Effect of primer weight on speed

[NamibHunter]

I realize there are several older threads on this topic. Many contain useful information, but there are Multiple contradictions as well. And not a lot of hard data. So: Decided to start a new thread.

Conducted a primer test for an MPA comp rifle in 6.5 CM. Hornady 140 ELDM projectiles, weight sorted FL sized Alpha brass, trimmed and fully prepped, a fairly high charge of H4350 (still below book max) weighed to 0.02 grain accuracy (one kernel of powder) via FX120i scale, while using CCI450 magnum small rifle primers, weighed on the same AND lab scale in milligram mode.

Brass was fully prepped and FL sized and shot well before. Alpha brass is thicker and has less internal capacity, but it has very consistent internal (water) volume, which ensures good reloading results.

My crony (LabRadar) results showed that primer weight has a measurable effect on MV: Primer weight ranged from 235 milligrams (3.63 grains) to 241 milligrams (3.72 grains). That 6 milligram (0.092 grain) range represents a 2.5% variation. The scale is accurate enough (to 0.02 grains or 0.001 grams = 1 milligram). It can pick up these small differences in primer weight. [As long as you prevent a draft: Close the door and turn off the AC. Btw: A standard powder scale with 0.1 grain resolution will not be very effective here.]

Collected 20 data points (threw out the first 3 ‘cold bore’ / fouling shots, which always tend to be slower). Assumed that three fouling shots are in fact sufficient. Data seems to prove this out. Fired rounds slowly and in random order, and barrel temperature was kept warm but not hot (around 120 degree F, via the temperature strip on the barrel). Luke warm barrel at all times, post fouling shots.

Then did a linear regression of the 20 data points. R-square is an indication of degree of fit, and in general that varies between 0 (no relationships at all) to 1.0 (perfectly correlated). A number like 0.7 or higher would be considered good. In this case, R-square was not particularly good, as it was only 0.23. Roughly indicating that my simple linear math model can only explain 23% of the variability in speed. So NOT a great model! [ironically: If i had a really bad batch of primers to work with that had much larger weight variation, my results would have been more convincing!]

Based on the model, speed increased by 11.5 fps over this narrow 2.5% range due to increased primer weight, or 2.33 fps per additional milligram of primer weight.

Note: Random ordered the cases, so speed results are not biased by a progressive increase in barrel temp, and kept the barrel temp lukewarm. Shot slowly from a sturdy steel bench, in a fairly constant 12 mph wind (fairly heavy wind, but direction was mostly constant).

Did not try to shoot separate groups for each weight range. The groups were shot at 100 yards, from a sturdy bipod, with an empty thick folded sports sock below the bag rider attached to the chassis. Group size varied between 0.35” and 0.65” with some horizontal deviation creeping into it due to lack of a proper sandbag (and not using free recoil). Yes i (slightly) pulled a few shots, mostly sideways, which increased horizontal deviation. Even so: Groups were adequate for what i do.

SD for all 20 rounds was 7.6 fps, which was suprisingly low given that i intentionally loaded ammo with the widest possible primer weight range. [Says a lot about the quality of this batch of CCI primers.]

If i could get a current BR champion to shoot these rounds in an underground 100 yard tunnel, i would have liked to report group size per 2 milligram weight range.... Any volunteers who own and operate a 100 or better yet a 300 yard underground tunnel, please let me know. ?

In short: The effect is real. Increased primer weight makes the bullet go faster. Other threads on this topic have already indicated (proven?) that the weight difference is all in the amount of explosive material inside the primer, not the metal components (primer cup or anvil).

Calculated how much SD would have improved if the effect of primer weight variation was completely removed: SD would have reduced from 7.6 fps to 6.7 fps for this group of 20 shots. Is that enough to worry about? Probably not.

How much of an effect does the primers actually have? For my rifle, powder, bullet and primer choice, i get 2.33 additional fps for each additional milligram of primer weight. Since primer weight increased by only 5 milligrams in this batch, or 2.3%, speed increased by only about 12 fps (or 0.4%). Not so much!

So should you weigh all your primers and sort them? Spend an entire week-end on this mind numbing task? [I did. It was boring as hell!]

OK: Trying to be serious and even handed here:

1) If you are competing for a BR championship or in an ELR event, and you are one win away from victory, then likely yes, you should at least consider weight sorting all your components, primers included. [Probably out of an abundance of caution.] In this scenario you are already getting ES under 10 and SD around 3 fps. So going up from 3 to 4 fps might cost you a point or two at 1000 yards.

2) If your SD is above 10 fps and ES is above 35 fps, the benefit of primer sorting will be minimal, assuming your batch of primers is as good or better than the one CCI batch that i tested. But how do you know for sure how good (or bad) your batch really is, unless you have already fired 30-100 rounds using this new batch, and your SD is holding close to your historical results? [Expensive way to determine primer batch quality.]

3) Recommendation: When you buy a new batch of 10,000 primers, do a random test and weigh 30-40 primers total from different boxes. Use a good scale with better than 0.1 grain resolution (0.05 gn or better). Compare the measured weight range (weight ES) to what you have historically considered adequate. Record the result in your reloading book. If it is about the same as before, STOP weighing primers and continue shooting them. If the new batch is significantly worse, say 2x or more, then get rid of that batch. Sell it to somebody who loads 200 yard hunting ammo.

My personal conclusion here is that i am going to do a quick check on new batches, and if they are good, i will not weight sort primers anymore. For what i do, there is not enough benefit in dropping SD by 0.9 fps.

If and when i get into the ELR game, i will weight sort primers again.

Namib

Sent from my iPhone

 

[NamibHunter]

Graph of muzzle velocity vs primer weight:

 

[NamibHunter]

Y-axis is muzzle velocity. X-axis is primer weight in milligrams.

Why milligrams? My FX120i scale has about 30% better resolution in gram mode compared to grain mode. So more accuracy.

 

[Greg Langelius *]

Excellent report. It confirm suspicions I've had for many years.

IMHO, the net takeaway is that the primer charge needs to be included as a portion of the overall charge driving the projectile.

For my simpler purposes, this sort of precision really can't be put to real usage. I can rely on factory QC and achieve my own goals.

