Lapua 223 weight vs. volume & field testing of 21st Century Primer Pocket Plug

[jlow]

Wanted to see if my now 1x fired Lapua 223 brass weight correlates to volume. I purchased 400 cases from the same batch and weight sorted them. The cases from this study are from the lighter half of the batch which range from 94.3 to 95.0 grains. The heavier half range from 95.1 to 96.4 grains and were not part of this study.

Cases were deprimed, cleaned with SS media, FLR, shoulders bumped back 0.003”, neck sized with a LCD, and lube removed. No trimming was necessary. The cases were weight sorted and binned in 0.1 grain increments and one case was taken from each bin for a total of 17 cases.

For volume measurement, cases were first weight empty, plugged with the 21st Century tool, the Gempro 250 was tarred with the case/plug combo and then partially filled with rubbing alcohol. The cases were then filled until the meniscus was flat with rubbing alcohol using a syringe/needle and the added weight noted.

At the start of the study, a single case (94.34 grain) was primed with a Wolf SRM primer and its volume determined as described above – three volume measurements were done – the liquid weights were 26.78/26.74/26.78 grains. The case was then deprimed and residue alcohol blown out with compress air. The weight of the case was then check to make sure that it had not changed (i.e. by residue alcohol). The case was then plugged with the 21st Century primer tool, the case was placed on the balanced and tared. Case volume was again measured using the above method 3 times. Liquid weights were 26.80/26.78/26.80 grains.

So a number of conclusions. One is the 21st Century tool was an excellent replacement for the primer giving statistically equivalent case volume weights. I had slight problem with this tool at first with unfired Lapua brass as its primer pocket was a bit tight but this was not a problem with fired cases. My only regret is not buying 2 instead of one, that way I could transfer the alcohol from one case directly to another without pouring it back into the bottle.

The attach graph showed that despite the slight difference in the weight of the cases used in this study i.e. 0.7 grains, one can clearly see the correlation between case weight and the weight of the liquid it held and therefore case volume. Correlation coefficient was 0.57 (0 means no correlation and 1 is perfect correlation).

 

[dmoran]

All with in .4-tenths... not bad !.!.! .... (but is more typical with small cases like the 223).
The heaviest did not hold the least, and the lightest did not hold the most, which tells the story well enough.
A .57 ratio is pretty darn good compared to most all I have checked over the years (usually bigger capacity cases).

Thanks for taking the time and for sharing !.!.!
Donovan

 

[jlow]

Glad to share since I have received so much from this board.

Yes, I had good luck using this same method with LC09 brass and so was wondering how the Lapua would correlate. You are absolutely right about heavier cases weight did not correlate with volume, that is what I found too, always wonder about that and may do more with the 21st Century large primer plug and my new Lapua 308 cases to see what I can come up with...

 

[dmoran]

Be interesting to see a larger sample (say 100 out of the 400 = 25%) of those cases to see how it unfolds, since 15 is a pretty small sample out of 400 total cases (less then 4%).

Again.... Thanks for taking the time and for sharing !.!.!
Donovan

 

[stool]

nice INFORMATION, but not DATA.
as was pointed out too small of a sample.
i did one lot of about 500 win 223 cases. got 30 that weighed the same...and bingo...the volume on all 30 were the same.

 

[6BRinNZ]

Jlow - do you think you will take those 15 cases and shoot them over the chrony?

 

[mysticplayer]

Nice work and illustrates why I quit weighing cases a long time ago.

if the case volume is within your accepted ranges, the mass of the case is irrelevant.

I am sure if you sampled more, the population would simply reflect what you have already shown.

There is no correlation between case weight and case volume when measuring at these levels.

I also stopped using fluid a long time ago. Instead a very fine ball powder like Win 680 is used to fill the case and can be easily and quickly dumped into another case. Tap the case so the powder can settle and it is extremely high load density.

When you dump into the next case, it should actually be more then the case can hold until you tap the case. That tells me there is more then enough consistency in the result to matter.

