reconsidering measuring case weight

[jimcasey01]

Do you want in spreadsheet form or just results. Basically dry case weight has very little bearing on case capacity until case weight variation is at extremes. Then there is a strong correlation. Also, we are all working to varying minimum standards. What is minor to one person is major to another.

I originally misread what you were asking. I can post results by this evening, I have honey-do's til this afternoon.

 

[jlow]

The process is not messy and only “chock-full of potential errors” only if you don’t know what you are doing. If you want to know how to do it right – read on.

Jim Casey suggestion of using the 21st Century primer plug is a good one, they work. Other suggestions I can give are:

1. Don’t use water but rubbing alcohol as alcohol has a lower surface tension and will form less of a meniscus, it also has a lower tendency to form bubbles inside the case.

2. Fill the case first almost to the top with rubbing alcohol a hair dyer’s bottle which has a sharp tip. Fill it the rest of the way with a 27 gauge Tuberculin syringe which is available in pharmacies.

3. When you fill the case with the syringe, wear a head magnifier and place the case between you and a small table lamp – I use one with an array of LED.

4. As you fill the case, position your head so that the reflection of the lights’s LEDs is visible in the surface of the rubbing alcohol at the mouth of the case.

5. The image of the LEDs will start small and will enlarge as you fill the case. This is cause by the concave nature of the meniscus when the case is not full. As the meniscus gets less concave, it will magnify the reflection of the LED which will make it bigger. It will enlarge to the point where it is so big that it will disappear when the meniscus is flat. If you over fill the case, the meniscus will now become convex and at that point the LED image will again start to appear and getting smaller when the meniscus becomes more convex.

6. If you spill down the side of the case or on the balance, wipe it up as it will of course change your apparent liquid weight.

7. I would suggest you repeat the process 3x for each case and use the average value. This is simple to do – you use the syringe to aspirate a small amount off the surface and repeat from the above step #4.

The technique is only as good as the quality of your skill and that usually need practice. Don’t do any real volume determination until you can measure one case over and over again and get a reproducible values. It is never going to be perfect but for example, in my hands, a Lapua 308 case has around a volume of 48 grains of rubbing alcohol with a variation between the lightest and heaviest of around 0.5 grains. If your error measuring the same case comes close to that, it should be obvious that you are NOT going to get anywhere....

My own results are also not perfect but variation of the three measurements for each of the 40 cases range between 0.00 to 0.08 grains with an average error of 0.04 grains. You generally cannot get perfect results as the syringe dispense fluid in drops and each small drop can weigh as much as 0.04 grain, so an average error of 0.04 grains means you are plus or minus one drop which is just about as good as you can do.

This is my data from the last Lapua 308 measurement compare case weight to volume. Correlation coefficient of 0.8 means it is good.

 

[jimcasey01]

Jlow, I am in no way a statistician, and am in no way disputing your info. I tried to post spreadsheet and had problems with it being legible. I will try again tonight. It very well be that my results are similar to yours, and I may be too critical on the term "correlation".

 

[jlow]

No sweat, I too am not a statistician (God forbid.. ;D). If you are having problem posting spreadsheet, just try to do a “Print screen” and post as a JPEG.

 

[BCoates]

I was looking at the graph above that jlow supplied. Looking at the results, if I sort my 308 Lapua brass into 1 gr batches each batch of cases should have about 0.1 - 0.12 gr (alcohol) capacity variance. This means there is about 0.12 - 0.15 gr difference in water volume capacity. I don't know how much this level of capacity variation with change velocity, but from my testing with IMR4064, a 0.1 gr difference in charge weight in a 308 Win = 8-10 fps. If I could get my ES down to that level I would be extremely happy.

 

[savagedasher]

Jim using you figures of H20 capacity .
The high being 30.99 with loading 23gr of benchmark and 64gr Berger 2.60 oal The number from QL are
30.99 H20 90.9 fill 45360 psi 3014 fps
30.2 H20 93.5 fill 47852 psi 3044 fps
The reason for weighing H20 capacity is to narrow the difference no matter the total case weight.
You have .04 fill difference 2492 psi difference 30'fps difference.
To me 2492 psi and 30fps difference is not what I want. Shooting at 1000yd.
By doing nothing but H20 Capacity you can lower Es to 5' not the 30 it shows here.
By sorting my cases in H20 capacity I have ben able to keep my Es at 3
From building race motors the cc of a chamber is no different then case capacity
Great job Larry

 

[jimcasey01]

Larry,
I did not know that the info I posted was up long enough for anyone to see, but you have my figures correct. It appeared jumbled on my copy of the post. I will try again in a few minutes to break down and and post again.

