Vertical Dispersion - Weighing Primers

[Ray123]

I don't weight primers, and all those who do, go on and continue doing so.
But it seems that you're weighing variables, that you have no control over...there are primer cup weights variations, primer mixture weights and consistency variations, and primer anvil weights variations, each one a variable, and inconsistent to the next... so you're not just measuring the amount of primer mixture.. and its active ingredients...and the active ingredients in the mixture are constantly varying from primer to primer...So you have no idea of what the total weight is actually measuring. Unless you assembled the primers yourself...and separately weigh each component to your tolerance then assembled them, you'd have an idea of what you're measuring, but there will still be variations, however so small as your tolerances allow then there is the mixture variation, not only weight but chemical composition, in total molecular consistency.
So, I see it as fruitless endeavor for me...but it might help you, if primer assembly weights vary widely in your batch of primers, for a physical or mental edge, ...if it just makes you feel better...weigh away.

 

[Rocketvapor]

I'll will have to scan back and find that report that shows almost no pressure to mass correlation with CCI 450 primers. Just seems strange for one type of primer tested when all others had a much higher psi/mg slope.
"

 

[Mulligan]

For those that do weigh primers, which unit of measure do you prefer
Grams
Grains
I’m leaning towards grams..
Jim

https://forum.accurateshooter.com/attachments/primer-test_weight-sorting-srp-6ppc_1-pdf.1070719/

Jim,
I have used both, grains is an easier unit of measure for me think about…ponder. My scale is more comfy with grams. I believe the scale is a touch more precise when viewing the results in grams vs grains. Therefore, I now mostly use grams.
CW

edited to include link to the original thread with lots of colorful opinions.

How much "Extreme Spread" is acceptable in competition?

A little background, This is in regards to a thread I read on this forum regarding weight sorting primers. I have attached a short article describing a quick test I performed to see if a real test is warranted. In the attached "quick test"- The average MV from the lightest 5 primers (actually...

forum.accurateshooter.com

CW

 

[PigButtons]

@Dave M.
Sort until you have an obvious normal distribution of weights.
Take 10 low outliers and 10 high outliers, and the rest from NEAR the mean.
If outliers weighed to the nearest milligram don't show any benefit, weighing to 0.1mg surely won't.
Load your 70 or so rounds for your 600X3 isolating the ten low and 10 high for your second relay.
Ex: Sighters from mean weight, relay one from mean weight, first 10 of relay 2 low outliers, second 10 of relay 2 the high outliers. Shoot relay 3 from the mean weight primers.
All same day, almost the same environment, same reloading batch, same you
Post scores.

One hint for those without a precision lab balance, or just to save a few seconds per primer:
Tare the scale then add a 1 gram check weight to the scale.
Will indicate 1.000g without a primer and 1.350g (or so) with a primer.
Milligram resolution should show outliers. With a milligram indicating scale the +/- half count rollover will be hidden. Range of weight, high to low should be a FEW milligrams. You are only looking for outliers.

With a 1g base, DRIFT and REPEATABILITY will be instantly visible.
Auto zero of balance won't be triggered. At a very small measuring range (light to heavy primer) scale LINEARITY will NOT be a factor. Full scale calibration, percentage based, will NOT be a factor except in the WORST conditions. The 1.000g will monitor every weight performed. If it drifts, remove the check weight, tare, add the check weight.
This 1.000g check weight is a continuous IN PROCESS check.
If you don't trust the process, reweigh the lowest and heaviest outlier after sorting.
Red and green markers in the case groove to track outliers in case you spill the box

You Sir, are a man that has made being OCD an advantageous character trait.

 

[CharlieNC]

I'll will have to scan back and find that report that shows almost no pressure to mass correlation with CCI 450 primers. Just seems strange for one type of primer tested when all others had a much higher psi/mg slope.
"View attachment 1324360

Depends on the degree of weight variability, was this just a uniform lot? Are all of these just a snapshot at a point in time? These results are convincing that weight matters, but far from characterizing which brand is best over the long haul.

