Case Capacity

[kyreloader]

I have read postings about measuring case capacity using ball powder, so I did so with my 6.5x47 cases this weekend. My question is how much difference in case capacity can you see on the target? To what capacity to you sort your lots?

Here are my results with measuring of 50 6.5x47 Lapua cases that have had all work done except taking out the old primer(meaning annealed, trimmed, resized, tumbled).

Case capacity of H335 in grains/ # of cases
49.7 - 1
49.8 - 2
49.9 - 0
50 - 9
50.1 - 2
50.2 - 7
50.3 - 6
50.4 - 3
50.5 - 4
50.6 - 5
50.7 - 5
50.8 - 3
50.9 - 2
51 - 1

The average of the capacity was 50.347g with a SD of 0.314 and ES of 1.3g.

I usually shoot Mid-Range F class with this rifle, so I have not thought much about case capacity before. I havent felt like I could shoot the difference. I am shooting in a different competition this winter where increased precision/accuracy is needed and I am trying to optimize my loading of those 20 cases. I plan to pull out my 20 best cases.

I pulled out my cases that had capacity of 50, 50.1 and 50.2g to keep together as a batch.

Your thoughts?

Thanks.

 

[kyreloader]

dmoran are you out there?

 

[fredhorace77]

i number my sticks in their individual sets, and go to load work. sometimes I will catch one that flys, and keep my eye on that piece.
Tom

+1...this is actually the best way to sort a case...load them up and watch them...if you get a flyer or high or low velocity...set it aside and mark it....if it does it second time...cull it out

oh..yea...IMHO

 

[TheSnake]

Now for some possible bad news ......
If you resized them with the primer in, there will be a strong possibility they got wrecked. Resizing without knocking the primer out can seriously hurt the primer pockets.

Dmoran,
I am trying to wrap my head around this statement. If the case head were resized entirely down to the base of the case, I could understand this easily. But the majority of the case head where the primer pocket lives is sitting in the shell holder below the base of the die and is not affected by resizing. I also imagine if resizing made that much of a difference on the primer pocket size, then FL resizing would tighten up a loose primer pocket every time the case is resized. I know there must be an AH HA moment here somewhere, but I dont understand it. Can you please explain so I can understand it? I don't resize without knocking out the spent primer but I do want the understand why this would make a difference.

Thanks.

 

[kyreloader]

kyreloader -

I myself cue out the extremes and keep the most I can.
That is a fairly big spread and more then I typically would see in that size case. I like to end up under .3-tenths spread with the smaller Lapua cases.
I do re-weigh all highs and lows to make sure they were not subject of procedure/human error.
And I to advise as Tom alluded to, to start out by re-weigh a few several times, to check your procedure is accurate and defined.

Now for some possible bad news ...... you stated:
"all work done except taking out the old primer(meaning annealed, trimmed, resized, tumbled"
If you resized them with the primer in, there will be a strong possibility they got wrecked. Resizing without knocking the primer out can seriously hurt the primer webbing.
Beware of this when seating new ones, if they are now loose and/or if the primer protrudes, they are wrecked.
If this ends up being the case, and the webbing did get stretched, it could explain the large spread to capacities.

Keep me posted....
Donovan

I use a Warner resizing die made from 3x fired cases with minimal sizing made. My regimen includes annealing, lubing, resizing with my Warner FL sizing die, tumbling, trimming, chamfering, removing the old primers with decapping die, cleaning/uniforming primer pockets then seating bullets. I have used this process for the life of the brass and these 300 cases are on their second barrel now. I would suspect over 10 loadings per case.

I have absolutely no problems with the primer pockets, neither loosening nor protruding as you state.

Lastly, I weighed my first case 3-4 times to make sure my process was consistent and every 10th case I weighed 3-4 times verifying my process. I was weighing with a Chargemaster, so not sure if that introduced some error into the system.

I will group in 0.3g batches and shoot them together.

Thanks.