I will cull cases that show a variation in powder volume of 1/16" above or below the case top for a 223. The number of cull cases from any particular lot of win brass is very small.

So I will grab 20 to 30 cases out of batch of same lot brass, do this test and if they all measure tight, assume the rest is good and go shoot them.

Jerry

 

[stool]

big mistake...unless 2" groups at 100 are ok with you..

from my first post...500 pc single batch of win 223 brass......
weight sorted the entire batch.
the results were a bell curve......
the problem was the ends of the curve were very long....i do not have my data right now but
this was a big jump from the middle to either end.
you pick up 20 pcs from the middle and one from either end and you have a flyer in your data.
i got 350 pcs in 7 50 pcs lots plus the 30 pc lot...that means 100 plus pcs that were outside my .5 spread per lot....some on each end..
i think win brass is a good deal, but if you do not weight sort it, you are asking for flyers.

Nice work and illustrates why I quit weighing cases a long time ago.

if the case volume is within your accepted ranges, the mass of the case is irrelevant.

I am sure if you sampled more, the population would simply reflect what you have already shown.

There is no correlation between case weight and case volume when measuring at these levels.

I also stopped using fluid a long time ago. Instead a very fine ball powder like Win 680 is used to fill the case and can be easily and quickly dumped into another case. Tap the case so the powder can settle and it is extremely high load density.

When you dump into the next case, it should actually be more then the case can hold until you tap the case. That tells me there is more then enough consistency in the result to matter.

I will cull cases that show a variation in powder volume of 1/16" above or below the case top for a 223. The number of cull cases from any particular lot of win brass is very small.

So I will grab 20 to 30 cases out of batch of same lot brass, do this test and if they all measure tight, assume the rest is good and go shoot them.

Jerry

 

[dmoran]

i did one lot of about 500 win 223 cases. got 30 that weighed the same...and bingo...the volume on all 30 were the same.

I've been weighing cases and measuring volume's for 15 years or so, and only one time of all the different brands and calibers did I see a direct correlation like you claim happens. It was with one box of Lapua 220-Russian (used to form 6PPC) that held .2-tenths across a lot of 98.
Except for that one lot being very close, not once have I seen a direct linear correlation, and more times then not, they are far from any correlation between weight and volume.

I have had cases that weighed as much as 4-grains difference but had near same volume capacities, and others that weigh the same that have had +7-tenths variance in volume (a lot of 243 Winchester's).

Cut 10 case heads off in lathe to equal length, weigh the heads and you will see where most the weight variations come from in brass. Mill into a couple length ways and see how much thickness variation there can be from side to side, particularly nearer the webbing walls and again in the shoulder wall.

Like I have said before, I wish case weights correlated with capacity, would make my life much simpler... but they don't.
Donovan

 

[jlow]

Sorry for the slow response, it’s that time for Christmas parties….

Actually I have done more but those were done when the cases were new unfired and had primers included in the weight so I could not bundle the data together. The reason there are more is because I have been weighting and doing volume determinations as I shoot the brass in the last few outings. So since you guys are interested I will post that data here.

So there are a total of 52 additional cases and as already mentioned, these are new unfired Lapua brass with a spent primer put in and the weight here reflects the weight of the case + spent primer (OP study had case only weight). The other thing that is different here is I have converted the weight of the denature alcohol to volume in mL. As can be seen, we see the same relationship between weight and volume with slightly worse correlation. The reason for this is most likely because this was done at the end of my run with the batch of cases and so the weight variation was low (0.40 grains vs. 0.7 grain in the study in the OP). The lower the weight variation, the more noise effect will affect the correlation. Variation in primer weight may have a effect but my guess is it was insignificant.

I have also included an additional study I did with LC09 cases back in 2012. Here the case weight variation was greater – 1.57 grains. The number of cases measured was 20 but the correlation coefficient between case weight (without primers) and weight of denature alcohol was 0.72 which is very significant.