 

[JFrank]

To accompany my gram weighed primers I have lightly cleaned the primer pockets with my 21st century micro adjust uniformer set at just shy of .127, then seat the .122 primer at .009 below flush using a micro click adjustable 21st century hand primer I can get a repeatable .004 crush, with a witness mark on the seater I can test plus or minus / better or worse with results printed on paper at 500 yards, all in my effort to clean up my ignition a bit and hopefully trim my 1 k aggs.
I may not see a difference but at least I have assigned a number to the process .

 

[BoydAllen]

The differences between different primers may affect tune requiring some degree of tuning for each to discover its true accuracy potential. Most primer tests that I have read ignore this.

 

[Dave M.]

Wishing you and the Ex the best.

I don't get many opportunities to just test loads @ 600 so I slip in a 10 or 20 round string in the middle of the 60.
I now weight my powder charges in grams with a 10.000g Continuous In process Check weight.

Doesn’t work with an autothrow system though, correct?

 

[Rocketvapor]

@Dave M.
I don't have an autothrow system.
Might be able to fudge target charge.
Zero, add check weight, charge to a total that is charge Plus check weight??
If you trust your weighing equipment then extra monitoring isn't needed but I still read threads about weighing problems with drift or static being issues with accuracy even with really good systems.

I downloaded the pdf of the primer test.

I'm a run of the mill F-Class shooter still trying to Master 600 before moving on to 1000.
My equipment is only capable of beating me. That's the goal. Do better next time.
Won't win but it's gonna be a long ride home if a 22N in F-Open beat you
The closest 600/1000 meet is on the last Saturday of the month. Looks like April.
The wife and I need a couple trigger sessions at a closer 100yd range before then.

 

[Webster]

Hey Guys,

I'm not looking to start a debate on the merits of weighing primers, or if it's worth the time investment. I've already decided to give it whirl, and I've weighed out 1,000 of them into groups separated by .02gr mostly (with some extreme outliers culled entirely).

I will say I was pretty surprised by a couple of observations. First, there was way more variation than I was expecting to find. I had a range from 2.28gr all the way up to 2.52gr. Most fell right around 2.40-2.46gr; nice little bell-curve.

It's not my intent to mix any weight groups; just going to load all those that weighed the same together.

That said, I'm not going to get a chance to shoot these until my next match, but as of late I've been struggling a bit with vertical in my load. It'll hold 10-ring vertical consistently at 1,000, but it's not as good as I see from some of the top guys.

I've played around with depth in .002 graduations, but can't seem to tune it any tighter, so here we are. I think my powder node is on point as I'm in the usual velocity range for my barrel length/bullet combo, and generally speaking the gun is shooting quite well.

My question: To those that have weight sorted primers, how much (if any) improvement in vertical did you see?

Bring on the discussion; my body is ready.

Components:
200.20X
N150
Lapua Plama - turned .014"
CCI 400s
.0015 'interference fit'
AMPed every firing

Never weighed primers. However I noticed if you look at the anvil side on some primers you can see the charging compound ozing out around the foil. Don't remember which brands but some anvils have stains on them and others are clean.

 

[Dave M.]

I shot this morning in a 600 yard competition. It was only two 20 round strings, so I had to change my approach for the experiment.
I’m shooting a 6 dasher with 1945 rounds on the barrel. 33.1g RL-15 with Berger 105g VLD Targets, CCI 450 primers, 3080fps MV, shooting .009” into the lands.

in Round 1, I used only primers from the same lot that had a mass of .237 grams (the median of 300 primers measured). All shots, including sighters, were from the .237 grams sorted group.

In round 2, I used 10 primers from the light end of the distribution (all had a mass of .233 or .234 grams) and 10 primers from the heavy end (all weighed .240 grams). I mixed up the high and low primer rounds in my 20 shots for record so I wouldn’t skew the data by knowing which were high or low mass primer rounds.

