Strange case failure

[Doug Beach]

At a recent match, another shooter had a Lapua 6br case completely separate at the neck/ shoulder junction, leaving the neck in the chamber. The point of separation looked quite clean, not jagged. The case had been fired 7-8 times, and was not neck turned. Other fired cases from the same batch of brass, same load, looked completely normal. The barrel / chamber has several hundred rounds through it, with no previous issues. As far as I know, the cases have not been annealed.
Is this most likely a brass defect issue, or is there a reloading error that could have contributed? I don’t know all the details of his loading process.

 

[M-61]

I don’t know all the details of his loading process

That presents a problem

 

[Thud]

It's happened many times before not unusual.

 

[M-61]

It's happened many times before not unusual.

To him?

 

[Rocketvapor]

Is this one of those 'Neck Size Only' cases?
No bump.
7 or 8 times without annealing?
Where would you expect the case to fail?

 

[Doug Beach]

I’ve never annealed, and I’ve never had any kind of case neck failure, with cases reloaded well past 10 times.
I’ve been reloading for over 30 years, with 10’s of thousands of rounds fired in competition, and I’ve never seen this particular failure, in my brass, or anyone else’s. Just peaked my curiosity, is all.

 

[Rocketvapor]

We'll probably never have the answer.
Exactly what bushing/mandrel did he use?

 

[Doug Beach]

We'll probably never have the answer.
Exactly what bushing/mandrel did he use?

I’ll see what I can find out.

 

[243winxb]

The point of separation looked quite clean, not jagged

Neck turned?

 

[Doug Beach]

Neck turned?

No.

 

[Doug Beach]

For all previous firings, he had used an SAC bushing die, with a .267 bushing. For this time around, he used a standard factory Forster die, non bushing. We might be closing in on it…

 

[K22]

Without detailed information and maybe even with it, any diagnosis might be just supposition.

However, given the failure mood, I will take a stab at it, if the case was annealed, I would suspect over annealing causing the brass to exceed its elastic limit.

 

[old codger]

My bet is just a case of work hardened brass.

 

[bugman]

For all previous firings, he had used an SAC bushing die, with a .267 bushing. For this time around, he used a standard factory Forster die, non bushing. We might be closing in on it…

A standard non-bushing forster sizer will squeeze that neck to 0.261-0.262, and that is quite a leap from 0.267. That same no turn neck is then blown out .010+ upon ignition. Also, that non bushing sizer sizes the entire neck length, all the way to the shoulder.....contrast that with a .267 bushing with a bevel that usually sizes only part of the neck.
The end result is quite a "crease" at the neck-shoulder junction, and that will be a weakened area for unannealed and multiple-fired cases.
I have no idea why other cases didn't separate, but suspect that will occur in the next firing or two if nothing is changed

 

[gunsandgunsmithing]

No.

That's what gets me. I've been guilty as well as seeing others do the same thing, neck turning a bit too far into the shoulder and it will happen but I've never seen it, that I can recall, with brass that was not neck turned. Fairly common mistake from people new to neck turning brass though.

 

[243winxb]

used a standard factory Forster die,

The bushing allows the unsized neck area to fully expand to the chamber.
The Foester sized that area down maybe .015" Then opened back up again, with some type of expander. Brittle brass?

quite clean, not jagged.

Could be where the bushing stopped sizing?

Just guessing.

My 223 brass, were never a clean break.

 

[Doug Beach]

I haven’t seen the neck portion, it was still stuck in his chamber when he left. The break in the case body was pretty clean. I think we’ve figured it out. Thanks everyone!

 

[M-61]

Neck turned?

From the OP:
“….and was not neck turned.”

 

[coldboreshot]

Still too many variables without detailed info.

 

[Kracken McGraw]

While we’re on the subject, what size brush would you use to fish that 6 neck out with?