But for other with more demanding goals, this correlation can help with things like ELR shooting, KYL, and any other applications (BR, etc.) requiring ultra precise accuracy.

Greg

 

[Sheldon N]

Interesting result. Props for shooting them in random order. Data looks solid.

I'm not going to sort primers myself, but this is good info to know.

 

[hlee]

Do it again, but this time keep track of what velocity goes with which cartridge case. Punch out the empty primer cups and weigh again. Report the data as a function of primer material, not primer cup + primer material. Did you weigh sort your projectiles? How consistent is your case volume? Finally, what is the precision of the magnetospeed? I mean, is 2760 really 2760, or could it be 2770 or 2750. There's a lot of variables, and primer weight seems to be a really small one. By your own admission "the fit only accounts for 23% of the variability." A better way to say this is that the fit is not supported by the data.

 

[NamibHunter]

Some of the groups shot during this experiment. All are 4 shot groups, even though they look like 2 or 3 shot groups. Most groups had 2 bullets through one hole, plus some scatter. One has 3 though one hole.

Horizontal deviation is partly my fault for not having taken along a sand bad that is small enough, and instead using an empty wool sock folded double. Bipod is most solid when the legs are extended at 45 degrees forward, and that puts it very low on the table. Much smaller sand bag is needed.

 

[NamibHunter]

Do it again, but this time keep track of what velocity goes with which cartridge case. Punch out the empty primer cups and weigh again. Report the data as a function of primer material, not primer cup + primer material. Did you weigh sort your projectiles? How consistent is your case volume? Finally, what is the precision of the magnetospeed? I mean, is 2760 really 2760, or could it be 2770 or 2750. There's a lot of variables, and primer weight seems to be a really small one. By your own admission "the fit only accounts for 23% of the variability." A better way to say this is that the fit is not supported by the data.

I was hoping for a better R square result... oh well!

Your idea is good: Primer weight was actually written on each case, and in the note book, and they have not yet been deprimed. So i could go the step beyond and look for the correlation with the primer material burned up when the shot was fired. That would take care of variations in cup and anvil weight. Should improve the results some.

Btw: Several folks have done exactly this, and they have all reported that the bulk of the weight variation comes from the primer compound. Not the metal components. But it would not hurt to take a second look at that!

Also, i wish i had access to a really bad batch of primers... Any ideas? If there was more variation in the amount of primer compound, the results would be less uncertain, and R square will improve some. Would like to see it above at least 50%.

Anybody who has a REALLY bad batch of SRP primers in a closet somewhere, who might want to donate them, PM me please!

You are correct that the crony will have errors of its own and contribute (possibly significantly) to the observed SD. Have compared MagnetoSpeed and LabRadar before, and they were a close match. Bryan Litz tested the SD (error level) of different cronographs. He gave a good score to the MagnetoSpeed, but did not test LabRadar (was likely not on the market at that point). I will have to look it up in his book, as i don’t recall the exact SD nr, but it was single digit.

Of course: A person will need lab quality equipment to determine the true SD of the LabRadar, so not an experiment i can run. I recall Litz used a crony with three screens spaced several feet apart.

I am hoping that the LabRadar is similar or better than MagnetoSpeed, because it uses multiple data points over the first hundred yards of bullet flight to back calculate bullet speed at the muzzle.... and radar system can be quite accurate. MagnetoSpeed has only one data point to work with (time delay between the two magnets).

But your complaint is valid: If my LabRadar has an SD of say 5 fps, then my true SD could be quite a bit lower than 7.6 fps, and i would not know it. From B Litz: Observed SD = square root ( (crony SD)^2 + (true bullet SD)^2). The biggest nr will always dominate, but you cannot get a smaller nr than the smallest of the two. Instrument SD imposes a lower limit on your result.

If i can speculate for a moment: I would be surprised if my delta MV nrs are off by more than 10 or 15 fps. There could well be a constant offset, but that would not matter here. Or so he hopes....

But yes. I need more variability in weight and speed to be definitive!

Somebody please send me a really bad batch of primers!

PS: Brass was actually weight sorted. Bullets were not.

 

[Sheldon N]

Somebody please send me a really bad batch of primers!

Technically can't mail primers easily, ORD-M hazmat classification.

 

[NamibHunter]

Technically can't mail primers easily, ORD-M hazmat classification.

Noted.

Anybody in Houston who wants to donate their worst ever batch of primers? SRP would be ideal, but not strictly a must.

Also, what brand of primers has the most variability? CCI was a little “too good”...

Namib

 

[NamibHunter]

Do it again, but this time keep track of what velocity goes with which cartridge case. Punch out the empty primer cups and weigh again. Report the data as a function of primer material, not primer cup + primer material. Did you weigh sort your projectiles? How consistent is your case volume? Finally, what is the precision of the magnetospeed? I mean, is 2760 really 2760, or could it be 2770 or 2750. There's a lot of variables, and primer weight seems to be a really small one. By your own admission "the fit only accounts for 23% of the variability." A better way to say this is that the fit is not supported by the data.

OK, here is the update:

De-primed all the cases, and weighed them all just now. Sadly, the relationship got worse, not better. I also know why: Some primers fell over and the anvil separated from the cup, and a lot of ash fell out. Others remained intact and very little ash fell out. That makes a big enough difference in the weight, enough to mess up any chance of fitting a better model. To make it work, you either have to keep all the ash in, or get rid of all the ash.

Next time, i will have to be a lot more careful, and either keep the primers intact, or intentionally separate anvil from cup, and clean them up with alchohol. Maybe bend the cup closed to prevent the anvils from falling out, and put them through an ultrasonic cleaner, while keeping them in order.

Sorry, tried my best!

 

[NamibHunter]

Update: Can confirm what many others have reported before: Primer weight differences are almost entirely caused by differences in the amount of priming compound, not the metallic components (cup or anvil).

Used a batch of CCI 450 Magnum SRP primers that i weight sorted before. Used the 237 milligram batch. Can confirm that carefully extracted and intact primers have very constant weight after firing. As long as you never turn them over and never let the ash fall out. Weighed the first 10 fired primers: 8 weighted 218 mg, and two were 219 mg. Could be scale rounding issues, or it could be a (very) small but real weight difference. On the edge of what the FX120i scale can do.

