Keith Glasscock
Gold $$ Contributor
Just adding a little context here. The primers you are weighing matter.
Some brands have processes that cause weight variance that does not correlate to differences in priming compound weight. This creates noise in any test that will frustrate an attempt to make sense of the primer weight to velocity (i.e. Fed 210M red blob).
Other brands have large variations in the weight of the metal components that frustrate attempts to identify differences in priming compound weight (i.e. Wolf KVB-7).
Other primers are really clean without those noise factors. Those primers show a definite correlation between average velocity and primer weight (i.e. CCI BR2).
For example, on my 284, weighing primers resulted in a 12 fps difference in average velocity between the lightest and heaviest primers. ~1 to 2 fps per mg.
Based on your ES/SD to start, the difference could be almost impossible to reliably measure. Here is a process variation model (RSS) that can help to understand the implications of tolerance stacking:
ES of 20 (starting): Sqrt(20^2 - 12^2) = 16. In this case, the average ES for many, many trials would be reduced 20%. Given the general variability of tested ES values, testing by ES is at best unreliable, and at worst self-deceptive.
(Using 25% of the measured ES for assumed SD input)
SD of 5 (starting): Sqrt(5^2 - 3^2) = 4. In this case, again the SD changes 20%.
On the other hand, if your ES and SD are already this low, the question remains whether you would be better off weighing primers or learning how to shoot the rifle better?
Let's take a little different situation, that some shooters face. Will weighing primers help with my excessive ES/SD?
ES of 30: Sqrt(30^2 - 12^2) = 27.95. In this case, the ES reduced just 7.3%. While there is a reduction, it is so small that with less than huge sample sizes (200+ shots), there is a better than even chance that it will appear that the ES is worse rather than better. The answer is simply, no, it isn't the cause of your high ES.
SD of 10: Sqrt(10^2 - 3^2) = 9.53. Once again, this would be all but undetectable in any reliable way with sample sizes smaller than entire barrels worth of wasted components. Again, it isn't going to fix your high SD numbers.
In my opinion, sorting primers has a positive effect on velocity variation and vertical distribution at long range (1k yards), but that effect can only be identified through multiple seasons of shooting, not one test of 20, 40, or 100 shots.
There are lots of factors that have a much larger impact of velocity variation. Until you get to the pinnacle of good velocity variation numbers, I wouldn't bother with weighing primers, and then only to maintain an existing advantage, not to try to catch up with the shooters that are beating you match after match.
Some brands have processes that cause weight variance that does not correlate to differences in priming compound weight. This creates noise in any test that will frustrate an attempt to make sense of the primer weight to velocity (i.e. Fed 210M red blob).
Other brands have large variations in the weight of the metal components that frustrate attempts to identify differences in priming compound weight (i.e. Wolf KVB-7).
Other primers are really clean without those noise factors. Those primers show a definite correlation between average velocity and primer weight (i.e. CCI BR2).
HERE IS THE TRUTH:
Just because primer compound weight differences make an X difference in average velocity, that does not mean that sorting out that variation is going to reduce the ES by that amount. Instead, you will get the root-sum-square (RSS) difference in velocity variation. That variation will take extremely large sample sizes to reliably identify (think barrels not shots).For example, on my 284, weighing primers resulted in a 12 fps difference in average velocity between the lightest and heaviest primers. ~1 to 2 fps per mg.
Based on your ES/SD to start, the difference could be almost impossible to reliably measure. Here is a process variation model (RSS) that can help to understand the implications of tolerance stacking:
ES of 20 (starting): Sqrt(20^2 - 12^2) = 16. In this case, the average ES for many, many trials would be reduced 20%. Given the general variability of tested ES values, testing by ES is at best unreliable, and at worst self-deceptive.
(Using 25% of the measured ES for assumed SD input)
SD of 5 (starting): Sqrt(5^2 - 3^2) = 4. In this case, again the SD changes 20%.
On the other hand, if your ES and SD are already this low, the question remains whether you would be better off weighing primers or learning how to shoot the rifle better?
Let's take a little different situation, that some shooters face. Will weighing primers help with my excessive ES/SD?
ES of 30: Sqrt(30^2 - 12^2) = 27.95. In this case, the ES reduced just 7.3%. While there is a reduction, it is so small that with less than huge sample sizes (200+ shots), there is a better than even chance that it will appear that the ES is worse rather than better. The answer is simply, no, it isn't the cause of your high ES.
SD of 10: Sqrt(10^2 - 3^2) = 9.53. Once again, this would be all but undetectable in any reliable way with sample sizes smaller than entire barrels worth of wasted components. Again, it isn't going to fix your high SD numbers.
In my opinion, sorting primers has a positive effect on velocity variation and vertical distribution at long range (1k yards), but that effect can only be identified through multiple seasons of shooting, not one test of 20, 40, or 100 shots.
There are lots of factors that have a much larger impact of velocity variation. Until you get to the pinnacle of good velocity variation numbers, I wouldn't bother with weighing primers, and then only to maintain an existing advantage, not to try to catch up with the shooters that are beating you match after match.