Primer Pictures -- Pressure Opinions?

Discussion in 'The Ammo & Reloading Forum' started by Josh Smith, Feb 1, 2012.

  1. Josh Smith

    Josh Smith Member

    Nov 10, 2009
    Wabash IN
    Hi Folks,

    I went from 0.318" bullets to 0.323" bullets in my Gew88/05 Commission rifle. The 0.318" bullets were just causing problems.

    Here are some pictures of primers. The brass is 7.92x57mmJS (8mm Mauser) formed from Winchester .30-06 brass. Bullets are 150 grain Hornady. Powder charge is 43.5 grains of Varget, and primers are Federal Large Rifle. Published velocity for this load is 2400fps, which is just fine. Figure it might be a bit more with the tight bore.

    Two different exposures with their inverted images on the right side

    Macro uncut

    The primers look like they're fine to me. Do you agree?

    Data is from Hornady and the 43.5 grains Varget is their starting load. Hodgdon's starting load is 45.5 grains. Figure I'm safe using 43.5 grains as a start and 46 grains as max -- do you agree?

    Also, this is effectively a squeeze bore. The initial slugging of the bore resulted in a groove measurement of a little over 0.318", but subsequent cleaning and shooting have been peeling off grime to reveal something a bit bigger. I still need to slug it again, but it may end up being 0.321" as they were playing with sizes of 0.318" to 0.321" while developing the rifle, and I have an original 1892 barrel. For now I'm assuming a groove diameter of 0.318" to be safe.

    Would you have an estimate to what kind of velocity the barrel adds if it's 0.321"? I'm not trying to push the rifle's limits at all; just curious. I know there were squeeze bore barrels made for the .22LR before the advent of the rimfire .17 calibers, and they boosted by a few hundred feet per second.

    Subjectively, recoil is about like a .30-30 with 150 grain load, maybe a bit less. Feels good to shoot and if I can find an accuracy node someplace under 46 grains Varget, I'll be a very happy camper.


  2. cycloneman

    cycloneman Well-Known Member

    Dec 16, 2008
    Better give this some time and keep checking back. You should get some good advise before proceeding. LD will probably chime in tomorrow morning. I think something is amiss. But i dont have the knowledge some other have. Hang tight.

  3. Josh Smith

    Josh Smith Member

    Nov 10, 2009
    Wabash IN

    Will do.

    I believe it's showing slightly low pressures, right where I want it in fact.

    I'd love to have a piezo gun about now..!


  4. Bindernut

    Bindernut Well-Known Member

    Oct 24, 2007
    ND, USA
    From how I'm reading the primers, you're just fine pressure-wise. They've got nice rounded pin impressions and flattening at all that I can see.
    If the load is warm enough to seal the case neck so there's little or no soot-blow-by then I'd say you've got a good safe load.
  5. JLA

    JLA Well-Known Member

    Feb 26, 2007
    Heart Of Texas
    Looks ok to me. There are no extrusion marks on the headstamp either and the primers have nice round edges. Id say that load is right where it should be despite the oversized bullet.
  6. myfriendis410

    myfriendis410 Member

    Mar 30, 2011
    Lompoc California
    The primers look fine, but how does the neck look? Is it blackened? That would indicate low pressure and something to be leery of.
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