So it seems to me it is confirmed that the metal components have highly constant weight, and the priming compound can easily vary 2 or 3% (at least that was true in my particular batch of primers).

The load gave an SD of 8.5 fps and and ES of 32 fps for 38 rounds fired slowly over 2.5 hours. Ambient was 67 deg F. Strong 8-12 mph wind speed kept barrel lukewarm. Never hot.

Details of the load:

1. Used some of my previously sorted CCI 450 magnum small rifle primers that all weighed 0.237 grams (237 milligrams).

2. Loaded 38 rounds in 10x fired neck turned and weight sorted (1 grain range) Lapua brass, neck sized only in a Wilson hand die (it was FL sized one reload ago). Wilson micrometer seating die produces remarkably straight ammo: Concentricity is typically 0.5 to 1.5 thou. Applied mica dry lube to the bullet. [Seating action was jerky, which i know is not ideal. Feels like the pressure ring has to force its way past an obstruction. Donut due to bushing sizing only 2/3’rds of the neck?]

3. Bullet was a Berger 140 Hybrid, weight sorted into a batch of 140.0 (+- 0.05) grain. All from the same batch. Shot well before.

4. Powder was H4350 weighted down to a single kernel (corrected with a tweezer as needed), yes full-on OCD mode. No wind / fan / ac / draught allowed. Blocked the gap under the door to reduce airflow.

5. Seated with a superb Wilson seater with an Arbor press with seating force measurement. All Base to Ogive measurements were within 1.5 thou. Seating force varied between 30 and 65 lbs. More than i would like!

Conclusions:

If primer weight was a dominant reason for speed / MV differences, i would have expected a better SD, something closer to 5 or 6. Of course, if the LabRadar is indeed capable of such precision. TBD.

Admittedly, i am using a good batch and make of primers, and their weight range is only 2.5%. Still 2.5% is more than zero. But my seating force varied 100%. Maybe there is a clue in there... ?

Note that my prior batch (Alpha brass) had an SD of 7.6 fps when i intentionally used the widest possible range of primer weights i could find. Alpha has been fired 3x. [Too early for a donut to form?] This time i kept primer weight as narrow as possible, but the SD was slightly worse at 8.5 fps (compared to 7.6). Granted: Only one experiment, and different brass, different age, but at least in this particular case, there was no improvement in performance from weight sorting a good batch of CCI primers. [Other factors still dominate! Possibly case volume, or possibly the presence of donuts causing large seating force differences.]

My conclusions are the same as before:

1) Buy only good primers and confirm that you got a good batch. Easy to do, and that takes no time at all.

2) Once you have satisfied condition 1, there is not enough benefit in sorting primers if your SD is typically at 10 fps or above. Other factors need to be addressed first. [My SD are usually in the 8 to 12 fps range. Clearly, I have bigger problems than primer inconsistency!]

3) If you are aiming for ES below 10 (SD around 3 fps), and you are getting close, you should at least consider it. [Example: It might help you take an ES of 12-15 and get you down to 9-11 fps.] Small gain, and you have to decide if it is worth it or not.

For me it is “case closed”: I am not sorting primers anymore, until i get SD closer to 5.

BUT: Do what you believe is best for you. My situation is likely different from yours. Not trying to convince anyone. Just sharing hard data.

 

[hlee]

Your data doesn't support your conclusion. You had as high as 20 fps ES within a single primer weight, and a max ES of 32 across all weights. The primer weight v muzzle velocity is a shotgun pattern, and by your own observation, the data do not support the linear fit. The variability in the data is dominated by factors other than primer weight. And, the ability to achieve single digit ES without primer sorting belays the contention that primer weight has an effect large nough to worry about.

 

[47guy]

try some Fed205ms...450s have given me the worst ESs every time i try them the last few years and the BR2s are not much better.
fed205Ms always produce the best accuracy/consistence and numbers for me in both a 6BR and BRX

heres 55 rounds over the magneto speed...

 

[NamibHunter]

try some Fed205ms...450s have given me the worst ESs every time i try them the last few years and the BR2s are not much better.
fed205Ms always produce the best accuracy/consistence and numbers for me in both a 6BR and BRX

heres 55 rounds over the magneto speed...View attachment 7175857

Your SD is impressive sir. I will try Federal next.

Picked the magnum primer because it supposedly has a harder cup. Berger factory ammo had three pierced primers in the MPA rifle, and very pronounced craters. Was also fairly fast for a 6.5 CM (around 2840 fps). MPA cuts their chambers rather tight.

 

[47guy]

ive shot more then i can remember 0 1 and 2FPS 5 shot groups...i shot a 65x47 and had a 10shot group that had a 1FPS ES...ive had only 1 40+ shot sample that was 15FPS every other large sample has been 18FPS + and most end up around 20-25ish...theres always the one fucker shot that screws it up.

 

[47guy]

Your SD is impressive sir. I will try Federal next .

Picked the magnum primer because it supposedly has a harder cup. Berger factory ammo had three pierced primers in the MPA rifle, and very pronounced craters. Was also fairly fast for a 7.5 CM (around 2840 fps). MPA cuts their chambers rather tight.

are you shooting a 6 or 65?..small firing pin or large?

i read your first post sould of done that....so are you running a Curtis action?

 

[NamibHunter]

Your data doesn't support your conclusion. You had as high as 20 fps ES within a single primer weight, and a max ES of 32 across all weights. The primer weight v muzzle velocity is a shotgun pattern, and by your own observation, the data do not support the linear fit. The variability in the data is dominated by factors other than primer weight. And, the ability to achieve single digit ES without primer sorting belays the contention that primer weight has an effect large nough to worry about.

Agree that a 0.23 R-square is a poor fit. Effect might not be real. Better data is needed (or a formal experimental design, and a batch of primers with more variability). I wish i had better data, but this is all i have. For now.

However, i do not have evidence to disprove that primers affect SD. Simply saying keep an open mind. For example: Run your own test. At least inspect the batch before use.

I think i have actually concluded the opposite: That primer weight is NOT a significant enough factor in MV variation (SD). The effect (if real) is tiny. At least in my current situation.

