Blown Primer

Discussion in 'Main Message Board' started by bench, Jun 18, 2017.

  1. bench

    bench Silver $$ Contributor

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    How do you blow a primer out of the case,how can there be room for a primer to fall out of the brass.
    I just had it happen the other day and am stumped how if head space is correct does this happen.
    Primer looked like a new one other than being fired and without measuring the brass it looks good also.
    Out of town and have not had time to double check anything yet
     
  2. DaveTooley

    DaveTooley Silver $$ Contributor

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    Easy you exceeded the yield point of the brass. Swollen head.
     
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  3. bench

    bench Silver $$ Contributor

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    So I guess the primer falls out when you start to eject the spent round not actually when its fired??
     
  4. Ggmac

    Ggmac

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    Yes
     
  5. RonAKA

    RonAKA

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    The primer initially pops out to the extent the headspace allows on every firing. However, the primer is pushed back in again as the case is forced against the bolt head. It normally stays there and looks like it has never moved after firing. But, if the primer pocket is too large from over pressure the primer will simply fall out when the case is ejected from the action. See the animation at this link to see what happens on firing.

    http://www.varmintal.com/aengr.htm#ActionAnalysis
     
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  6. Shaggy357

    Shaggy357

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    ^^^ What he said. 22 Hornets are notorious for this if loads are too hot. Don't have to deprime. Don't have to reprime. Brass is trash. If you have spent primers falling out of brass, the primer pockets have been stretched or someone has "uniformed" them oversized....pinch the cases with a pliers and save for the scrap man.

    Steve :)
     
  7. bench

    bench Silver $$ Contributor

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    Thanks guys for the info
    Will back off on powder charge
     
  8. Shynloco

    Shynloco You can lead a horse to water, but ........ Silver $$ Contributor

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    Amen to that! Discovered that first hand the other day when I blew one out using Norma Brass in my 260 Remington while testing loads. Funny thing was that the same identical load, same components (CCI Large Rifle and VVN150), same rifle using Lapua Brass, held just fine with ZERO signs of pressure. And the load was within the limits of a recommended load in the Sierra Manual, not a "hot load." I haven't experienced a blown primer in years and that taught me simply that Norma Brass cannot withstand the same pressures that Lapua does.

    Alex
     
  9. Shaggy357

    Shaggy357

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    Have you compared case volume? If Norma brass is a little thicker, it will have less case volume and will build pressure faster. It is surprising how much difference there can be in case volume when comparing lot to lot variation or brand to brand variation. In a couple of my 7TCUs, the load in Winchester brass is half grain higher than same load in a WCC brass. The military brass is thicker with less volume. Half a grain of powder less, but same velocity and accuracy. Something to think about. Changing brass, or primers, or lot of powder, can take a load from mild to wild. May even cause primer pocket stretch which allows the primer to fall out.
     
  10. mongo chicago

    mongo chicago

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    A friend had a blown primer with Hornady factory ammo in 22-250. Match chamber new barrel. Only happened with a certain lot.
     

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