Blown primers?

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  • Blown primers?

    Hi All,

    I was working on developing a load for my .308 this afternoon and encountered something new to me.

    About half way through the ladder test, I fire a round and the receiver smoked up a lot more than usual.

    Extracted the round and discovered a firing pin-sized hole in the primer.

    This happened twice more - on one occasion a wad of primer wound up inside the bolt.



    Left to right ... CCI primer in Win brass, Rem primer in new Lapua brass, Rem primer (with a hole in it) in new Lapua brass.

    This was a first outing for Remington primers for me (only purchased because the LGS was out of CCI)..

    Blow outs happened at 42.5 & 43 grains of AR2208 in a test running from 41 to 44 (max load suggested by ADI for 190 grain pills).

    Has anyone else encountered this with Remington primers?

    Cheers,

    Benn

  • #2
    Originally posted by RNFP" post=24369
    Hi All,

    I was working on developing a load for my .308 this afternoon and encountered something new to me.

    About half way through the ladder test, I fire a round and the receiver smoked up a lot more than usual.

    Extracted the round and discovered a firing pin-sized hole in the primer.

    This happened twice more - on one occasion a wad of primer wound up inside the bolt.



    Left to right ... CCI primer in Win brass, Rem primer in new Lapua brass, Rem primer (with a hole in it) in new Lapua brass.

    This was a first outing for Remington primers for me (only purchased because the LGS was out of CCI)..

    Blow outs happened at 42.5 & 43 grains of AR2208 in a test running from 41 to 44 (max load suggested by ADI for 190 grain pills).

    Has anyone else encountered this with Remington primers?

    Cheers,

    Benn
    Load development should involve the same components.

    CCI primers are the hardest, and will, as a rule of thumb, handle higher pressure than other brands.

    I don't do ladder tests, as there is not enough individual feedback to asses pressure signs.

    Thanks,

    Oddball

    Comment


    • Guest's Avatar
      Guest commented
      Editing a comment
      Sorry for the misunderstanding ... the CCI-primed case was not from today's ladder test. (I'm well aware of the need to only change one variable at a time.)

      I included it in the photo for comparison against how the Rem primers perform.

      Cheers,

      Benn

  • #3
    The load could be on the limit for your combination, but probably just the primers, there didn't look like there was any pressure signs except for the primer with a hole in it. Some primers are just softer than others, and maybe your rifle is getting a solid strike on them. I would try another brand before you damage the pin and bolt face.NBT

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    • Guest's Avatar
      Guest commented
      Editing a comment
      The case on the left and the middle clearly show flattening of the primer, the one on the right does not but has the primer punched..

      Did you crony the projectile speeds to see if it was in the ball park of what the ADI manual indicates..?

  • #4
    its not uncommon for you to be in the middle of the powder charge range, yet find a pressure problem.
    I encountered that again the other day.
    my howa 250 shoots wonderfully tight groups with 35gr of powder, but shows pressure signs yet max listed in ADI book is 36gr.
    currently checking my case lengths and neck tensions now before I drop 1/2 a gr of powder out.

    Comment


    • #5
      Originally posted by RNFP" post=24369
      Hi All,

      I was working on developing a load for my .308 this afternoon and encountered something new to me.

      About half way through the ladder test, I fire a round and the receiver smoked up a lot more than usual.

      Extracted the round and discovered a firing pin-sized hole in the primer.

      This happened twice more - on one occasion a wad of primer wound up inside the bolt.



      Left to right ... CCI primer in Win brass, Rem primer in new Lapua brass, Rem primer (with a hole in it) in new Lapua brass.

      This was a first outing for Remington primers for me (only purchased because the LGS was out of CCI)..

      Blow outs happened at 42.5 & 43 grains of AR2208 in a test running from 41 to 44 (max load suggested by ADI for 190 grain pills).

      Has anyone else encountered this with Remington primers?

      Cheers,

      Benn
      Left case is normal, middle case shows signs of high pressure (cratered primer), right case with blown primer is too hot a load for this rifle / cartridge components combination. Your powder charge should be reduced to something below whatever the middle load was for regular use if using those same components.
      It is best to stick to one combination of components when working up a load and if you change anything then start again with a light powder charge and work up and STOP at the middle case.
      This post may be fact or opinion, it is up to you to decide which.

      Comment


      • Spurious
        Spurious commented
        Editing a comment
        Here's some information that dispels some of the myths about pressure signs, and blown primers.

        Well worth the ten minutes to read . . . . .


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    • #6
      You will always get higher pressure from lapua brass compared to Winchester, federal or remington brass. Simply because the walls of the case are thicker which means the volume inside the case is less.

      Comment


      • #7
        What the picture is depicting is actually primer blanking, sometimes incorrectly referred to as pierced primers.
        It is clear that you don't have massively high pressures due to the primer edges still being relatively rounded.
        Primer blanking happens when there is insufficient firing pin impulse or momentum to contain the pressure acting on the primer cup material.
        Obviously softer or thinner material in the cup will increase the likelihood of primer blanking where the firing assembly has insufficient inertia to contain the pressure.
        The likely culprit is relaxation of your mainspring or in some cases increased friction of the firing assembly due to lack of lubrication, corrosion or unusual friction if say the firing pin is bent or distorted.
        The answer is to replace your mainspring or at least dismantle the bolt and look for anything that doesn't look or feel right.

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