I still believe (perhaps in the absence of definitive proof) that there is a slight effect from primer weight difference (as most of that weight difference is in the priming compound, not the anvil or cup).

There is a good reason that reloading books recommend redoing load development if you change primer type, as a different make of primer can push you into overpressure. So the amount of priming compound and the chemical composition of the primer does (of course) affect speed. The chemical mechanism is there. The real question is if the factory is doing a good enough QC job so that you can ignore primer weight sorting. Or not.

Anyway. Take it for what it is worth.

 

[NamibHunter]

are you shooting a 6 or 65?..small firing pin or large?

i read your first post sould of done that....so are you running a Curtis action?

6.5 Creedmoor
Lapua and Alpha brass, both SRP primer pockets
Large firing pin
An early Curtis Axiom left handed action
26” barrel

Edit: Switch lug setup, but so far only one Spencer/MPA barrel in 6.5 CM

 

[NamibHunter]

ive shot more then i can remember 0 1 and 2FPS 5 shot groups...i shot a 65x47 and had a 10shot group that had a 1FPS ES...ive had only 1 40+ shot sample that was 15FPS every other large sample has been 18FPS + and most end up around 20-25ish...theres always the one fucker shot that screws it up.

Only twice did i get a 5 shot group that had an ES of 2. Usually 5-12 fps range for 5 shot groups. Which is too much!

Somewhere i have a gremlin that is messing up my SD. Maybe it is a donut? For large batches (30-50 rounds) i routinely get ES of 32 to 45 fps. Would love to half that number!

 

[47guy]

So large pin small primer is not the best combo you’d probably have better luck with a large primer or have your bolt bushed.

as far as SDs and ESs go there is a lot of things that can effect them...neck tension is a big one...an inconsistent firing pin fall will effect ESs..primers not seated the same...the list is long.

ive done all the brass prep weigh sorting trimming and tipping bullets you can think of and spent a LOT of time playing with all of it...when you stack all the tolerances it does make a difference but not enough for me and the type of shooting I do to warrant all the work.

I do not do any brass prep or sorting anymore...if I’m 25fps or under I’m good.

 

[47guy]

Also try some Peterson brass...I’ve replaced all my lapua with Peterson.

 

[NamibHunter]

Also try some Peterson brass...I’ve replaced all my lapua with Peterson.

Thank you 47 for the advice. Will try Peterson next time the budget allows for it.

As an aside, i have seen the biggest improvements in SD and group size in the past going from Hornady Match brass (rather poor) to Nosler Custom Competition brass. SD came down from the 12-15 fps range to around 10-13 fps. Then switched to Lapua SRP brass, and got SD below 10 for the first time. Now in the 7 to 11 fps range. My SD is not bad. But ES is way more than i want, usually because there are 1 or 2 outliers that mess up the numbers!

In my limited experience, Lapua and Alpha produce above average brass, but they are not perfect either. Measured neck thickness and often saw 0.001 to 0.0015 (1 to 1.5 thou) variations in neck thickness. Tried to cull out the worst cases, and that seemed to help. If Peterson beats them all, then that is where i need to go.

 

[47guy]

Thank you 47 for the advice. Will try Peterson next time the budget allows for it.

As an aside, i have seen the biggest improvements in SD and group size in the past going from Hornady Match brass (rather poor) to Nosler Custom Competition brass. SD came down from the 12-15 fps range to around 10-13 fps. Then switched to Lapua SRP brass, and got SD below 10 for the first time. Now in the 7 to 11 fps range. My SD is not bad. But ES is way more than i want, usually because there are 1 or 2 outliers that mess up the numbers!

In my limited experience, Lapua and Alpha produce above average brass, but they are not perfect either. Measured neck thickness and often saw 0.001 to 0.0015 (1 to 1.5 thou) variations in neck thickness. Tried to cull out the worst cases, and that seemed to help. If Peterson beats them all, then that is where i need to go.

try 50 and see what you think i bet youll be happy.

 

[strat81]

Brass was fully prepped and FL sized and shot well before. Alpha brass is thicker and has less internal capacity, but it has very consistent internal (water) volume, which ensures good reloading results.

Tell us about your brass prep.

Dies used, trim-to length, chamfer/deburr tool type, neck turning info, primer pocket uniforming, method of cleaning the brass, etc.

FWIW, the F-class guys I shoot with that win weight-sort their primers. CCI BR and FGMM are their preferred brands.

 

[calshipbuilder]

Here are my results from a few months back. These are CCI BR2s. 6xc w/115 DTACs. I now sort my larger rifle primers into .04gr.

 

[NamibHunter]

Here are my results from a few months back. These are CCI BR2s. 6xc w/115 DTACs. I now sort my larger rifle primers into .04gr.

View attachment 7177698

Thank you brother for posting hard data. Superb result!

Your data set is much better than mine, and frankly far more convincing. i can see why you sort primers. You observed a 50 fps delta attributable to primer weight changes (the amount the curve moved up over the full span of weight). That is a lot. [My result was less, but it is a different caliber and a different rifle, chamber etc., so not expecting them to be the same. Also, my data set was not great, and my delta speed nr could be higher (or lower) than i originally estimated.]

Would have been real nice if you had more data points at the bottom of the curve, where most of the curvature shows up. But i realize there are not enough examples to be found at the extremes of the Normal (or not) distribution. Most will land between +2 SD and - 2 SD.

Btw: Did a ladder test on my new tight chambered MPA rifle some 3 months ago, and the mean MV value for different loads follow a very similar curve. Huge speed losses once you go below a certain powder charge. Others have posted similar speed vs powder charge results for this particular MPA rifle. Given that, your choice of a nonlinear fit is justified. [I forgot to try that, but i will need more data points to do it justice. Maybe next week.]

What SD did you get before primer sorting, and what are you getting now?

Switched to GM205M primers as 47guy recommended for the load i shot yesterday, and downloaded 0.3 grains to avoid pressure signs. Used a sorted batch of Federal 205 primers (0.237 plus 0.238 grams, did not have enough to finish). Still a very narrow range. Sadly my SD went up from 8 to 11.3 fps.

