Curious neck/shoulder case rupture.

[P7M13]

338 Win Mag, Winchester M70
Nosler 250gr E-Tip bullets.
Vhitavhouri N165 Powder
Doing a load work-up from 62-75gr to find nodes.
Starting at 62gr
Cases were full length sized
Zero other pressure signs.
Q: What are potential causes?

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[ar addict]

My guess would be poorly annealed.

 

[Xmark1]

That is work hardened brass.
Usually, the neck will split first.
Since its the shoulder, I second the previous post about poor annealing.

When I anneal, I heat up the neck but also make sure the shoulder gets hot also.
Also, after fireforming, I only neck size, until the next anneal.

 

[bionic knees]

I don't anneal so when loading I clean and carefully inspect each case for any sign of problems, seems like about 4 reloads and I start seeing problems on some calibers, 5 or 6 and they are ready to be recycled.

 

[P7M13]

Yeah, thought possibly annealing. These were not, though it was only their 2nd firing.

 

[Xmark1]

Yeah, thought possibly annealing. These were not, though it was only their 2nd firi

What headstamp?
After a closer look at the picture. The junction between the shoulder and the case sure looks rounded.

 

[P7M13]

Federal

 

[ar addict]

We had a barrel of FC 15 5.56 brass that had case head separation.
This was once fired brass, sent it to scrap.

 

[Xmark1]

Federal

I have shot thousands of federal and have never seen a case split like in the picture.

 

[P7M13]

My only other concern was that this being loaded nine grains below the Nosler site charge range, that I may have had a quasi-detonation. Recoil didn't indicate that. Nor any other case markings.

I have shot thousands of federal and have never seen a case split like in the picture.

Have found many dozens of 223 at the range, brand new, with their necks split.
Also, pull, anneal, reload and fire -- easy way to test the annealing theory. Had 100% failure rate this evening....

 

[Xmark1]

My only other concern was that this being loaded nine grains below the Nosler site charge range, that I may have had a quasi-detonation. Recoil didn't indicate that. Nor any other case markings.

Have found many dozens of 223 at the range, brand new, with their necks split.
Also, pull, anneal, reload and fire -- easy way to test the annealing theory. Had 100% failure rate this evening....

I'm not fond of federal brass. The necks start to split after 4 or 5 reloads. But Yikes! never seen it with new brass.

 

[ar addict]

Have found many dozens of 223 at the range, brand new, with their necks split.

With all the home built AR's, I think headspace could be a problem.

 

[Local Loader]

So was this once fired by you or were they pickups or bought or factory?

 

[Xmark1]

With all the home built AR's, I think headspace could be a problem.

That was my first thought.

 

[Xmark1]

338 Win Mag, Winchester M70
Nosler 250gr E-Tip bullets.
Vhitavhouri N165 Powder
Doing a load work-up from 62-75gr to find nodes.
Starting at 62gr
Cases were full length sized
Zero other pressure signs.
Q: What are potential causes?
View attachment 1088304

The broken off neck is dirty. You polished the other pieces. That makes the detective work more difficult.

 

[Local Loader]

What does the inside look like and I noticed that the neck and shoulders are not the same length, if they are all 223.

 

[bcp]

I hope the different lengths are because you laid them flat, not standing up, for the photo.

Bruce

 

[P7M13]

So was this once fired by you or were they pickups or bought or factory?

Fired by me or the prior owner. Bought rifle with 3 full new boxes and ~100pcs of brass ages ago.

What does the inside look like and I noticed that the neck and shoulders are not the same length, if they are all 223.

Optical illusion. They are all the same length. These are 338 Win Mag. The Federal range brass with split necks that I was talking about was 223.
Inside what I would deem clean burn, normal powder residue. The outside of the cases looked like hell from gas leakage, so I rubbed them with steel wool. Doubt any of these got a good seal, though there was no soot in my face on firing.

I hope the different lengths are because you laid them flat, not standing up, for the photo.

Good call. I stood them up and put a steel ruler across the top. All the same length - i.e. of the three, I did not see any light between the ruler and the case mouth.

With all the home built AR's, I think headspace could be a problem.

Would agree, but the split necks I was talking about were all longitudinal splits - which would be a throat diameter problem.

 

[drstrangelove]

As mentioned above, those shoulders don't match up… if they are aligned vertically, you are getting inconsistent full length resizing, and setting the shoulders too far down for your chamber. The shiny neck band on the right is evidence of excess brass stretch. Fire forming on annealed brass will stretch to a degree. With non annealed brass, it will fracture.

Buy new brass, anneal after every firing, and press the shoulders down in thousandths until you can JUST get the bolt to close with minimal resistance. Crank the Allen set screw on the die down right there. You will need to remove the expander ball/deprimer when setting the shoulder height or the neck won't chamber since it's expanded. .

That way you aren't beating the krap out of every case you are shooting.

 

[P7M13]

As mentioned above, those shoulders don't match up… if they are aligned vertically, you are getting inconsistent full length resizing, and setting the shoulders too far down for your chamber. The shiny neck band on the right is evidence of excess brass stretch.

Haven't pulled out my headspace checker to verify the exact shoulder position, but standing the cases up, all are the same length, and all shoulders at neck and body align. That was a D'oh photograph, and as commented on by @Xmark1, screwed up the analysis by rubbing the cases with steel wool.

I think the band you may be talking about are the bite marks from my bullet extractor - seems I seated a bullet too deep and went to pull it out to reseat, but grabbed the case neck first. Nowadays, if I do that, I'll toss the case into my scrap pile.

In all my 7 rem mag and 338 Win Mag reloading, never bumped shoulders, always did the lazy "full size". Guess I'll start doing that on the 338.