Measuring case capacity?

Discussion in 'Reloading' started by LRHWAL, Mar 12, 2010.

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    LRHWAL Well-Known Member

    Jan 11, 2006
    I admit to trying this only once with a fine ball powder as recommended by Jerry Theo. I've searched on the net on this quite a bit, but got to wondering (again as I do from time to time):rolleyes:

    If ES is as low as you are happy with (and I acknowledge that this smacks of accepting mediocrity), is anything to be gained by measuring capacity?

    In other words does variance matter to accuracy in any respect other than muzzle velocity?

    I ask as I did a very small sample test of our locally made brass, with thicker necks and although the variation is more than my sorted and "touch turned" WW, I nevertheless achieved great ES numbers so far (over 4 loads).

    I'm wondering whether I'd be any worse off with this brass if I turned the necks a touch to even them out, when compared to my sorted WW. I'm thinking probably not, but I would need to see how runout progressed with cases that have potentially thinner and thicker sides in the body...

    Thanks for any thoughts on this. Speculation is welcome too!
  2. Mikecr

    Mikecr Well-Known Member

    Aug 10, 2003
    Is there anything wrong with it?

    Yes, your barrel time/tune.

    This is pretty much unrelated to case capacity.

    Why not Just measure H20 capacity and match em?
    No weighing of brass, crude comparisons with powders, or other shortcuts...
    It's a simple thing to do.
  3. Gene

    Gene Well-Known Member

    Jan 23, 2007
    Filling cases with water and weighing is the normal method to determine capacity. You can cull out the extreme weights or use them for practice.

    Skim turning necks is always beneficial when done properly, and will result in more consistent neck thickness. In a factory chamber, the improvement may be negligible.

    LRHWAL Well-Known Member

    Jan 11, 2006
    I'm always amazed at how many new threads start up when you are away for a bit. It took me a while to find this again.

    Thanks for the replies.

    MikeCR, I think maybe we went past each other a bit. Yes, I agree barrel timing and harmonics are affected - but I think only because velocity is affected (or am I wrong on this??).

    I'm thinking that if ES is really low (lets pick an arbitrary low number like less than 5FPS for 20 shots), measuring capacity doesn't matter, as capacity only has an effect on velocity. This is really my question, if it's not affecting ES, does it matter at all and can capacity affect something other than MV?

    I'm guessing if pressure builds slower or quicker you'll see it in the MV numbers. I'm headed towards wondering how much capacity variation is actually relevant and at what point the variation is worth worrying about. Yes, I agree, nothing wrong with it, but there's this laziness thing....:D

    Gene, I agree on skim turning and found that it actually made a difference.

    Lastly, whats the easy (least messy) way to measure with water. I'd reseat a spent primer back to front and weigh it before seating, but filling to a consistent level bothers me. Is the drop of detergent the best it gets?

    Thanks again!
    Last edited: Mar 30, 2010