But i think i know why: Speed dropped below my previously discovered top node. I guess there is more spark in a magnum primer. And the reduction in the load made it worse.

Also pretty sure that severe nonlinearity on the left side of your curve we both observed also kicked in (probably when the neck fails to seal off the chamber quickly enough, likely due to lack of pressure?). SD went up from 7-8 fps range to 11.3 fps. So not a happy result. Not blaming the Federal primers yet. The gun always show a higher SD when you are ‘out of the node’.... whatever primer you picked. Will have to repeat the experiment closeto max pressure.

Was hoping that the different choice of primer and weight sorring them would give me a single digit SD. Probably not a valid experiment if you drop outside of your rifle’s known. best node. Oh well. Onwards and upwards!

Once again, thanks for posting hard data!! This helps us all.

 

[calshipbuilder]

What SD did you get before primer sorting, and what are you getting now?

No problem, SD on that test was 13.2 with an ES of 65. This was pretty typical for me.

After weight sorting primers and brass, I routinely see an SD of 6 over 20 round strings in both 6xc and 7saum.

 

[NamibHunter]

No problem, SD on that test was 13.2 with an ES of 65. This was pretty typical for me.

After weight sorting primers and brass, I routinely see an SD of 6 over 20 round strings in both 6xc and 7saum.

That is a significant improvement (from 13 down to 6 fps). Well done!

Just curious: What is your new ES? [On long strings, like 50 shots, i often see ES=4*SD...]

Also what brass are you using? My biggest reduction in SD came from switching to better quality brass (more consistent internal volume). Yes i weight sort my brass.... but i have to admit that with most batches of Lapua, Nosler and Alpha, that is not strictly needed anymore.

 

[calshipbuilder]

[/QUOTE]

That is a significant improvement (from 13 down to 6 fps). Well done!

Just curious: What is your new ES? [On long strings, like 50 shots, i often see ES=4*SD...]

Also what brass are you using? My biggest reduction in SD came from switching to better quality brass (more consistent internal volume). Yes i weight sort my brass.... but i have to admit that with most batches of Lapua, Nosler and Alpha, that is not strictly needed anymore.

Thanks, its a journey, takes a while to sort out what actually matters. For instance, I have not been sorting small rifle primers. 3-4x the SD is what I usually see on ES

 

[NamibHunter]

Thanks, its a journey, takes a while to sort out what actually matters. For instance, I have not been sorting small rifle primers. 3-4x the SD is what I usually see on ES
[/QUOTE]

Curious what brass you are using...

Any special things you had to do to consistently get an SD below 10?

 

[NamibHunter]

Tell us about your brass prep.

Dies used, trim-to length, chamfer/deburr tool type, neck turning info, primer pocket uniforming, method of cleaning the brass, etc.

FWIW, the F-class guys I shoot with that win weight-sort their primers. CCI BR and FGMM are their preferred brands.

OK, rechecked EVERYTHING in detail, and found two major issues and a few minor ones:

For some reason, i had two pieces of Lapua brass in my Alpha batch, which will cause two shots with lower muzzle velocity. Alpha brass is thicker and has less internal volume. To correct for this unfortunate mishap, i removed the slowest two shots. SD came down from 11 to 9 fps. ES improved to 34 fps. Which i think is fairly decent.

Started up the LabRadar and wrote down the results of the last 13 batches (for 140 grain 6.5CM loads), from the most recent to the oldest results, with batch one corrected (two slowest numbers deleted).

Order is nr of shots/SD/ES:

34/9.1/34
38/8.5/32
36/6.4/26
43/9.1/33
24/9.8/34
24/6.4/23
18/7.4/26
47/7.5/29
23/9.1/35
18/10.8/39
23/11.7/43
22/11.9/47

Average SD is 8.8 fps, average ES is 32.8 fps. At least my results seem to be improving over the past few months.

The last 9 sets yield an average SD of 7.88 and an ES of 29.2 fps. [Yes, i corrected one set of results, but even if i did not, it would not have moved the mean value all that much.] I am satisfied with this result for now.

Found a minor donut on the false shoulder on the neck where the bushing stops sizing the neck. Took care of that with a Wilson neck reamer. Polished the inside of the cases with fine steel wool wound over a bronze brush in a power dril to remove the rough marks left by the reamer.

Will likely start with a fresh batch of Lapua or Peterson brass next week. New brass is the best cure for a donut.... If that moves my SD down, then it will be confirmation that a donut was the main problem. [The Lapua batch is 15x fired. Previous batch still had good primer pockets at 24x but necks were getting thin, so retired the batch out of an abundance of caution.]

Also got a little lazy and did not trim the cases every time, and some grew more than others. Took care of that too. I doubt that had a major effect.

So: I have decided that an SD below 10 is adequate for what i want to do at this point in my journey.

When i have time again, i will repeat the primer weight test, shooting mostly very light and very heavy primers, and some in the middle, and see if the SD can get above 0.5 by increasing sample size to 50.

In summary: As long as i can maintain SD between 6 and 9, i am content, and will resist going further down this rabbit hole. Not planning on sorting primers for now. If and when i get into ELR, then i will reconsider.

 

[calshipbuilder]

Curious what brass you are using...

Any special things you had to do to consistently get below an SD of 10?

For 6xc, Norma brass, sorted into 1 gr case weight. For neck tension I use a Sinclair carbide mandrel, and I jam the bullet well into the lands. Also, I switched off of H4350, varget, 4895 and H4831SC all gave better SDs.

 

[NamibHunter]

For 6xc, Norma brass, sorted into 1 gr case weight. For neck tension I use a Sinclair carbide mandrel, and I jam the bullet well into the lands. Also, I switched off of H4350, varget, 4895 and H4831SC all gave better SDs.

This is good info, thank you. I can see why a load with a jammed bullet will shoot at a more consistent speed, as neck tension is not the most dominant resistance force anymore to the bullet leaving the case. The engraving force as the bullet goes deeper into the lands will be the dominant “neck tension”. Of course you have to reduce powder charge to keep pressure from spiking, but that is well known.

Sadly, have tried a load with a jammed bullet in the MPA rifle, and for some strange reason the gun did not like it. Has worked well before in some of my other rifles.

I do have a few bottles of Varget and 4831SC, and will give that a try!

