Had a real BLAST at the range today...

[papersoldier]

Helping my buddy christen his newly assembled AR-10 (.308) and we had some real fireworks to commemorate the occasion. Still no idea how this happened, but he's now down one magazine (blew apart) and I'm compulsively counting my fingers to make sure they're all there.

Here's my keepsake from the adventure:

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[Stomper]

Holy….. smokes!



That looks like it fired out of battery…. Yeah?

 

[Knobgoblin]

Very high pucker factor right there

 

[Certaindeaf]

Reloads?

 

[G1GRANDEUR]

I was thinking another meaning of BLAST at the range, good thing nobody got hurt.

 

[papersoldier]

Reloads?

Not to my knowledge, but I'm not certain.

 

[papersoldier]

Very high pucker factor right there

Very true. I felt a lot of debris hit my legs (fired from standing) so for a few moments before I checked myself I was a bit worried. Turned out to just be the rounds from the magazine that blew out.

 

[papersoldier]

That looks like it fired out of battery…. Yeah?

Definitely. Still not sure how or why it happened. It wasn't the first round out of the gun, and it was firing normally all day before then.

 

[Knobgoblin]

No firing pin issue?

 

[kmk1012]

Glad you are ok, but WTF happened?

 

[papersoldier]

No firing pin issue?

I left after that incident so I didn't inspect the rifle, but I'm sure my friend is likely diagnosing it at home as we speak.

I'm pretty confused as to how this happened even with a broken / stuck firing pin though (which seems most likely) since then I'd just assume it would slam fire, instead of detonating out of battery as it obviously did.

 

[papersoldier]

Glad you are ok, but WTF happened?

It was definitely an out of battery detonation, but no news on what actually caused it yet.

 

[Tlock]

Scary deal! Years ago I had a suppressor blow up on the end of a 22 mag and that was a hell of a boom. Glad you guys are ok

 

[kmk1012]

It was definitely an out of battery detonation, but now news on what actually caused it yet.

Keep us posted, maybe save someone else! Buy a lotto ticket!

 

[msgriff]

Headspace fail.

 

[P7M13]

Agree with @msgriff -- headspace fail. Not just raw bolt against barrel, but also chamber/case, as I describe below.
This can cause a firing out of battery.
If his AR10 chamber was tight, and the case head just a little bit oversized, you won't chamber by as much as 5mil, but the hammer will still hit the pin with enough angle to set off the primer. Kaboom.
Back it off a little farther, and the hammer will hit the firing pin at enough of an angle where it moves it forward and may slightly dimple the primer, but not ignite the round.
How do I know this? First hand experience....
My bolt would only close 2/3 of the proper rotation, locking the bolt in place but just barely. The hammer would strike but no fire (thankfully). I saw weak dimples and was relieved that it had not sparked off the round.
Took it home to examine the problem, where I discovered the fine discrepancy in diameters.
I solved my problem with a small base die.

FWIW, have the headspace checked now. Curts on McGloughlin or ORW in Tigard. Any time you have a catastrophic failure like that, you can wowie the chamber or damage the bolt.

 

[papersoldier]

Agree with @msgriff -- headspace fail. Not just raw bolt against barrel, but also chamber/case, as I describe below.
This can cause a firing out of battery.
If his AR10 chamber was tight, and the case head just a little bit oversized, you won't chamber by as much as 5mil, but the hammer will still hit the pin with enough angle to set off the primer. Kaboom.
Back it off a little farther, and the hammer will hit the firing pin at enough of an angle where it moves it forward and may slightly dimple the primer, but not ignite the round.
How do I know this? First hand experience....
My bolt would only close 2/3 of the proper rotation, locking the bolt in place but just barely. The hammer would strike but no fire (thankfully). I saw weak dimples and was relieved that it had not sparked off the round.
Took it home to examine the problem, where I discovered the fine discrepancy in diameters.
I solved my problem with a small base die.

FWIW, have the headspace checked now. Curts on McGloughlin or ORW in Tigard. Any time you have a catastrophic failure like that, you can wowie the chamber or damage the bolt.

This is very good info. I'll relay this to the rifle's owner. Thanks for your input!

 

[ma96782]

And yet.....some choose to laugh at a PSA (already built AR10 rifle).

Aloha, Mark

 

[arakboss]

Agree with @msgriff -- headspace fail. Not just raw bolt against barrel, but also chamber/case, as I describe below.
This can cause a firing out of battery.
If his AR10 chamber was tight, and the case head just a little bit oversized, you won't chamber by as much as 5mil, but the hammer will still hit the pin with enough angle to set off the primer. Kaboom.
Back it off a little farther, and the hammer will hit the firing pin at enough of an angle where it moves it forward and may slightly dimple the primer, but not ignite the round.
How do I know this? First hand experience....
My bolt would only close 2/3 of the proper rotation, locking the bolt in place but just barely. The hammer would strike but no fire (thankfully). I saw weak dimples and was relieved that it had not sparked off the round.
Took it home to examine the problem, where I discovered the fine discrepancy in diameters.
I solved my problem with a small base die.

FWIW, have the headspace checked now. Curts on McGloughlin or ORW in Tigard. Any time you have a catastrophic failure like that, you can wowie the chamber or damage the bolt.

@kmk1012 you might want to reconsider running the extended length firing pin in your 50 if you having any doubt about the lugs completely locking. I wouldn't want this to happen in your set up.

 

[Savage Jav]

Might wanna grab your calls and make sure the boys are still attached too