Oversize flash hole/case rupture

[Dave Marshall]

Or maybe make a cast of the chamber?

The throat is already shot out. No big deal to sacrifice it for science. The barrel was rechambered with a slightly larger reamer for testing purposes. The shoulder was pushed ahead a couple thousandths. The reamer should have cut the neck forward as well though. It’s why I am suspecting the case mouth might be into a carbon ring. The case mouth of the fired cases is smaller than a loaded round.

 

[Texas10]

YIKES!

 

[Uncle Ed]

I had a brand new 6xc case fail where the rim meets the body. It ruptured completely and did some damage to the rifle and shooter. This is also the only unsupported area of the chamber. I was able to find most of the debris and all of the ruptured case. The flash hole is considerably oversized and oblong in shape. So far, the flash hole is the only thing I can see that is not normal.

Was the flash hole oversized and oblong before firing or was it distorted due to the mishap.

 

[243winxb]

The case mouth of the fired cases is smaller than a loaded round.

Pinched neck = High Pressure. So it would seem.

OP photo, from below.

 

[Dave Marshall]

Was the flash hole oversized and oblong before firing or was it distorted due to the mishap.

It was most likely due to the over pressure.

However, even if it was manufactured oversized, according to the Army testing it would not have been a problem at all.

 

[rwj]

The case mouth of the fired cases is smaller than a loaded round.

Did you recall the bolt being hard to close when the rounds were chambered?

 

[Dave Marshall]

Did you recall the bolt being hard to close when the rounds were chambered?

Easy bolt close. First round extracted easily.

 

[Sniper338]

Im ready to see pictures. Im curious as for learning knowledge.

 

[GotRDid]

google patents search http://www.google.com/patents/EP2552619B1?cl=en Not saying this is/was the problem.

Brass - drawing vs extrusion. The extrusion of brass may not be the SAFEST METHOD of making brass. The cartridge case is manufactured according to the method of the invention as defined in the claim from a conventional seamed or seamless pipe, from which the final shape of a tubular section B is formed with cold forming of the pipe. Then a bottom C of the case, which had been produced by cutting, is joined with the formed pipe section B in various ways like welding, soldering, forming, pressing, etc. in order to manufacture a cartridge case. Figure 5 cartridge case in cross-section manufactured according to the method of the invention before and after placement of the bottom C of the case to the deformed pipe B. New patent 2010.

Very interesting; but I certainly would not knowingly purchase or use brass/ammunition assembled in such a manner.
Thank You, Sir.
GotRDid.

 

[Ccrider]

Note to self, start wearing shooting glasses---all the time. No exceptions.

Thanks

 

[Bc'z]

Ditto.
As far as prescription glasses looking through scope.
Use my readers or my distance pair

 

[Pwc]

Section the blown brass.....

 

[fyrewall]

sounds like defective brass, recover any brass pieces and try to reconstruct - look at everything.

 

[Dave Marshall]

 

[Bc'z]

WOW!!
Glad your good n didnt loose that eye or worse.

 

[Bill K]

I had a catastrophic case failure. Trying to figure out why.[/QUOTE]

Are you sure that round did not have a over charge or powder somehow ? It just sounds like high pressure from such, rather than just a enlarged flash hole.

 

[Dave Marshall]

I had a catastrophic case failure. Trying to figure out why.

Are you sure that round did not have a over charge or powder somehow ? It just sounds like high pressure from such, rather than just a enlarged flash hole.[/QUOTE]

I agree. Probably not the flash hole.

Even a full case of powder shouldn’t rupture. I only own medium rifle powder. A full case of any of them shouldn’t rupture.

 

[Pwc]

Flash hole deformation sounds like the result of thebrass failure rather than the cause. Given the stated facts, sounds like the unsupportrd head let go either from bad brass or over charge

 

[Albany Mountain]

Wouldn't the enlarged flash hole be a RESULT of the overpressure? I had one this fall and came to that conclusion.

 

[mrjdasr]

I was incredibly lucky. I have a bad habit of shooting without glasses. It's obviously not wise. The case ruptured and vented gases out the magazine well and along both sides of the bolt. The magazine was blown out and the bottom metal deformed. The extractor (sako style) was blown off and hit my cheek. The bolt catch was also blown off. I was hit with shrapnel on my cheek and just above my right eye. My eye was amazingly unharmed. INCREDIBLY lucky. It's a huge lesson for me and I hope others as well.

The rifle is not new. I had an older barrel with a smaller chamber re-chambered with a larger reamer. I fired one round with no issue and the following round blew up the rifle. I have fired over 100 pieces of the same brass without issue. The first fired case measures as expected. There were no obvious issues with chamber dimensions in the fired case.

explain the procedure to rechamber with a larger reamer and still have a carbon ring
or was it the same reamer run in a little deeper. if that was the case, a carbon ring could still be there