Thanks for the help sir.

 

[47guy]

So this was Sunday...I had to tap a new jug and lot # of bullets...i do not sort i do not weigh and i do not do any brass prep...i fire FL size with a .266 bushing i dry tumble trim and repeat...the 2952 and 2977 are the two that sent this to the SD of 5.

 

[NamibHunter]

So this was Sunday...I had to tap a new jug and lot # of bullets...i do not sort i do not weigh and i do not do any brass prep...i fire FL size with a .266 bushing i dry tumble trim and repeat...the 2952 and 2977 are the two that sent this to the SD of 5.

Very impressive 47! What kind of powder measure do you use?

 

[NamibHunter]

Update: After reaming the inside of the Lapua necks with the Wilson reamer, they were pretty rough inside. Scoured. Wound steel wool around a bronze wire brush, and then polished the inside of the necks until they were very smooth and shiny. Took a while, but it worked.

Used mica dry lube during seating: It is a very fine yellowish powder that is a good lubricant, but also an electrical insulator, so it is not going to participate in chemical corrosion reactions. Hoping to avoid bullet weld, which has occurred before. High humidity climate, Gulf Coast. [After tumbling the brass in a mix of corn cob and walnut with a small amount of mineral spirits and Nushine car wax, bullet weld has mostly gone away.]

Btw, last time, during seating step, the bullet would slide into the neck until the pressure ring hit the bottom of the sized neck area and then get stuck, taking a lot of force (>50 lbs) to finally seat in one loud thunk (arbor press). Believe it was forming a donut in that area. Now the bullet just glides in and it feels as smooth as butter. A real improvement. Will test the week-end. if this donut cleanup step does not solve the high ES problem, i plan to grab a new box of brass, and start over.

Thanks for all those that sent me PM messages with advice for how to overcome this. Have made good progress, and i hope/believe i am on the right track again!

 

[47guy]

Very impressive 47! What kind of powder measure do you use?

V3...if my charge is within 2 kernels + or - it goes in the case so i have at times a .04 or 4 kernel spread between cases which in theory is only 6-8FPS.

that said if you ran steel wool inside your necks its most likely going to cause more issues than you already have.

 

[DMP]

V3...if my charge is within 2 kernels + or - it goes in the case so i have at times a .04 or 4 kernel spread between cases which in theory is only 6-8FPS.

that said if you ran steel wool inside your necks its most likely going to cause more issues than you already have.

 

[NamibHunter]

V3...if my charge is within 2 kernels + or - it goes in the case so i have at times a .04 or 4 kernel spread between cases which in theory is only 6-8FPS.

that said if you ran steel wool inside your necks its most likely going to cause more issues than you already have.

Ok i am listening... always eager to learn. What is the effect of polishing the inside of the necks with steel wool?

If i have to start over with a fresh batch of brass, i am happy to do that too. [Just one last attempt to rescue the brass, if that is even possible. I kind of get a kick out of running the same batch of brass until i get close to 30 reloads.]

 

[calshipbuilder]

Ok i am listening... always eager to learn. What is the effect of polishing the inside of the necks with steel wool?

If i have to start over with a fresh batch of brass, i am happy to do that too. [Just one last attempt to rescue the brass, if that is even possible. I kind of get a kick out of running the same batch of brass until i get close to 30 reloads.]

I cleaned my cases too much once, and even with TBN coating, bullet seating pressure went nuts and SDs went from 8 to 24.

You can absolutely clean your cases too much. A thin layer of carbon and case lube - if consistent - is a good thing.

 

[47guy]

Ok i am listening... always eager to learn. What is the effect of polishing the inside of the necks with steel wool?

If i have to start over with a fresh batch of brass, i am happy to do that too. [Just one last attempt to rescue the brass, if that is even possible. I kind of get a kick out of running the same batch of brass until i get close to 30 reloads.]

take a piece of 0000 steel wool....i think thats the finest...or what ever your using...and rub it on the outside of a case.
steel wool leaves fine scratches in brass so if you used it inside the necks look at the outside you just steel wooled and as calshipbuilder said youve removed all or most of the carbon.

now im not sure if firing those cases a few times will smooth everything out or not but if it were me and i was having all these issues that brass would of been in the trash....in the big scheme of things brass is cheap when you factor in how many times you reload it.

 

[morganlamprecht]

did a comparison of primer weights quite a while back...all checked on a labradar

cci200s in 6creed (Hornady brass and 108 eld bullets both sorted), primer weights were the only variation...ran 10 round strings and saw each 0.1 gr in primer weight was worth ~12 fps avg...both strings had virtually no overlap iirc the low string was like 2980-2995 and the high string was from 2995-3010 fps...repeated this again and saw the same

tested it again with cci450s in a 6.5 creed (Lapua brass and 130 hybrids) and with cci200s in 308 (Lapua brass and 175 smk)...every time i found each 0.1 gr of primer weight to bump the average velocity ~10-15 fps with no real overlap...more primer weight was consistently higher

ive also taken the same 20 pcs of lapua brass and loaded them up without weight sorting any other component...i marked them 1-20 and i fired them in order checking speeds of each piece and found no real correlation to only the brass itself. Repeated this 3x and found some pieces of brass had a spread of <5 fps between all 3 firings, while the majority of pieces had spreads of 10-20 fps between 2 of the 3 shots. Lots of 2 out of the 3 firings being a spread of <5 fps, then 1 pushing the spread to 15 fps, for example. At the end, all 3 strings of 20 had overall similar numbers of 20-25 ES, and 5-8 SD, but the way those numbers were made up was random throughout the brass. Generally, in each string, the ES would be made up of 2-3 pcs that posted a 20-25 fps spread, and the other 17-18 pcs would have a spread of 10-15 fps.

all said, i havent and dont weight sort anything for the PRS/NRL matches i shoot...not that patient, i just buy good components and deal with it...i just checked it out of curiosity so id know if i ever needed to

 

[flyright]

Volume sorting brass and weight/ogive sorting bullets along with the FX for powder charging gave me some of the lowest SD/ES results I've ever gotten. SD of 3 or less and ES in single digits - SD of 1 and ES of 3 IIRC over 10 rounds - once. Accuracy improvement wasn't noticeable. No more of that for me. I wish I'd weighed primers while I was going through that phase. Good info.