Round 1:
Light rain, 29.88” station pressure
Wind 5-9mph from 2-4 o’clock
200-13X
Vertical - 3.553” (0.566 moa)
Horizontal - 3.555” (0.566 moa)

Round 2:
Light rain, 29.882” station pressure
Wind 6-10mph from 1-4 o’clock
200-17X
Vertical - 1.707” (0.272 moa)
Horizontal - 4.850” (0.772 moa)

Oddly, the group with less vertical was shot with primers at opposite tails of the distribution. I guess weighing primers has very little effect. I can’t see any value in weighing CCI 450 primers. This is the same conclusion the authors of the previously referenced military article came to regarding #450 primers. Zero correlation.

The wind was a little more switchy in round 2 and that’s what I’d attribute the wider horizontal variance.
Note that in Round 1, all shots (including 13 sighters/foulers) has primers weighing .237 grams. The average velocity at the target was 1979fps with a 16.6fps SD.

In Round 2, shot with both high and low mass primers, had the exact same velocity at the target but only a 10.2fps SD

target pics:
Round 1:



Round 2 target pics:



Needless to say, I don’t see primer weighing or sorting in my future. Feel free to critique or ask questions.

Interesting study and I’m glad I did it. I suspect the results could be much different using other primer brands or models.

YMMV,
Dave M.

 

[RegionRat]

@Dave M. any idea of the year or batch of your primers, and if you have the actual stats on the weights would you mind sharing them? N, Avg, StDev?

Sometimes, the humans, tooling, and QC involved in making primers allow escapes. As much as I do not wish to see it again, there have been some from every brand over the years.

Nice shooting.

 

[Dave M.]

@Dave M. any idea of the year or batch of your primers, and if you have the actual stats on the weights would you mind sharing them? N, Avg, StDev?

Sometimes, the humans, tooling, and QC involved in making primers allow escapes. As much as I do not wish to see it again, there have been some from every brand over the years.

Nice shooting.

I didn’t enter them all into excel but feel free to do so from my crude graph of 300 primers sorted by mass. I suspect with 123 of them having a mass of .237 grams and almost as many pieces under that mass as there were over, that the average would be darn close to .237. It seemed very close to normally distributed.

 

[RegionRat]

Many thanks @Dave M.
It looks like a good batch based on your results and weights.
Those were two great strings you shot, did that win your match?

 

[Dave M.]

Many thanks @Dave M.
It looks like a good batch based on your results and weights.
Those were two great strings you shot, did that win your match?

I did win. I keep thinking this barrel is going to drop off soon (pushing 2000 rounds now), but it just keep hammering and seems to be getting better with age. Funny thing is that it doesn’t seem to like to be cleaned very thoroughly, gentle cleaning after each match. If it’s cleaned deeply, it will take 20-30 rounds to settle back in.
dave

 

[INTJ]

For those that do weigh primers, which unit of measure do you prefer
Grams
Grains
I’m leaning towards grams..
Jim

I sort them in .05 grain groups, on a Sartorius that measures to .001 grains

 

[INTJ]

To accompany my gram weighed primers I have lightly cleaned the primer pockets with my 21st century micro adjust uniformer set at just shy of .127, then seat the .122 primer at .009 below flush using a micro click adjustable 21st century hand primer I can get a repeatable .004 crush, with a witness mark on the seater I can test plus or minus / better or worse with results printed on paper at 500 yards, all in my effort to clean up my ignition a bit and hopefully trim my 1 k aggs.
I may not see a difference but at least I have assigned a number to the process .

If you use the K&M Primer Gauge then you don't have to measure every pocket and measure every primer cup height. The Gauge does that as part of the primer seating process.

 

[Bc'z]

If you use the K&M Primer Gauge then you don't have to measure every pocket and measure every primer cup height. The Gauge does that as part of the primer seating process.

Blaine are you uniforming pockets?

 

[INTJ]

I shot this morning in a 600 yard competition. It was only two 20 round strings, so I had to change my approach for the experiment.
I’m shooting a 6 dasher with 1945 rounds on the barrel. 33.1g RL-15 with Berger 105g VLD Targets, CCI 450 primers, 3080fps MV, shooting .009” into the lands.

in Round 1, I used only primers from the same lot that had a mass of .237 grams (the median of 300 primers measured). All shots, including sighters, were from the .237 grams sorted group.

