M's get a visual inspection and the 205's do not.
Dusty Stevens
Shiner
Exactly right. Hes not the only primer rep that has told us that.
I like this:
https://arxiv.org/ftp/arxiv/papers/1102/1102.1644.pdf
some quotes:
"match primers are not always more consistent than non-match types"
'total mass and explosive mass tested peak pressure magnitudes are well correlated with measured primer masses"
CCI 450 or at least a certain lot of CCI 450's would not correlate for mass & pressure.
".....since most of the slopes of peak pressure vs. primer mass are between 8 and 20 psi/mg achieving variations in peak primer blast pressure below 10 psi will likely require sorting primers into groups on the order of 1/4 - 1/2 mg …. this requires a scale with a precision of .1 milligram"
This type of scale would be an analytic laboratory scale - not likely to be on some shooter's bench.
Interesting observation about the black stuff - most likely heavy metal residues from explosive primer compounds. I believe almost all of the back residue cleaned out of rifle barrels is not carbon.
Visual inspection of zillions of primers might cause some psychologic impairment.
https://arxiv.org/ftp/arxiv/papers/1102/1102.1644.pdf
some quotes:
"match primers are not always more consistent than non-match types"
'total mass and explosive mass tested peak pressure magnitudes are well correlated with measured primer masses"
CCI 450 or at least a certain lot of CCI 450's would not correlate for mass & pressure.
".....since most of the slopes of peak pressure vs. primer mass are between 8 and 20 psi/mg achieving variations in peak primer blast pressure below 10 psi will likely require sorting primers into groups on the order of 1/4 - 1/2 mg …. this requires a scale with a precision of .1 milligram"
This type of scale would be an analytic laboratory scale - not likely to be on some shooter's bench.
Interesting observation about the black stuff - most likely heavy metal residues from explosive primer compounds. I believe almost all of the back residue cleaned out of rifle barrels is not carbon.
Visual inspection of zillions of primers might cause some psychologic impairment.
Ned Ludd
Silver $$ Contributor
Balances with 0.1 mg readability, which usually means accuracy in the ~0.2 mg range, are not unheard of in the reloading game, but can be pretty pricey. I have a very nice Mettler analytical balance that can be set to 0.1 mg or 0.01 mg readability and have used it to weight-sort a box of Fed 205 primers. My intention is compare velocities obtained with two groups of 10 primers each representing the highest/lowest regions within the overall range, although I haven't actually done the velocity test as yet. The overall weight range for 100 primers spanned only 6.9 mg (0.2340 g to 0.2409 g), so a balance with 1.0 mg readability would not be satisfactory for this purpose.
Although some of the black residue deposited in the barrel after shooting is certainly due to primer components, it is unlikely that it represents more than a small fraction of the total. The median weight value of the small rifle primers I checked was 0.2375 g, or about 3.7 gr, which also includes the weight of the cup and anvil and is consistent with Dave's weights posted above in this thread. Dave's data indicate that the average weight of priming compound that was combusted and actually left the cup/anvil was ~0.022 g, or about 0.34 gr. Thus, the weight amount of priming compound would typically represent well below 1.0 % of a typical .308 Win powder charge weight, for example. I can't state with certainty exactly what percentage of the residue we refer to as "carbon" is actually carbon (as opposed to metals), but it's very likely that a large portion of it is coming from combusted powder.
The study/inquiry that I quoted actually measured primer blast waves using transducers. Some analysis, using velocity as an indicator of primer strength variability, would include any number of other variables included in the shooting process. An analysis using 10 samples on each side of minimum or maximum primer weight derived from bullet velocities would also include the many variables included in the shooting process.
A typical cartridge powder charge might be 100's of times greater than with weight of a tiny primer charge containing an heavy metal explosive compounds. Upon combustion the nitrocellulose powder is largely converted into carbon dioxide and carbon monoxide gasses. Incomplete nitrocellulose combustion to a very small degree might occur. Some of the remaining compounds include salts of various metals. These residue products are not carbon, an element. Making an assumption to determine residue source and labeling this as "carbon", based on the huge disparity of unexploded primer compound weight to un-combusted smokeless powder might not be valid as the products of the nitrocellulose combustion are almost all gaseous and non-carbon.