 

[NamibHunter]

did a comparison of primer weights quite a while back...all checked on a labradar

cci200s in 6creed (Hornady brass and 108 eld bullets both sorted), primer weights were the only variation...ran 10 round strings and saw each 0.1 gr in primer weight was worth ~12 fps avg...both strings had virtually no overlap iirc the low string was like 2980-2995 and the high string was from 2995-3010 fps...repeated this again and saw the same

tested it again with cci450s in a 6.5 creed (Lapua brass and 130 hybrids) and with cci200s in 308 (Lapua brass and 175 smk)...every time i found each 0.1 gr of primer weight to bump the average velocity ~10-15 fps with no real overlap...more primer weight was consistently higher

ive also taken the same 20 pcs of lapua brass and loaded them up without weight sorting any other component...i marked them 1-20 and i fired them in order checking speeds of each piece and found no real correlation to only the brass itself. Repeated this 3x and found some pieces of brass had a spread of <5 fps between all 3 firings, while the majority of pieces had spreads of 10-20 fps between 2 of the 3 shots. Lots of 2 out of the 3 firings being a spread of <5 fps, then 1 pushing the spread to 15 fps, for example. At the end, all 3 strings of 20 had overall similar numbers of 20-25 ES, and 5-8 SD, but the way those numbers were made up was random throughout the brass. Generally, in each string, the ES would be made up of 2-3 pcs that posted a 20-25 fps spread, and the other 17-18 pcs would have a spread of 10-15 fps.

all said, i havent and dont weight sort anything for the PRS/NRL matches i shoot...not that patient, i just buy good components and deal with it...i just checked it out of curiosity so id know if i ever needed to

Interesting numbers. I got an 11.5 fps speed increase for a 0.09 grain primer weight increase. That works out to 13 fps per 0.1 grain. That is VERY close to your data (10-15 fps range). CalShipbuilder got about 20 fps towards the high end of his data range per 0.1 grain (higher at the low end). I think all three of these independently derived results triangulate quite well. Until there are more data sets listed, the 10-20 fps range per grain of primer weight increase seems to be the consensus estimate. [It is reasonable to expect that there will be differences between calibers and primer types.].

If you have additional data, please post it here! More is better.

My read of the situation is that if your rifle gets around 10 fps from primer weight differences, you will likely not benefit enough from sorting primers. If your rifle is closer to 20 or 25 fps,M per 0.1 grain, you probably should consider it. And check the quality of your primer batches, they are not all equally good. A standard scale with 0.1 gn resolution is good enough for this task. I would sample 20 random primers, and reject any batch with 0.3 grain weight differences (or larger).

Once again: Thanks guys for posting your data. This was very helpful!

 

[NamibHunter]

Volume sorting brass and weight/ogive sorting bullets along with the FX for powder charging gave me some of the lowest SD/ES results I've ever gotten. SD of 3 or less and ES in single digits - SD of 1 and ES of 3 IIRC over 10 rounds - once. Accuracy improvement wasn't noticeable. No more of that for me. I wish I'd weighed primers while I was going through that phase. Good info.

Very Impressive result.

I presume this was achieved in the center of the top node where speed goes flat for several 0.1 gn increments in powder, close to max pressure?

My experience is that SD more than doubles outside of the rifle’s best node. Does that also agree with your results during load development?

 

[NamibHunter]

take a piece of 0000 steel wool....i think thats the finest...or what ever your using...and rub it on the outside of a case.
steel wool leaves fine scratches in brass so if you used it inside the necks look at the outside you just steel wooled and as calshipbuilder said youve removed all or most of the carbon.

now im not sure if firing those cases a few times will smooth everything out or not but if it were me and i was having all these issues that brass would of been in the trash....in the big scheme of things brass is cheap when you factor in how many times you reload it.

Fair enough! Lapua brass (post donut removal/reduction) is now plinking ammo for friends and family members who occasionally go shoot with me.

Have now started reloading a fresh batch of Lapua brass, 1x fired so far and donut free. Will see how that goes.

Will avoid neck turning this time. Curious to see if that matters or not....

 

[47guy]

Fair enough! Lapua brass (post donut removal/reduction) is now plinking ammo for friends and family members who occasionally go shoot with me.

Have now started reloading a fresh batch of Lapua brass, 1x fired so far and donut free. Will see how that goes.

Will avoid neck turning this time. Curious to see if that matters or not....

brass prep weighing sorting is tolerance stacking so everything makes a tiny difference the thing you need to ask yourself is is all the extra work worth the time sorting..weighing and prepping?
for me NO i work 12+ hours a day and shooting is supposed to be fun....all that prep turns into a part time job and its no longer fun...im pretty sure the new brass will cure your issues.

 

[NamibHunter]

brass prep weighing sorting is tolerance stacking so everything makes a tiny difference the thing you need to ask yourself is is all the extra work worth the time sorting..weighing and prepping?
for me NO i work 12+ hours a day and shooting is supposed to be fun....all that prep turns into a part time job and its no longer fun...im pretty sure the new brass will cure your issues.

My sentiments exactly!

I am looking for the simplest and fastest possible reloading approach that gets my 100 yard groups below 0.5” and my SD below 9.9 fps. I have no intention of ever competing in BR. I prefer to hunt in the US, Canada and Africa, where head and neck shots impose a 1 MOA requirement. Yes i get a kick out of shooting the occasional 5 shot groups that measure 0.25”, and that gives me confidence in hunting situations, but if the aggregate/average is 0.45”, that is just fine by me. My MPA rifle is performing slightly better than that right now.

I have acquired quite a lot of good quality reloading equipment, every time hoping and expecting to notice an improvement in accuracy, and with very few exceptions, that just did NOT happen. Yes i understand about tolerance stacking, and that the one dominant factor that remains will hide these small improvements. Maybe my rifle’s firing pin fall is inconsistent (Tony Boyer mentions this in his book). How would i know? Does Sinclair sell a tool for measuring that too? ?

