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What, Rifle primers fit.

Discussion in '10mm Reloading Forum' started by JTknives, Sep 14, 2010.

  1. JTknives


    Dec 1, 2009
    Today I picked up some Winchester large rifle primers to reload some 500 S&W. I looked at the primers and could swear thy where large pistol primers. I thought what the hell and seated one in a used 10mm case. What, it seated perfect and did not stick up at all. I then thought maybe it had somthing to do with it being used brass. So I grabbed a new starline case and seated a rifle primer. And I got the same results as befor, perfect seating. Now I'm using only starling brass so I don't know if other brass will fit a rifle primer. Another thing I'm wondering is do I gain anything from being able to use large rifle primers.
  2. MSgt Dotson

    MSgt Dotson

    Sep 30, 2006
    There is some overlap on LP and LR primer specs, but, I'd not casually interchange them, and certainly not with the warmer 500 S&W loads....

  3. MakeMineA10mm

    MakeMineA10mm * * * * Millennium Member Lifetime Member

    Feb 13, 1999
    Central Illinois
    Yep, "upgrading" to rifle primers can increase your pressures up to 5000psi with the same load. That's hot enough to go well into the danger area (no safety margin left), so not a good idea. If you develop the load from below the manual's starting load and watch your pressure signs smartly, there's no reason you can't develop a load with them, but don't expect to magically get more pressure out of the round.

    In other words, the 10mm can easily get to it's max pressure with pistol primers, and going over that pressure with a hotter primer will violate the laws of internal ballistics just as much as seating the bullet deeper or using more powder.

    I see it as something that can be done in a survival situation when LR primers can be found but no LPs...

    And, I tried (back when I was younger and not as informed) LR primers in the 10mm, and got no real added benefit from them.
  4. jimhoff


    Aug 6, 2006
    Rifle primers are a bit thicker and 500 S&W uses rifle primers because of the extra high pressure of that round. So a light fire-pin might not cap 'em off. I think they might not seat as deeply in the pocket - by a few .001's
  5. _The_Shadow

    _The_Shadow Ret. Fireman

    Jul 23, 2007
    Southeast, LoUiSiAna
    Large rifle primers are ever so slightly longer and if seated in a larger pistol primer pocket they stick out like they aren't fully seated. If used in some semiautos there is the possibility of a slam-fire!

    According to SAAMI, the depths for small pistol, small rifle, and large pistol primer pockets are .118" to .122", while large rifle primer pocket depths are .128" to .132". Small pistol and small rifle primers have the same diameter (.175") while large rifle and large pistol primers are also the same (.210").

    Also, Speer recommends primers be seated .003" to .005" below flush.

    Attached Files:

    Last edited: Jul 13, 2011
  6. glock20c10mm


    Dec 4, 2004
    Out West
    Does that mean "flush" or ".000?" under flush?