What would visual inspection of primers entail? Would the primers be placed on some conveyor belt anvil side up for some inspector to search for unacceptable disparities like crooked, under/over protruding anvils or incompletely formed cups? Would the inspection quota or demand be measured in time or primers? Federal packages their primers much differently than CCI and I can see how this could reduce chain reaction explosions. Did Federal experience any event causing them to package primers in a markedly different and probably more expensive way than CCI?
Nice photos!
dcali
Bullet Maker
While not totally worthless, read Courtney's "papers" with a critical eye. This one in particular is sloppy when compared to stuff that was done in the 70s. Why they'd spend all that money and not do it right is beyond me. Courtney is a creative and smart guy, but runs experiments on a shoestring budget, are generally not peer reviewed, and it shows.
Ned Ludd
Silver $$ Contributor
That particular paper of Courtney's was rendered essentially invalid because of the low resolution of his balance.
Simply switching powders without changing primers can result in a huge difference in the amount of soot left in the barrel, again suggesting it is largely due to incomplete combustion of the powder, not the priming compound. Powders such as Varget and H4895 leave a huge amount of residue as compared to something like a comparable weight of N140. It would be pretty easy to test how much the black soot left in a barrel was due solely to priming compound by firing a case that contained nothing more than a primer, as Dave did in the OP, running patches through until they were no longer black, then repeating the same approach with a loaded round. Clearly primers are responsible for some of the residue left behind in the barrel. But I suspect the powder itself is also a contributing factor.
Last edited:
dcali
Bullet Maker
A far better way to have spent his time and money would be to
a) Use a proper fixture instead of a rifle (essentially a small pressure vessel, vented or not) so that you can repeat the results. This is basic science. A good fixture has even been designed- a quick search of literature on primers would have turned up a paper that details it. This paper gets constantly cited, and is very good: Kuo, K.; Moore, B.; Chen, D. Characterization of Mass Flow Rates for Various Percussion Primers; Gasdynamics of Detonations and Explosives; J. R. Bowen, N. Manson, A. K. Oppenheim, R. I. Soloukhin, Eds.; AIAA Progress Series, Vol. 75, 1981, pp 323–337. Unfortunately to mke the most of it, you need to know the chemical composition of the priming compound, which is not available outside of the military primers. But at least getting consistently obtained pressure vs time charts for primers is very doable.
b) Use a scale that's good enough. Again, basic science.
c) Verify that the priming compound is the source of the weight variation rather than just use total weight.
d) USE ALL AVAILABLE COMMERCIAL PRIMERS. This is the most ridiculous thing he skipped. A comprehensive ranking of primer energy would actually be valuable. To be fair, he does make an attempt at a ranking, but only in a half assed way.
And that's just off the top of my head. I don't even know if there are other issues - getting those transducers to not lie to you is not always trivial either.
Ned Ludd
Silver $$ Contributor
To his credit, Mr. Courtney clearly points out the limitations of the balance used. Within the confines of using total primer weight, a 1 mg readability (~2 mg resolution) balance would probably be more than sufficient. However, it was the difference in total mass between primers that was attributed to differences in the mass of priming compound, which is a much smaller figure. The study would have certainly benefitted from the use of a higher resolution balance.
Nonetheless, my belief is that a statistically significant number of velocity measurements is the best readout for such a test. There is no good reason to use a more sensitive readout in light of other limiting factors such as balance resolution. If a reliable chronograph cannot detect a significant difference in velocity between primers of varying mass given a sufficient number of samples, then it is pointless to suggest that any difference observed on the target would be statistically significant either.
By analogy, I have observed that case weight correlates relatively well with internal volume. For .223 Rem cases, the difference between the heaviest and lightest cases within a single Lot# can easily be shown to cause velocity variance of as much as 20-25 fps, a value readily detected with a good chronograph. Likewise, if the heaviest and lightest primers within a Lot# are capable of causing a noticeable difference on the target, one would expect to be able to detect the difference at the velocity level. If any velocity difference was so small as to escape detection with a good chronograph, it would be very difficult to explain exactly how any difference observed on the target was related to a difference in primer mass. Thus, it would seem as though using measured velocity would be the much simpler approach to testing primers for correlating any relationship between primer mass and performance. I'm not really clear on why Mr. Courtney went the transducer route with this work.