In round 2, I used 10 primers from the light end of the distribution (all had a mass of .233 or .234 grams) and 10 primers from the heavy end (all weighed .240 grams). I mixed up the high and low primer rounds in my 20 shots for record so I wouldn’t skew the data by knowing which were high or low mass primer rounds.

Round 1:
Light rain, 29.88” station pressure
Wind 5-9mph from 2-4 o’clock
200-13X
Vertical - 3.553” (0.566 moa)
Horizontal - 3.555” (0.566 moa)

Round 2:
Light rain, 29.882” station pressure
Wind 6-10mph from 1-4 o’clock
200-17X
Vertical - 1.707” (0.272 moa)
Horizontal - 4.850” (0.772 moa)

Oddly, the group with less vertical was shot with primers at opposite tails of the distribution. I guess weighing primers has very little effect. I can’t see any value in weighing CCI 450 primers. This is the same conclusion the authors of the previously referenced military article came to regarding #450 primers. Zero correlation.

The wind was a little more switchy in round 2 and that’s what I’d attribute the wider horizontal variance.
Note that in Round 1, all shots (including 13 sighters/foulers) has primers weighing .237 grams. The average velocity at the target was 1979fps with a 16.6fps SD.

In Round 2, shot with both high and low mass primers, had the exact same velocity at the target but only a 10.2fps SD

target pics:
Round 1:
View attachment 1326111
View attachment 1326112

Round 2 target pics:
View attachment 1326113
View attachment 1326114

Needless to say, I don’t see primer weighing or sorting in my future. Feel free to critique or ask questions.

Interesting study and I’m glad I did it. I suspect the results could be much different using other primer brands or models.

YMMV,
Dave M.

Shooting 20 round groups F-Class style will not likely show the effect of primer weighing or getting an exact primer crush. The conditions will overwhelm the results. From that it is easy for an F-Class competitor to conclude primer weighing is of no value for F-Class, and I would agree.

I am not even sure 1000 yd 10-shot groups shot from an LR BR heavy gun would show any advantage to primer weighing, because again, conditions may well hide it.

I do think there are a couple of ways to see if there in any advantage to weighing primers.

One is to shoot five shot groups BR style (single feed as fast as you can) in excellent conditions. That is where we see 1000 yd 5-shot BR groups under 2". If primer weighing is an advantage it might show up here. The issue is finding excellent conditions to shoot in.

Another way, the one that I think is the most useful, is to see if the ES of your loads tightens up with weighed primers. Now we all know the tightest ES rarely produces the tightest groups, and ES isn't a goal. However, I think it can be an indicator of the quality of our loading practices.

For example, when I started using the K&M Primer Gauge--which allows me to seat each primer in each primer pocket to an exact crush, my 5-shot ES the best loads for my 6 BRA went from low teens to high single digits. To me, that validated to worth of the tool.

Now while I have shot smaller groups at 1K since using that tool, most of that has come from better tuning on my part. However, the 5 FPS improvement may indeed make a difference with even a well-tuned load.

We know that a well tuned load will shoot to the same POI over a 20-30 FPS velocity variation. We also know that there is velocity variation with each shot. Even if each round was loaded exactly the same, we will still see velocity variation. If we can reduce velocity variation by 5 fps because of something we did with primers, it will be easier to stay within the node. It will be more forgiving concerning all the things that affect velocity.

I'll not likely ever know if how I process primers made a difference on a given target. However, it is relatively quick and easy to do and I know it makes my loaded rounds more consistent. That can't do anything but help.....

 

[INTJ]

Blaine are you uniforming pockets?

Yes, but I am not convinced we can get them better than say .001". I do routinely see up to .004" of variation from the combined pocket depth variation and primer cup height variation. I have not measured pockets separately, because the K&M Primer Gauge takes care of all that as part of the primer seating process.