once fired brass and load development

Discussion in 'Reloading' started by buckbrush, Jul 6, 2009.

  1. buckbrush

    buckbrush Well-Known Member

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    Nov 26, 2008
    I used all new brass to develop my load for my 7 mag which is a first. I usually just reloaded factory stuff I had shot. Now I only have about 10 pieces left before I get to the once fired stuff.

    Will I need to change anything when I get to the fired stuff? Thanks.
     
  2. J E Custom

    J E Custom Well-Known Member

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    Jul 29, 2004
    If you prepared the new brass (Sized,trimmed and deburred) just re size with the same setting.

    If you didn't prep then I would prep before the first reloading and the fact that the brass now
    fits your chamber I would ether neck size only or full length size just enough to make them
    chamber well. (This will make the brass last longer if not worked to hard).

    J E CUSTOM
     

  3. Katbird

    Katbird Member

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    Dec 24, 2008
    Be advised that there is normally a lot of play in the chamber of a factory magnum cartridge. The initial fireform can stretch brass to the point of nearing a case head separation. I always use new brass and open up the case neck to .308 and neck back down to 7mm slowly until there is a crush fit in the chamber. Brass lasts much longer this way. Just be sure to set up your dies to only bump the shoulder back no more than .0015. Most problems are caused by setting the shoulder back too far.
     
  4. buckbrush

    buckbrush Well-Known Member

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    Nov 26, 2008
    I have been using a Lee Collet Die to get the necks round since they were so beat up from bouncing around in the bag. I measured the diameter of the case at the shoulder of a fired case and it's about 0.008" wider than a new piece of brass.

    I was concerned since there is now obviously more case capacity, what that might require me to do with my powder charge.

    Thanks.
     
  5. Katbird

    Katbird Member

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    The chamber is obviously much bigger than unfired brass. Part of the energy in your fireform loads was spent just blowing the brass out to fill the chamber. You now have a slightly larger capacity case if you neck size-only. You can probably add a tad more powder to your load, but work up slowly. If you are using a chronograph, you can tell when you are at the point of diminishing returns. The velocity increases at a slower rate than the additional pressure caused by the higher powder charges. That's a good place to stop, if you haven't already met your maximum threshhold. My 7mmRemMag always shot best at maximum loads. good luck.