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Questions about primer sorting

drop_point

Silver $$ Contributor
I see that many are showing notable results from primer sorting. I've been skeptical of it myself, but I think I may give it ago to see if I can make any notable improvement on my next barrel.

When you sort, are you mixing lot numbers and maintaining a specific target weight for a batch of ammo? Or do you sort by lot and weight?

I ask because the primers I use have not only been expensive, they have been hard to find.
 
Probably the biggest benefit of "sorting" is isolating high/low outliers. Likely only a few.
Since there is a range of metal weight in the primers, fine sorting will have overlaps you can't find by weight.
The tests I performed were with High and Low weights, saving most of the middle weight primers for load development and competitions.
Just a guess, but with a small cartridge (I'm shooting a 22 Nosler) a weight outlier is a least 1/4 to 1/2 MOA off the waterline @ 600.
 
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Just to add some hints and suggestions for folks who have never participated in this kind of statistical sorting.

When starting out, it is hard to know what size sort bins to lay out. For starters, Rocketvapor's pointer to finding the mean or center of the average is a good one and the right place to start.

You will have to decide if you are going to run 50, 100, 1000, 2000, etc. for yourself. Just be aware you are sorting expolsive, and you must be very careful to handle primer as such. You are not sorting screws and nails, these things can and do go off when folks act silly or have accidents.

Treat live primers with respect and the greatest care to avoid ending up on the internet as a cautionary tale. There is a difference between deflagrant and explosive, so don't play around.

That said, the middle or average weight will be important so start by using at least 30 if not 100 like Rocketvapor says.

Then, if you have no other background with the specifics of your primers... once you have the average I will suggest the next steps based on 6 bins and you can always combine bins once you are done.

If you individually weigh and record the first 30, you can calculate a standard deviation (sample or population won't matter, use either one for now). Lay out six cups or containers in front of you with the average value in the middle and each cup being a bin with the size of the StDev value.

Real number values are messy, but to give you the picture say we have an average of 10.000 and a StDev of 1.00 to make it easy. You would run cups of 7, 8 ,9, 10, 11, and 12.

After your sort, you will find the most in the 9 and 10 cups, with many in the 8 and 11 cups, and fewer in the 7 and 12 cups.

In short, what we have done is to estimate a distribution based on a small sample of 30 pieces and estimated the size of a standard deviation. Normal Distributions can still have things show up past +/- 3 x StDev away from the average, but that is bad luck to find. The estimate is just that, an estimate, by the time you are done don't be surprised to find out reality is different or that the distribution is a little skewed.
 
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Weight for weight, primer compound counts for more than powder charge.

So a different way to think about the spread in primer compound weight would be to ask yourself if you would allow that much charge weight variation... by a factor.

The primer not only ignites the powder charge, but it participates in generating starting pressure that is contributing to the velocity all by itself.

The mean value of the primer compound creates ignition for the whole process, and the spread in the primer compound weight creates a variation that is just like the one from powder charge variation.

When your shooting gets to the point where you can see small differences in things like charge weight variation or neck tension, that is when you would consider primer weight variation.

Unless you have all those other variables under control and their noise is low enough, you don't benefit from weighing primers.

Just food for though.
 
Let's just say you are CLOSE to an MOA at 600/1000 yds.
Would spending a little time trimming 1/4 MOA off your groups caused by the few outlier primers be worth it? Do you travel to a match or a hunt?
Granted, there are those that shoot Cleans without sorting primers, think it's a waste of time, and don't see any benefit, but I see it on the target and that's enough for me.
If you don't care, then this isn't the thread for you.
The smaller the cartridge (or charge) the more primer weight might make a difference.

IF the best scale you can come up with is a milligram scale then sorting to 0.02 grains is plenty good enough. It's the outliers you are looking for.
The last brick I sorted came out to 366 grains per flat, 3.66gr average per primer.
I called anything outside +/- 0.04 grains an outlier and suitable for fouling rounds, pew-pew-pew practice rounds, or suitable for conducting a PRIMER TEST.
Here's one brick sorted. 3.67 gr average sorted to 0.04gr bins.
One-Brick.jpg

Light and heavy Ginex from one brick
Light-Heavy-Ginex.jpg

and WIN41. Tare empty flat, weight 100, light and heavy found in same flat.
Win41-Average.jpg
 
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"Let's just say you are CLOSE to an MOA at 600/1000 yds.
Would spending a little time trimming 1/4 MOA off your groups caused by the few outlier primers be worth it? Do you travel to a match or a hunt?"

Wow, 1/4 MOA group reduction from just over 1 MOA just by sorting primers? That is like a 25% reduction! Why aren't more shooters doing it?
 

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