Nonetheless, my belief is that a statistically significant number of velocity measurements is the best readout for such a test. There is no good reason to use a more sensitive readout in light of other limiting factors such as balance resolution. If a reliable chronograph cannot detect a significant difference in velocity between primers of varying mass given a sufficient number of samples, then it is pointless to suggest that any difference observed on the target would be statistically significant either.
By analogy, I have observed that case weight correlates relatively well with internal volume. For .223 Rem cases, the difference between the heaviest and lightest cases within a single Lot# can easily be shown to cause velocity variance of as much as 20-25 fps, a value readily detected with a good chronograph. Likewise, if the heaviest and lightest primers within a Lot# are capable of causing a noticeable difference on the target, one would expect to be able to detect the difference at the velocity level. If any velocity difference was so small as to escape detection with a good chronograph, it would be very difficult to explain exactly how any difference observed on the target was related to a difference in primer mass. Thus, it would seem as though using measured velocity would be the much simpler approach to testing primers for correlating any relationship between primer mass and performance. I'm not really clear on why Mr. Courtney went the transducer route with this work.
My guess is that Dr. Courtney (PhD, Physics, MIT) wanted to remove variables that are involved with the cartridge load process that would affect velocity. By using a transducer to measure the actual psi/mg, all the attendant load stuff would be skipped and an actual evaluation of primer consistency would be determined by measurement of blast pressures. Table 2 shows a bunch of primers were weighed to within .1 mg, total mass and pressures. Pressure tests using total primer mass (fig. 3) and mass loss by detonation for Fed. 210M primers, (fig. 4) were shown with weights to .1 mg. I think the study was aimed at shooters rather than engineers/scientists. If Dr. Courtney conducted this study using any grant or public funding budget considerations would be in effect.
Low velocity spreads would introduce the entire load process and environmental factors into consideration. My thinking is that velocity consistency would not be greatly affected by minute primer explosive charge variations measured in .1 mg increments because of the tiny quantity of the primer action compared to the entire load process. I liked the study, in part, because I could easily understand it and other confusing and unnecessary factors were omitted.
All this fussing over primers would be sort of negated should the carefully selected primers produce vertically strung groups ("observed on the target") having low velocity spreads and standard deviations.
dcali
Bullet Maker
I think the pressure transducers are a good approach. At least it’s the best we can hope for outside of the manufacturers giving us what I’m sure they view as proprietary info. The trouble with this experiment that is hard to get around is that a good percentage of primer energy is in the form of high energy (hot) solids/liquids, and not gasses. Solids will not show up on a pressure graph because they are incompressible and small, so a higher energy primer with a lower gas content will show up as having lower energy than it actually has. This method basically ignores a significant portion of primer energy. The only way around this that I know of requires knowing the chemical composition of the priming mixture, which is proprietary.
What we are after may or may not show up as velocity. Or at the very least, adding the additional variables of an actual firearm, bullet and powder, are going to muddy the conclusions. At the end of the day, we’re trying to figure out ignition consistency, so I think it’s helpful to isolate the primer output as much as we can.
The trouble is that Courtney half assed it and his data is only useful as a comparison to itself because of the way he did it. It was a reasonable effort - I’m not trying to bag on the guy. But you wouldn’t find a serious study using a rifle rather than a test fixture, for example.
But starting over with a good experiment using similar methods would be a worthwhile exercise. It’s not going to tell us everything because of the solid vs gas issue, but it may be helpful, especially to the extent that different manufacturers use similar mixtures. I think this could be done for less than $10k. The pressure transducers and the means of reading them are pretty pricey, but the fixture is small and basically the size of a rifle camber. A decent machinist could make one no problem. That’s really all you need.
What I would love to see is these pressure traces and primer compound weights for all the usual primers, ranked so that we can start to draw some conclusions about which primers to use. At least then we’d have some idea of which direction we are going in when changing primers.
I’m not sure it’s possible to do much better than that without help from the manufacturers.
What we are after may or may not show up as velocity. Or at the very least, adding the additional variables of an actual firearm, bullet and powder, are going to muddy the conclusions. At the end of the day, we’re trying to figure out ignition consistency, so I think it’s helpful to isolate the primer output as much as we can.
The trouble is that Courtney half assed it and his data is only useful as a comparison to itself because of the way he did it. It was a reasonable effort - I’m not trying to bag on the guy. But you wouldn’t find a serious study using a rifle rather than a test fixture, for example.