 

[jimcasey01]

Lapua Brass .223 Remington Case dry weight difference heaviest to lightest is 2.38 grains.
Necks turned to .0127 Variation is .0124-.0128 Approximately 85-95% fall within .0127 +/-.0001
Cases are trimmed to 1.7502 +/-.0001 for 80-90% of cases, max of +/-.0002
Sample size is 129 cases All of the case weights include the primer plug
Case capacity 30.2-30.99 grains of water
Of this group 2 fell outside of the stated capacity, 1 under, 1 over weight.

H2O Total 127 Average Weights amount % 30.67 30.2 2 1.57% 30.25 5 3.94% Median 30.3 7 5.51% 30.71 30.35 2 1.57% 30.4 4 3.15% Max 30.45 2 1.57% 30.96 30.5 5 3.94% 30.55 5 3.94% Min 30.6 9 7.09% 30.23 30.65 16 12.60% 30.7 26 20.47% Variation 30.75 19 14.96% 0.73 30.8 10 7.87% 30.85 9 7.09% 30.9 6 4.72% 30.95 3 2.36%

Another post to follow with actual weights if this works.

 

[jimcasey01]

Still having a problem but should be readable. Column 1= case number, column2=my sort weight column 3=dry weight case grams(includes weight of primer plug) column 4= case only dry weight in grains column 5=wet weight(with plug) column 6=difference (water weight) column 7= column #6 in grains. All other measurements are in grams except #4, which is grains.
You can compare the dry weights column 4 to case capacity in columns 7

