Rifle firing upon closing the bolt, without firing pin being actuated

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pacobillie

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This is about a mishap that I recently experienced. Fortunately, the rifle was pointed down range and there was no injury to either persons or property.

I was at my local range, trying out some loads in a new to me rifle. The rifle is a Weatherby Vanguard S2, chambered in 257 Weatherby.

All rounds fired were my own reloads. The primers used were Federal LRM Match primers. This had never, ever happened to me, although I have reloaded tens of thousands of rifle and pistol rounds.

Everything went well with the first 10 rounds. Upon chambering the 11th round, the shot went off as I was closing the bolt, although there was neither body part, nor object making contact with the trigger. Upon examination of the fired round, the primer expanded into the firing pin hole, thus supporting my assumption that there was no inadvertent release of the firing pin.

I can only surmise that chambering the round caused the priming compound in the primer to be squeezed in such a way that it went off. This is even stranger since I did not slam the bolt shut, but rather closed it fairly gently. The only other thing that I can think of is some kind of hard debris between the bolt face and the primer causing the primer to ignite upon closing the bolt.

Has anyone experienced this? Any other ideas?
 
I'm not sure a high primer would cause the problem, closing the bolt would just seat the primer flush with the base of the case "normally".

But two things do come to mind, defective anvil, tilted anvil or firing pin stuck in the fired position.

I had a SKS go full auto when a piece of brass jammed the floating firing pin forward.
 
Not sure how sensitive Federal primers are...Lee had a warning for a long time not to use them in their hand primers.
I never use them so can't say.
 
bigedp51 said:
I'm not sure a high primer would cause the problem, closing the bolt would just seat the primer flush with the base of the case "normally".

But two things do come to mind, defective anvil, tilted anvil or firing pin stuck in the fired position.

I had a SKS go full auto when a piece of brass jammed the floating firing pin forward.
Click to expand...

He already discounted the firing pin and a tilted anvil is as likely to go off during seating as it is any time else. High primer is just my best guess. Not much makes sense if all said by the OP is the case.
 
bigedp51 said:
I'm not sure a high primer would cause the problem, closing the bolt would just seat the primer flush with the base of the case "normally".

But two things do come to mind, defective anvil, tilted anvil or firing pin stuck in the fired position.

I had a SKS go full auto when a piece of brass jammed the floating firing pin forward.
Click to expand...
,

I doubt it was a high primer, since I examine all primed cases and did not notice. If it was a stuck firing pin, the detonation must have set it back, since the primer expanded into the firing pin recess.
 
Federal primers are noticeably more sensitive. The rollers on the bottom of my chair set them off. But not the other brands.

But it is very hard to imagine that a high primer would fire. It would just seat flush.

Unless the reason it was high was that there was something else in the pocket.

Can you carefully deprime and see if there is debris on the pocket?
 
Ganderite said:
Federal primers are noticeably more sensitive. The rollers on the bottom of my chair set them off. But not the other brands.

But it is very hard to imagine that a high primer would fire. It would just seat flush.

Unless the reason it was high was that there was something else in the pocket.

Can you carefully deprime and see if there is debris on the pocket?
Click to expand...

I will do that, but if there is anything stuck in there and it is loose, it might just fall into the primer collection tube.
 
pacobillie said:
I will do that, but if there is anything stuck in there and it is loose, it might just fall into the primer collection tube.
Click to expand...
I just ran the casing through the decapping die. I had emtied the collection tube just prior. There was no debris in the primer pocket, but the anvil looks to be tilted. One of the three legs is definitely recessed from the rim, and a corner of the other two is sticking out beyond the rim.
 
pacobillie said:
I just ran the casing through the decapping die. I had emtied the collection tube just prior. There was no debris in the primer pocket, but the anvil looks to be tilted. One of the three legs is definitely recessed from the rim, and a corner of the other two is sticking out beyond the rim.
Click to expand...

Sounds like biged nailed it. Very weird that you got through priming and despite you checking for high primers it was set off by chambering...
 
Out of curiosity... ball powder or extruded?

Ball powder would work its way through the primer pocket and give the anvil a solid base if the primer got seated deeper while chambering.
 
Tex Critter said:
May very well have been a cocked primer, but I have never seen one set off by merely fully chambering a round.
Click to expand...

A priming tool would push on the primer just like the bolt face would when closing the bolt and I think when the OP felt resistance he stopped seating with the priming tool. This left the primer seated high and the pressure from the bolt face set the primer off with the tilted anvil. "OR" something caused the firing pin to be locked extended in the fired position and set off the primer. Both of these are just guesses on my part and only the OP will have a better idea of what happened.

With a normal primer it is seated below flush with a preload on the anvil.

oiIRxun.jpg
 
Or the rifle. A 'New to Me' rifle might have had the trigger worked on by someone else to the point of being occasionally unsafe and going off. Probably more likely than a primer tilted.
 
Al-Sway said:
Or the rifle. A 'New to Me' rifle might have had the trigger worked on by someone else to the point of being occasionally unsafe and going off. Probably more likely than a primer tilted.
Click to expand...

It was purchased from a member on the EE with a good trader rating. So, hopefully, that is not the case.

As I mentioned in the opening post, the primer expanded into the firing pin recess, suggesting that the trigger was not released. No other fired primers looked like that.
 
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