But starting over with a good experiment using similar methods would be a worthwhile exercise. It’s not going to tell us everything because of the solid vs gas issue, but it may be helpful, especially to the extent that different manufacturers use similar mixtures. I think this could be done for less than $10k. The pressure transducers and the means of reading them are pretty pricey, but the fixture is small and basically the size of a rifle camber. A decent machinist could make one no problem. That’s really all you need.
What I would love to see is these pressure traces and primer compound weights for all the usual primers, ranked so that we can start to draw some conclusions about which primers to use. At least then we’d have some idea of which direction we are going in when changing primers.
I’m not sure it’s possible to do much better than that without help from the manufacturers.
Ned Ludd
Silver $$ Contributor
Variables introduced by hand-loading cartridges affect velocity. This can never be avoided the real shooting world, so why use a method to evaluate primers that avoids such variables? It is meaningless to use a readout that has no demonstrable relation to accuracy/precision on a target. In contrast, velocity has a clear link to accuracy/precision.
As far as balances go, I learned quite a bit about them when I received my PhD in Biochemistry and Molecular Biology at Purdue University. Courtney specifically stated that he used an Acculab VIC-123 balance for this body of work. I downloaded the user's manual some time ago when I first became aware of this article, to determine whether it might be a limiting factor in the methodology employed. Courtney reported in this paper that the balance used has 1 mg readability, but that is misleading because it only has +/- 3 mg linearity, which is a better measure of the balance's capabilities for this purpose. Readability is simply the number of digits displayed on the screen and has nothing to do with the actual accuracy/precision of the balance.
Further, the values in Table 2 or elsewhere in the paper were not "weighed to within 0.1 mg". Those are averaged values reported to number of significant digits that were simply not justified based on the equipment used. That is the major flaw that invalidates the entire work, IMO. He used a balance only capable of determining mass to +/- 3 mg, and reported the average measurement to a resolution far higher than which the instrument was actually capable. In more simplistic terms, the scale can't actually weigh what they claim it weighed. Identification of limiting sources of experimental error and spotting methodological discrepancies are something I also learned ad nauseum while in graduate school.
The readers of any published scientific report deserve to have confidence that what they are reading actually is scientifically valid. That is one reason why many upper tier journals use a peer review process. I have seen quite a few claims that primers can be weight-sorted to improve precision. If someone makes the claim in a post at an online shooting forum, whether with or without supporting data, well, you just have to take what you get and decide whether to believe it or not. If it is a published report, the authors have measure a responsibility to ensure that the conclusions are fully supported by experimental evidence. Given the number of competitive shooters in this country and elsewhere, the notion that primers can be weight-sorted is NOT a trivial one. In fact, given the cost, time, and effort many of us put into the sport, I'd say it's far from trivial. I would very much like to believe that weight-sorting primers can make a difference, but I'm not there yet, partially because of such unsupported claims as have made in this paper and elsewhere.
dcali
Bullet Maker
The reason you want to separate out the primer is because there’s more than one thing we can learn here. One is “does weighing primers matter?”. The other is “is this a mild or heavy duty primer?”
It should be relatively straightforward to characterize existing primers in a way that lets us choose them purposefully rather than just trial and error. I think if you answer this question, you will have gone a long way towards answering the weight variation question, simply because you will have measured a ton of them and will have a feel for variability. You will then have some knowledge to go and think about things like load density, case shape, and powder-primer interactions.
In other words this is step one down a rat hole that goes deep. I have looked for good info on ignition and as far as I can tell, it doesn’t really exist for our needs. There is a lot of hand waving, punting, and “it’s good enough”. I’m not sure it is good enough. Not when we’re try to shoot 1” groups at 1000. There’s still a lot we don’t know.
It should be relatively straightforward to characterize existing primers in a way that lets us choose them purposefully rather than just trial and error. I think if you answer this question, you will have gone a long way towards answering the weight variation question, simply because you will have measured a ton of them and will have a feel for variability. You will then have some knowledge to go and think about things like load density, case shape, and powder-primer interactions.
In other words this is step one down a rat hole that goes deep. I have looked for good info on ignition and as far as I can tell, it doesn’t really exist for our needs. There is a lot of hand waving, punting, and “it’s good enough”. I’m not sure it is good enough. Not when we’re try to shoot 1” groups at 1000. There’s still a lot we don’t know.
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.