# Sort Dry wt wt gr Wet wt H2O Cap H2O cap gr 011 23 23.653 95.65 25.612 1.959 30.23 098 23 23.661 95.78 25.62 1.959 30.23 030 26 23.647 95.56 25.608 1.961 30.26 116 29 23.62 95.14 25.583 1.963 30.29 128 29 23.655 95.68 25.618 1.963 30.29 005 29 23.656 95.70 25.619 1.963 30.29 009 29 23.646 95.54 25.609 1.963 30.29 050 31 23.647 95.56 25.611 1.964 30.31 056 32 23.658 95.73 25.623 1.965 30.32 066 32 23.654 95.67 25.619 1.965 30.32 087 32 23.653 95.65 25.618 1.965 30.32 111 32 23.617 95.10 25.582 1.965 30.32 123 34 23.629 95.28 25.595 1.966 30.34 008 34 23.641 95.47 25.607 1.966 30.34 109 37 23.575 94.45 25.543 1.968 30.37 081 39 23.582 94.56 25.551 1.969 30.39 068 40 23.605 94.91 25.575 1.970 30.40 072 40 23.574 94.43 25.544 1.970 30.40 018 43 23.595 94.76 25.567 1.972 30.43 129 43 23.552 94.09 25.524 1.972 30.43 041 46 23.59 94.68 25.564 1.974 30.46 112 46 23.591 94.69 25.565 1.974 30.46 003 51 23.646 95.54 25.623 1.977 30.51 119 51 23.632 95.33 25.609 1.977 30.51 002 53 23.643 95.50 25.621 1.978 30.53 054 53 23.607 94.94 25.585 1.978 30.53 075 54 23.586 94.62 25.565 1.979 30.54 006 56 23.649 95.59 25.629 1.980 30.56 076 56 23.643 95.50 25.623 1.980 30.56 077 57 23.687 96.18 25.668 1.981 30.57 048 57 23.581 94.54 25.562 1.981 30.57 062 59 23.599 94.82 25.581 1.982 30.59 092 60 23.63 95.30 25.613 1.983 30.60 059 62 23.634 95.36 25.618 1.984 30.62 084 62 23.632 95.33 25.616 1.984 30.62 007 63 23.643 95.50 25.628 1.985 30.63 017 63 23.646 95.54 25.631 1.985 30.63 070 63 23.628 95.27 25.613 1.985 30.63 085 63 23.625 95.22 25.610 1.985 30.63 106 63 23.613 95.03 25.598 1.985 30.63 127 63 23.62 95.14 25.605 1.985 30.63 073 65 23.609 94.97 25.595 1.986 30.65 024 65 23.611 95.00 25.597 1.986 30.65 058 65 23.636 95.39 25.622 1.986 30.65 061 65 23.647 95.56 25.633 1.986 30.65 064 65 23.646 95.54 25.632 1.986 30.65 069 66 23.638 95.42 25.625 1.987 30.66 110 66 23.593 94.73 25.58 1.987 30.66 096 66 23.615 95.07 25.602 1.987 30.66 020 68 23.592 94.71 25.58 1.988 30.68 053 68 23.613 95.03 25.601 1.988 30.68 055 68 23.646 95.54 25.634 1.988 30.68 091 68 23.63 95.30 25.618 1.988 30.68 090 69 23.617 95.10 25.606 1.989 30.69 113 69 23.596 94.77 25.585 1.989 30.69 114 69 23.613 95.03 25.602 1.989 30.69 121 69 23.642 95.48 25.631 1.989 30.69 032 71 23.655 95.68 25.645 1.990 30.71 102 71 23.625 95.22 25.615 1.990 30.71 117 71 23.617 95.10 25.607 1.990 30.71 122 71 23.588 94.65 25.578 1.909 30.71 004 71 23.644 95.51 25.634 1.990 30.71 027 71 23.598 94.80 25.588 1.990 30.71 034 71 23.618 95.11 25.608 1.990 30.71 049 71 23.63 95.30 25.62 1.99 30.71 079 71 23.616 95.08 25.606 1.990 30.71 086 71 23.578 94.49 25.568 1.990 30.71 095 71 23.589 94.66 25.579 1.990 30.71 015 73 23.602 94.86 25.593 1.991 30.73 022 73 23.599 94.82 25.59 1.991 30.73 026 73 23.616 95.08 25.607 1.991 30.73 074 73 23.605 94.91 25.596 1.991 30.73 083 73 23.584 94.59 25.575 1.991 30.73 094 73 23.618 95.11 25.609 1.991 30.73 107 73 23.580 94.53 25.571 1.991 30.73 100 74 23.594 94.74 25.586 1.992 30.74 103 74 23.588 94.65 25.580 1.992 30.74 013 74 23.618 95.11 25.610 1.992 30.74 014 74 23.642 95.48 25.634 1.992 30.74 029 74 23.657 95.71 25.649 1.992 30.74 080 74 23.593 94.73 25.585 1.992 30.74 104 74 23.617 95.10 25.609 1.992 30.74 120 74 23.592 94.71 25.584 1.992 30.74 025 76 23.559 94.20 25.552 1.993 30.76 037 76 23.629 95.28 25.622 1.993 30.76 040 76 23.620 95.14 25.613 1.993 30.76 082 76 23.640 95.45 25.633 1.993 30.76 115 76 23.599 94.82 25.592 1.993 30.76 052 76 23.592 94.71 25.585 1.993 30.76 097 76 23.583 94.57 25.576 1.993 30.76 105 76 23.589 94.66 25.582 1.993 30.76 001 77 23.637 95.40 25.631 1.994 30.77 099 77 23.584 94.59 25.578 1.994 30.77 101 77 23.606 94.93 25.600 1.994 30.77 125 77 23.595 94.76 25.589 1.994 30.77 044 79 23.591 94.69 25.586 1.995 30.79 063 79 23.594 94.74 25.589 1.995 30.79 010 79 23.615 95.07 25.610 1.995 30.79 021 79 23.611 95.00 25.606 1.995 30.79 060 79 23.622 95.17 25.617 1.995 30.79 078 79 23.58 94.53 25.575 1.995 30.79 108 79 23.587 94.63 25.582 1.995 30.79 012 80 23.593 94.73 25.589 1.996 30.80 016 80 23.588 94.65 25.584 1.996 30.80 071 80 23.561 94.23 25.557 1.996 30.80 035 80 23.592 94.71 25.588 1.996 30.80 047 80 23.612 95.02 25.608 1.996 30.80 028 82 23.545 93.98 25.542 1.997 30.82 045 82 23.578 94.49 25.575 1.997 30.82 067 82 23.632 95.33 25.629 1.997 30.82 118 82 23.615 95.07 25.612 1.997 30.82 126 83 23.616 95.08 25.614 1.998 30.83 019 85 23.563 94.26 25.562 1.999 30.85 031 85 23.612 95.02 25.611 1.999 30.85 124 86 23.533 93.80 25.533 2.000 30.86 088 88 23.545 93.98 25.546 2.001 30.88 093 88 23.533 93.80 25.534 2.001 30.88 065 88 23.578 94.49 25.579 2.001 30.88 038 90 23.565 94.29 25.567 2.002 30.90 039 90 23.597 94.79 25.599 2.002 30.90 043 91 23.592 94.71 25.595 2.003 30.91 033 93 23.575 94.45 25.579 2.004 30.93 042 93 23.619 95.13 25.623 2.004 30.93 057 94 23.598 94.80 25.603 2.005 30.94 023 96 23.568 94.34 25.574 2.006 30.96 051 96 23.595 94.76 25.601 2.006 30.96 089 96 23.592 94.71 25.598 2.006 30.96 036 23.62 95.14 25.563 1.943 046 23.651 95.62 25.663 2.012

