Pierced a primer, now it won't shoot. What to check?

Discussion in 'Gun Project Questions & Gunsmithing' started by damoncali, Aug 23, 2019.

  1. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    The other day my Borden tube gun (.308 Winchester) action *almost* pierced a primer. It got pushed back to flat, but didn't get punctured. I heard a ping, and the shot went 5-7 MOA to the right. After that, the point of impact dropped about .75 MOA, and it went from shooting in the .2s - .5s to no better than .75 MOA, with several three shot groups between 1-2 MOA.

    I haven't tracked down the reason for the primer mishap. I'm going to double check my dies, but I'm 99.9% that they're sizing .002. This was primer number 800ish out of a box of 1000 with no issues. The load was hot, but not the highest I've shot through this rifle, even on that day.

    I pulled the bolt apart. There is nothing obviously wrong. Since the primer didn't actually blow, there's no primer disc floating around. A dial indicator on the firing pin shows that it runs out .005-.007" at the tip (the fat part of the pin is .001"). Jim doesn't think that's the problem. The trigger is a CG two stage. I pulled it apart and nothing is broken. The cover plate screw was slightly loose, but I'm not sure how popping a primer would cause that. The drop in accuracy/change in impact was immediate and significant.

    Before I just give it all a thorough cleaning and put it back together, is there anything else I should be looking at?

    Edit: None of the obvious stuff was loose - scope rings, action screws, etc.
     
    Last edited: Aug 23, 2019
  2. Jdne5b

    Jdne5b Gold $$ Contributor

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    I'd be checking something mechanical. Scope, action screws, trigger hanger(if they have one), scope base/rings. Maybe its unrelated to the "ping" and flat primer.
     
  3. Raythemanroe

    Raythemanroe Bullet Whisperer Silver $$ Contributor

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    Triggers can get junked when you blank primers.

    Ray
     
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  4. 243Lapua

    243Lapua Silver $$ Contributor

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    Heard a Ping. It was a hot load.I would check the Firing Pin spring. Just never know that a coil broke.
     
  5. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    Something could have cracked in the trigger and you cant see it. Id be looking at your mechanical parts- scope system, trigger, bolt
     
  6. rammac

    rammac

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    I'd also check the recoil lug to see if there has been movement between it and the receiver or the stock. If your lug is pinned then I'd check the pin.
     
  7. Jdne5b

    Jdne5b Gold $$ Contributor

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    Picture of the case/primer?

    Swap trigger and firing pin spring and shoot it again.
     
  8. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    I'm definitely going to swap out the trigger. I don't see anything wrong with the firing pin or spring, but who knows. Here's a close up of the primer:
     

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  9. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    Man thats weird. Like a double strike or bounce
     
  10. Jdne5b

    Jdne5b Gold $$ Contributor

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    What are the chances it did pierce and the cup wound up back in the same spot? Looks like a ridge/seam around the edge.
     
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  11. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    I guess decapping it would show that
     
  12. hogpatrol

    hogpatrol Don't criticize the farmer with your mouth full. Gold $$ Contributor

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    Have you borescoped the barrel?
     
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  13. Ggmac

    Ggmac Gold $$ Contributor

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    Have you checked the round fired before that one ? That imprint looks weird, almost like what Dusty said or a primer cup that was stuck to the bolt face or firing pin and when fired on this case the blank was actually imprinted in this primer . Just a guess
     
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  14. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    I hadn't thought of that. I'll take a closer look.

    Edit: I decapped the case, and pulled the anvil out of the primer. I do not think it's a disc that got blown back into the hole. The inside of the cup has the normal indent from the anvil, but it's flat on the outside except for the slightly raised ring from the firing pin hole in the bolt. The normal firing pin dent is completely flat on the outside.
     
    Last edited: Aug 23, 2019
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  15. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    I did, but only for the usual cleaning purposes. What would you be looking for specifically in this case? It looked normal.
     
  16. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    All the other cases look normal.
     
  17. Raythemanroe

    Raythemanroe Bullet Whisperer Silver $$ Contributor

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    Yes, looking at the picture kinda looks like a blanked primer.. I would really go to town on making sure I didn't have anything floating around but would be ordering up a new trigger.

    Ray
     
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  18. wedgy

    wedgy Gold $$ Contributor

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    Could be the dreaded hard carbon ring in the throat that caused the pressure, and it usually ruins accuracy as well. If you have some longer cases that extend into the ring it gets worse. It will need JP paste or similar abrasive to get rid of it.
     
  19. geo.ulrich

    geo.ulrich beware of owner Gold $$ Contributor

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    Load isn't to hot primer edges are still have a radius that also rules out excessive shoulder set back. something definitely looks weird around the pin hit. As said before almost looks blanked or as if a disc was on and got shoved on top. also t.i.r.'s are fine can you get a shot of bolt face and firing pin tip.....
     
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  20. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    It's hard to get a picture of it, but it looks like the primer was hit, cratered a tiny bit, adn then was pushed back flat, but stopped when it got flat - not going all the way to shear off the disc. The outer, slightly raised circle is from the firing pin hole. The ding in the middle looks like it could be from the pin? But it's hard to say. It looks weird. No primers have been actually pierced in this rifle - so it's not like a disc got stuck in there.

    Bolt face and pin tip pictures attached.
     

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