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

[dcali]

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.

 

[Jdne5b]

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.

 

[Raythemanroe]

Triggers can get junked when you blank primers.

Ray

 

[243Lapua]

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

 

[Dusty Stevens]

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

 

[rammac]

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.

 

[Jdne5b]

Picture of the case/primer?

Swap trigger and firing pin spring and shoot it again.

 

[dcali]

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:

 

[Dusty Stevens]

Man thats weird. Like a double strike or bounce

 

[Jdne5b]

Man thats weird. Like a double strike or bounce

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.

 

[Dusty Stevens]

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.

I guess decapping it would show that

 

[hogpatrol]

Have you borescoped the barrel?

 

[Ggmac]

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

 

[dcali]

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.

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.

 

[dcali]

Have you borescoped the barrel?

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

 

[dcali]

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

All the other cases look normal.

 

[Raythemanroe]

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

 

[wedgy]

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.

 

[geo.ulrich]

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:

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.....

 

[dcali]

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.....

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.