 

[jimcasey01]

Sorry for using 2 weight systems, easier for me to work in grams. When calculating grams to grains I used 15.4323584 grains to = 1 gram, which is 7 decimal places, then rounded results to 2 decimal places. The 15.4323584 number will allow you to get an idea of dry weight differences. I know its a PIA but you will have to do the math here.

I added a column, #4 which is the case dry weight in grains.

 

[jimcasey01]

If any of you wish to use the term anal-retentive to describe me, I can not argue with you on that statement.

 

[savagedasher]

If any of you wish to use the term anal-retentive to describe me, I can not argue with you on that statement.

Good job Jim
It would be nice to have the internal volume listed. by hi to low or low to hi.
Larry

 

[jimcasey01]

If any of you wish to use the term anal-retentive to describe me, I can not argue with you on that statement.

Good job Jim
It would be nice to have the internal volume listed. by hi to low or low to hi.
Larry

Done.

 

[savagedasher]

Jim I have found as much as a full gr difference in my Dasher Lapua brass.
I haven't tried anything larger. HINT HINT Larry

 

[jimcasey01]

Larry, I would love to weight sort your brass but.....but.....a...a.ah.......... my wife (and myself) decided I should at least act like I have a real life, got to keep up appearances for the neighbors.

 

[Joe Salt]

Larry after all that and a 3 ES what kind of groups are you getting at 1000 yards. I've never sorted by volume, but think I'm going to give it a try this winter. I've never shot under 4" with Ten shots but every once and a while they know I'm there. I've never gotten under a 6 ES but it did shoot good scores. You guys always keep me thinking! WHAT IF I TRIED THIS.

Joe Salt

 

[savagedasher]

Joe My shooting at 1000yd is not something I have done much on paper. 5'' is my best. In practice with good conditions 3.25 is my best with 5 shots.
My 15 year old Grand Daughter Her first and only 1000yd paper shoot shot 7.7 ''10 shot with 3''of vertical,
600 yd I shot 1.059 and 1.652 both had 3/4''of Vertical.
Internal case capacity is the reason for my low ES numbers. Before I did it my ES was 10 to 14.
Jim did a great service with the 223.
By using his figures I doubled the numbers and I used OL with 200gr bullet in a 300 win .
My friend who shoot them have numbers on ES from15 to 50.
I will be working with a friend with 300 win in a couple of weeks I will post the results.

Also remember we are shooting in Florida and 75 year old eyes don't help.
Larry

 

[tonysnoo]

This thread got me wondering si I tested some new lapua I have. I expected there to be some pretty big variables because it was 308 Palma brass that I sized down to 6SLR and neck trimmed to .014 wall. I fired them once and full length sized them. Then I went through the process of weighing them to the nearest .1 grain.

I weighed 98
7 weighed 170.4 - 170.5
23 weighed 170.6 - 170.9
41 weighed 171 - 171.4
19 weighed 171.5 - 171.9
8. Weighed 172 - 172.5
So roughly 2 grains separated the lightest from the heaviest.

Then I filled each case with water level to the top...perfectly flat tension line. What a pita....

The results were surprising. I found no patern at all. I measured

4 @ 53
27 @ 53.1
44 @ 53.2
20 @ 53.3
3 @ 53.4

The few that we're the lightest and heaviest came from mid weight cases. Overall .4 grains of water vs 2 grains of empty brass.

I know one sample of brass does not make any hard fast rule, but it was interesting to see....for what it's worth......

 

[dmoran]

The results were surprising. I found no patern at all.

The few that we're the lightest and heaviest came from mid weight cases. Overall .4 grains of water vs 2 grains of empty brass.

Thanks for sharing your time spent finding the truth to your cases.....

Your results of "no pattern" is very typical of what I see more times then not (from many different cartridges over many years).
Myself, I qualify cases, and do not segregate them, and only cue out extremes.
Your "Overall .4-grains" spread is good for that size case, and myself I would not cue out any........


Good Luck
Donovan

 

[mikecr]

Thanks tonysnoo
That is inline with but more consistent than I usually find. It would be challenging to do any better.