Case weight

[RustyRick]

I did a first. I bought a box of 50 new brass. Primed them and weighed them. I got a spread of 4.3 GN.

Is that kinda normal? Is that a lot? Or should I try to split into weight groups.

 

[ohiohunter]

I did a first. I bought a box of 50 new brass. Primed them and weighed them. I got a spread of 4.3 GN.

Is that kinda normal? Is that a lot? Or should I try to split into weight groups.

Shouldn't have primed them.

I shoot lapua brass (if available) and I don't sort brass.

 

[Dosh]

RR, I weigh after case prep and polish since some may trim more than others. The higher quality brass is more consistent in weight, primer pockets etc. I like Lapua and Norma.

 

[Barrelnut]

Primers can vary in weight but not that much, in my experience anyway. I have weighed Federal match primers.

I would shoot them in groups sorted by weight if you are looking for the lowest es/sd.

 

[RustyRick]

I checked case length and they were all VG. These were new never fired cases.

 

[tbrice23]

4.3 grain spread is a lot of variance.
I have 400 pieces of winchester 300 wm brass that the spread is 5 grains. UN PRIMED
I fully prep and fire form before sorting by weight. Trim, primer pocket uniform, flash hole deburr, neck turn.

 

[benchracer]

I did a first. I bought a box of 50 new brass. Primed them and weighed them. I got a spread of 4.3 GN.

Is that kinda normal? Is that a lot? Or should I try to split into weight groups.

Awhile back, I posted a thread on this forum asking how closely case weight correlates to internal volume. No one seemed to have a definitive answer.

Recently, I tested around 100 milsurp 30-06 cases, from the same headstamp and production lot, all fired from the same rifle. I weighed each case, then measured the actual internal case capacity in grains of water. All but a handful of cases fell within + or - 1 grain of the overall average (70.2 grains). Of the cases that fell outside that range, only one of them would have been detected by weight sorting the cases. I found no correlation between case weight and internal volume.

Based on my own experiment, I believe the only effective way to sort cases is to actually measure the internal volume of each case and sort accordingly. I believe the best way to do this would be to use once fired brass that has been re-sized in your preferred manner (full length or neck -sized), with the de-capping pin removed to leave the spent primer in the case. The cases should then be trimmed to a uniform length, measured for volume, and sorted accordingly.

 

[RustyRick]

Wow - what a treasure hunt to find the source of flyers. I'll weight sort 10 bullets/projectiles. Then take 5 of the lightest cases and 5 of the heaviest cases and run past an accurate chronograph and see if I find any velocity differences.

 

[Barrelnut]

Awhile back, I posted a thread on this forum asking how closely case weight correlates to internal volume. No one seemed to have a definitive answer.

Recently, I tested around 100 milsurp 30-06 cases, from the same headstamp and production lot, all fired from the same rifle. I weighed each case, then measured the actual internal case capacity in grains of water. All but a handful of cases fell within + or - 1 grain of the overall average (70.2 grains). Of the cases that fell outside that range, only one of them would have been detected by weight sorting the cases. I found no correlation between case weight and internal volume.

Based on my own experiment, I believe the only effective way to sort cases is to actually measure the internal volume of each case and sort accordingly. I believe the best way to do this would be to use once fired brass that has been re-sized in your preferred manner (full length or neck -sized), with the de-capping pin removed to leave the spent primer in the case. The cases should then be trimmed to a uniform length, measured for volume, and sorted accordingly.

I did this same test a few months ago with Hornady 6.5 Creedmoor brass and Norma 300 WSM brass. Ran the test on the Hornady twice. Did this cause of some of the preaching Mickcr does concerning weight versus volume sorting. I found in all three test that 8 out of 10 cases were sorted correctly by weight measurement. 2 of the 10 were not correct if volume measurement was used. My conclusion ---- weight measurement is probably about 80% accurate. Is it perfect? No. Do I care? Only when I'm prepping for a 800 yard shot at an elk.

Oh and all were once fired and not resized. I left the spent primer in as the plug. Count was 50 cartridges each.

 

[RustyRick]

Just to be the devils advocate - the water would need a drop of soap in it to break the surface tension. So it fill to the neck flush and not a 1000 over. Boy I can't believe I'm getting so anal in my old age.

 

[Barrelnut]

Just to be the devils advocate - the water would need a drop of soap in it to break the surface tension. So it fill to the neck flush and not a 1000 over. Boy I can't believe I'm getting so anal in my old age.

I used a few drops of denatured alcohol as per CR's recommendations, I believe. There can still be a slight bulge at the top of the neck, but it is very predictable and you can always make it the same size if you are carefull. Also a good dropper helps. I used those that are long plastic and will fit almost to the bottom of the case.

You cannot be too anal when trying to lower SD.

 

[RustyRick]

Speechless - I just weighed most of a box of Berger 168gr VLD-H. WOW they ranged from a low of 167.9 to 168.1. Hats off to you guys at Berger.

 

[RustyRick]

Go to a veterinary supply store and buy a syringelightbulb.

 

[benchracer]

I did this same test a few months ago with Hornady 6.5 Creedmoor brass and Norma 300 WSM brass. Ran the test on the Hornady twice. Did this cause of some of the preaching Mickcr does concerning weight versus volume sorting. I found in all three test that 8 out of 10 cases were sorted correctly by weight measurement. 2 of the 10 were not correct if volume measurement was used. My conclusion ---- weight measurement is probably about 80% accurate. Is it perfect? No. Do I care? Only when I'm prepping for a 800 yard shot at an elk.

Oh and all were once fired and not resized. I left the spent primer in as the plug. Count was 50 cartridges each.

I ran the test the same way you did, checking 94 once fired cases. The overall variance in case weight was 8 grains, while the overall variance in internal volume was 3.9 grains.

91 of 94 cases had an internal volume between 69.2 and 70.4 grains. Of the three outliers, only one would have been an obvious cull by case weight alone. The case weight of the remaining 91 ranged from 192.6 to 199.5 grains. The three outliers weighed 200.6, 199.5, and 198.4 grains, having internal volumes of 68.8, 66.5, and 66.8 grains, respectively. Only one of them would have been an obvious outlier by case weight. 93 of 94 cases tested showed ZERO relationship between case weight and internal volume.

If uniform case volume is the objective, the only way to reliably achieve that is by actually measuring the volume. If you feel like you are accomplishing something by weight sorting your cases, go ahead. It's your time. Waste it how you wish.