So what worked and what did not? (And yes some of this might be me not using the tools correctly...):

I saw improvements in groups at 600 yards, and reductions in SD as well as vertical dispersion ONLY from the following upgrades:

1) Dumping the original batch of unsorted Winchester (and Hornady) ‘match’ brass, all derived from factory match ammo, of different batches, and replacing it with one batch of Nosler custom competition brass. Nosler weight sorts and fully preps their brass before shipping. Weight range is about 1.0 grain, which is very narrow. That was the single biggest improvement i ever observed. Yes in my experience, Lapua and Alpha are very good too, but results on paper remained the same. [SRP brass just last so much longer, so that is a real benefit. Until they develop a donut at the false shoulder...]

2) A milligram electronic scale (initially a Gempro 250) was better than a mechanical RCBS scale. Gempro was accurate, but not robust (broke two in under two years), so replaced it with the AND FX120i. The FX would stabilize faster, which speeds up the reloading process, but the ammo is not noticeably more accurate on target paper.

3) Switching from Sierra 120 gn SMK to Berger 140 Hybrids in my 6.5 CM gave me noticeably less wind drift, as expected. Hornady ELD-M 140 and 147 gn projectiles gave almost the same performance.

4) Adding a good bubble level and paying attention to it helped a lot when shooting at longer distances. Obvious, but this is often overlooked by new shooters.

5) Finding a good wide node (speed range) where SD is minimized and speed is fairly flat for small changes in powder charge helped to keep SD close to 10. A good chrony is needed. MagnetoSpeed was adequate for this purpose. LabRadar is only slightly better. [At least they have dropped their price from the insane initial pricing of over $1000.]

6) Learning to use positive compensation, by reading targets (bullets marked with different color pens) and finding the speed range where bullet drop (vertical deflection is almost the same for different speed values) helped a lot at 600. No special equipment needed other than white target paper and different color permanent markers. Cheapest upgrade of them all.

7) Checking concentricity on a Sinclair or similar gauge. If you load carefully, using good brass, and your full length die is not mangling your brass, this is not needed. I have found that all loaded rounds with bullet runout less than 3 thou shoots well (or well enough by my standards). When i put aside the 2-3 messed up rounds with runout of 4-7 thou, and then check their accuracy and speed separately, i do find that they shoot worse. So my groups improved some by culling the really bad ones. Most batches have one or two. Brass that got dropped on the concrete floor at the range (bending the necks) tend to have very poor concentricity even after resizing (maybe due to brass springback?), and usually need to go into the warm-up or plinking pile. [Post firing, they are ok again.]

What did not seem to help, at least so far (or the beneficial effect was too small to stand out):

1) Annealing with a gas flame did not help group size or SD. Brass seems to shoot better 2 firings after the last annealing step... AMP machine made no discernible difference either. Over-hyped IMHO. [Yes, brass may perhaps last longer, but primer pockets opening up determine brass life for 6.5 CM, not neck splits.]

2) LabRadar is nice, and does not shift point of impact like MagnetoSpeed, so drop calcs are more accurate. But that does not improve groups on paper. Accurate yes. Overpriced, yep!

3) Autotrickler is very nice and speeds up the reloading process. But no more accurate than a human paying attention and using a $20 manually operated powder trickler. Good productivity, but expensive.

4) Force measurement arbor press (for use with Wilson hand dies). It does tell me something about donuts, neck tension, brass springback, and such. But you can learn to pick that up from a standard press too. I have NOT found any correlation between peak seating force and group size, or SD. R-square was below 5%. Theoretically, there must be a relationship, but i have fired hundreds of rounds where i knew the peak seating force and recorded the speed, plotted them, and there was NO relationship! This was a real surprise. Maybe the gas pressure (force) needed to move the bullet out by the tiny amount of bullet jump you run is very different from the PEAK seating force? Peak force typically occurs when the pressure ring on the bullet goes past the false shoulder caused by the sizing bushing, and i seat them more than the bullet jump amount below the false shoulder (but still above neck shoulder junction), to feed from the mag. If the inside of the neck is not perfectly round, maybe the bullet is resizing the neck and the donut on the way in, creating a larger peak force, but when the bullet is pushed out of the case (from a neck that is now more round than before), the required force is a lot less... Who knows!

5) Neck turning has not helped group size. Yes, concentricity is a little better, and neck tension is a little more consistent if you use bushing dies, but group size and SD stayed the same.

 

[47guy]

My sentiments exactly. I am looking for the simplest and fastest reloading approach that get my 100 yard groups below 0.5” and my SD below 9.9 fps. I have no intention of ever competing in BR. I prefer to hunt in the US, Canada and Africa, where a head and neck shots impose a 1 MOA requirement. Yes i get a kick out of shooting the occasional 5 shot groups that measure 0.25”, but of the aggregate/average is 0.45”, that is just fine by me.

I have acquired quote a lot of good quality equipment, every time expecting to notice an improvement in accuracy, and with very few exceptions, that just did NOT happen. So what worked and what did not? (And yes some of this might be me not using the tool correctly...)

I saw improvements in groups at 600 yards, and reductions in SD as well as vertical dispersion ONLY from the following upgrades:

1) Dumping the original batch of unsorted Winchester ‘match’ brass (derived from factory match ammo) and replacing it with Nosler custom competition brass. Nosler weight sorts and fully preps their brass before shipping. Weight range is about 1.0 grain, which is a very narrow range. That was the single biggest improvement i ever experienced. Yes in my experience, Lapua and Alpha are very good too, but resultsbremained rhe same. SRP brass just last longer, so that is real a benefit. Until they develop a donut at the false shoulder.

2) Using a milligram electronic scale (initially a Gempro 250) was better than a mechanical RCBS scale. Accurate, but not robust, so replaced it with the FX120i. The FX would stabilize faster, which speeds up the process, but not noticeably more accurate on target paper.

3) Switching from Sierra 120 gn SMK to Berger 140 Hybrid gave me less wind drift. As expected. Hornady ELD-M 140 and 147 gn projectiles gave almost the same performance.

my suggestion take it for what it’s worth...

ditch the bushing die and buy a FL none bushing die...buy a set of expander balls to set neck tension to .002.

when sizing use hornady one shot as an inside neck lube and don’t do any case prep...buy good brass and shoot it.