I know there are strong feelings that are “stirred up” whenever something like this shows up. I share this data only to add to the information pool. This data does not prove in any way that the same weight volume relationship exist for all caliber cases but only for the specific caliber and brand of cases that I have tested, and only within the weight range specified. As a matter of fact, using the same technique I have been unable to show the same relationship with Win308 brass.

I realize that people still may not be convinced – that to me is OK. I am not here to convince just to share. The only thing I would ask is for people to keep an open mind and if you have data that conflicts with this, that is fine, show us the data so that we can discuss and learn.

6BRinNZ – as of now, I have no plans to do this since I live in MI and temps here right now is in the teens… That is not to say that the study could not be done in the future. What I can say is if you use QuickLoad, you can do some hypothetical studies by putting in different case volume which will show you how it may affects MV. Of course that is not real data.

 

[stool]

i agree. do what you want and what makes you feel good...
but i have done enough that i have documentation of to satisfy me, that i will continue to weight sort.......
my rws brass for my 300 win mag is plus or minus 0.05....it took just over 1000 pcs to get two 100 pc lots.

 

[CatShooter]

There is a last thing....

For any experiment to be valid, it must be repeatable, and the methodology must be repeatable.

So, what is the variation if you do one case five times - slowly dropping the powder down a ~10"" drop tube (even fine ball powder can have variations in packing density, and needs to be dropped through a tube).

Then test your 10 cases (or 20 or whatever sample size you want), two or three times.

Then you have really definitive information.

As it is now, you don't know if the results are due to accurate variations in volume, or inaccurate variations in methodology.

I tend to think the latter.

 

[jlow]

CatShooter – your point about experiment to be valid that it must be repeatable is a good one. I myself having a Ph.D. in a scientific area and having worked for 30 years of research of course would heartily agree with you.

The denature alcohol method is absolutely repeatable and one of the first thing I did when I was developing this method before I started to use it is to validate the method in terms of how repeatable it was. If you look at the OP, you will see that I did that before using the 21st Century primer pocket plug for this very reason. Not only did I see if I could do a reproducible measure but I check to see if the value I got with the plug was equivalent to that from a primer. As a rule, I make 3 measurements per sample.

Sure one can do the same experiment with the same brass 2-3 times (apart from an N=3 of measurements which I already did) but the fact is if you truely understand the principle of scientific proof, you will see that it is even more convincing if one does three experiments from three different lots of cases and different manufacturer and show the same results – after all, the one lot I did in the OP could be a fluke… But the same results from three different lots and even manufacturer would be much less likely to be a fluke.

Like I said, if you don’t believe the results, it’s OK by me as my days of reporting to thesis or company research committee has luckily long passed… but at least to a scientist who works with scientific method (which is what I think you are talking about), you would be a whole lot more convincing to the reader if you show your own evidence that is also validated that shows a different result. Just saying no I don’t believe or my evidence that I don’t’ show is different has little or no bearing on the discussion.

 

[Richard Whitcomb]

Wanted to see if my now 1x fired Lapua 223 brass weight correlates to volume. I purchased 400 cases from the same batch and weight sorted them. The cases from this study are from the lighter half of the batch which range from 94.3 to 95.0 grains. The heavier half range from 95.1 to 96.4 grains and were not part of this study.

Cases were deprimed, cleaned with SS media, FLR, shoulders bumped back 0.003”, neck sized with a LCD, and lube removed. No trimming was necessary. The cases were weight sorted and binned in 0.1 grain increments and one case was taken from each bin for a total of 17 cases.

For volume measurement, cases were first weight empty, plugged with the 21st Century tool, the Gempro 250 was tarred with the case/plug combo and then partially filled with rubbing alcohol. The cases were then filled until the meniscus was flat with rubbing alcohol using a syringe/needle and the added weight noted.

