Case weight

[Barrelnut]

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.

If I'm reading that correctly, we were about 180 degrees different in the test results. Mine would have sorted 80% correct by case weight and only 20% of yours did. May be the difference in the source brass, your mil spec 30-06 and mine Hornady 6.5 and Norma 300 WSM.

I numbered each case and recorded its weight and case volume, then sorted the results via spreadsheet. It was easy to pick out the couple of exact ones that sorted differently by weight versus volume.

Like they say your results may vary..... I am not exactly jumping up and down at the fact that 2 out of 10 pieces of my brass don't correlate. Cause I know that's one of the ones I will pull out when I need it the most. LOL. But for trying to work up a load or practice, I don't worry about it too much. I keep 50 cartridges of each that are golden. They are sorted by volume, annealed and have the same number of firings. The Berger bullets are also sorted by weight and bearing surface. These are what I am elk hunting with in eastern Oregon with this year. I'm a bad shot, I need all the help I can get...

 

[Elk868]

Hello all
if i understand that correct is the only way to get good acurracy to meassure internal volume ??
till now i not really cared about weight and internal volume of a case .
Most of Errors was made by myself i think .
Now my question :
how to measure internal volume properly and what you use for ??
is there a way to do it more easy ?
i own around 8-900 cases 338 LM . it would me drive nuts to do that with all my cases
Elk868

 

[Barrelnut]

Use fired cases with the primer still in them. This allows the cases to have more uniform dimensions on the outside which affects capacity on the inside. The primers act as the plug for the flash hole.

Need a bowl of water with few drops of alcohol to lessen water tension and a dropper that will fit down into the case some.

1) weigh the case
2) fill with the dropper
3) weigh case again
4) record the difference in weight.
5) You can lay out a piece of tape along the side of a table. Write the weights on it and stand the case up next to the corresponding weight as you go. After a while you will start to notice a bell shaped curve in the sorted brass. It will now be easy to see what the average weight is and the number of cases closes to the average weight. Shoot the cases with the closest volumes together.

 

[Mikecr]

Barrelnut's method is sound.
I've run into same correlation discrepancies as benchracer. Of course this changes by brass design, brass quality, and brass lot. I've also run across a lot of 100 6br brass that all matched.
I would never know if I did not actually measure capacity.

You can add a few drops of alcohol in a cup of water to reduce meniscus, and it's vital that brass was new to begin & not ever FL sized & fully fire formed & trimmed before measure. You want to find true baseline capacity matches.
Once you've ruined this with FL sizing & continued trimming, your matches fade away.

 

[rcoody]

this is a little off track but along the same line of sorting. I have tried it all. Never could convince myself that it helped that much but then again I wasn't loading for a benchrest rifle.

first my question is have you been able to really see a difference in group size with cases sorted by weight or volume?

next question is Have you ever sorted while shooting for cases that grouped together? In other words took out the flyers?

I have thought about that and then investigating what might be different or if it is repeatable by reloading the flyers and shooting them.

 

[BigSwede]

I just sorted 150 new 300win brass for my 7mm-300wm. 60% of them were 240gns +/- .4gns. 20% fell below by a grain and 20% were higher by a grain give or take .5gns. I don't think that's terrible. I have not measured case lengths nor primer pocket uniformity which may account for the discrepancies.

 

[Barrelnut]

I just sorted 150 new 300win brass for my 7mm-300wm. 60% of them were 240gns +/- .4gns. 20% fell below by a grain and 20% were higher by a grain give or take .5gns. I don't think that's terrible. I have not measured case lengths nor primer pocket uniformity which may account for the discrepancies.

No thats not bad. What brand brass?

 

[Barrelnut]

this is a little off track but along the same line of sorting. I have tried it all. Never could convince myself that it helped that much but then again I wasn't loading for a benchrest rifle.

first my question is have you been able to really see a difference in group size with cases sorted by weight or volume?

next question is Have you ever sorted while shooting for cases that grouped together? In other words took out the flyers?

I have thought about that and then investigating what might be different or if it is repeatable by reloading the flyers and shooting them.

I don't think 100 yards benchrest shooters sorts brass. I believe 600 yards and 1000 yard benchrest shooters do though.

I have shot in some 600 yard F class type stuff and sorting brass has bettered my scores. Sorting takes out the vertical in the groups. It is noticeable at 600 yards and beyond.

I have taken brass that shot a flyer and taken notice of what it did on the second firing. I couldn't reproduce it. I have taken brass that had lots of runout after loading, loaded it again and couldn't reproduce it. At a certain point, I think flyers are caused by the bullets and not the case.

 

[BigSwede]

Barrelnut---That was with winchester brass that came from gun broker in bags of 50