At the start of the study, a single case (94.34 grain) was primed with a Wolf SRM primer and its volume determined as described above – three volume measurements were done – the liquid weights were 26.78/26.74/26.78 grains. The case was then deprimed and residue alcohol blown out with compress air. The weight of the case was then check to make sure that it had not changed (i.e. by residue alcohol). The case was then plugged with the 21st Century primer tool, the case was placed on the balanced and tared. Case volume was again measured using the above method 3 times. Liquid weights were 26.80/26.78/26.80 grains.

So a number of conclusions. One is the 21st Century tool was an excellent replacement for the primer giving statistically equivalent case volume weights. I had slight problem with this tool at first with unfired Lapua brass as its primer pocket was a bit tight but this was not a problem with fired cases. My only regret is not buying 2 instead of one, that way I could transfer the alcohol from one case directly to another without pouring it back into the bottle.

The attach graph showed that despite the slight difference in the weight of the cases used in this study i.e. 0.7 grains, one can clearly see the correlation between case weight and the weight of the liquid it held and therefore case volume. Correlation coefficient was 0.57 (0 means no correlation and 1 is perfect correlation).

CatShooter – your point about experiment to be valid that it must be repeatable is a good one. I myself having a Ph.D. in a scientific area and having worked for 30 years of research of course would heartily agree with you.

The denature alcohol method is absolutely repeatable and one of the first thing I did when I was developing this method before I started to use it is to validate the method in terms of how repeatable it was. If you look at the OP, you will see that I did that before using the 21st Century primer pocket plug for this very reason. Not only did I see if I could do a reproducible measure but I check to see if the value I got with the plug was equivalent to that from a primer. As a rule, I make 3 measurements per sample.

Sure one can do the same experiment with the same brass 2-3 times (apart from an N=3 of measurements which I already did) but the fact is if you truely understand the principle of scientific proof, you will see that it is even more convincing if one does three experiments from three different lots of cases and different manufacturer and show the same results – after all, the one lot I did in the OP could be a fluke… But the same results from three different lots and even manufacturer would be much less likely to be a fluke.

Like I said, if you don’t believe the results, it’s OK by me as my days of reporting to thesis or company research committee has luckily long passed… but at least to a scientist who works with scientific method (which is what I think you are talking about), you would be a whole lot more convincing to the reader if you show your own evidence that is also validated that shows a different result. Just saying no I don’t believe or my evidence that I don’t’ show is different has little or no bearing on the discussion.

CatShooter – your point about experiment to be valid that it must be repeatable is a good one. I myself having a Ph.D. in a scientific area and having worked for 30 years of research of course would heartily agree with you.

The denature alcohol method is absolutely repeatable and one of the first thing I did when I was developing this method before I started to use it is to validate the method in terms of how repeatable it was. If you look at the OP, you will see that I did that before using the 21st Century primer pocket plug for this very reason. Not only did I see if I could do a reproducible measure but I check to see if the value I got with the plug was equivalent to that from a primer. As a rule, I make 3 measurements per sample.

Sure one can do the same experiment with the same brass 2-3 times (apart from an N=3 of measurements which I already did) but the fact is if you truely understand the principle of scientific proof, you will see that it is even more convincing if one does three experiments from three different lots of cases and different manufacturer and show the same results – after all, the one lot I did in the OP could be a fluke… But the same results from three different lots and even manufacturer would be much less likely to be a fluke.

Like I said, if you don’t believe the results, it’s OK by me as my days of reporting to thesis or company research committee has luckily long passed… but at least to a scientist who works with scientific method (which is what I think you are talking about), you would be a whole lot more convincing to the reader if you show your own evidence that is also validated that shows a different result. Just saying no I don’t believe or my evidence that I don’t’ show is different has little or no bearing on the discussion.

Hi,
I have been trying to find out where to buy the 21 st Century primer plug .PLEASE LET ME KNOW WHERE TO BUY ONE. THANK YOU!

 

[Jdne5b]

Hi,
I have been trying to find out where to buy the 21 st Century primer plug .PLEASE LET ME KNOW WHERE TO BUY ONE. THANK YOU!

http://www.xxicsi.com/primer-pocket-plugs.html