Curious case failure

[Bill Daniel]

I had a case rupture today. Star line 45-70 brass on forth reload. 350 grain Berry’s bullet over 40 grains IMR 4198. The rupture was mid case along the long axis. Was this a brass defect or?http://IMG_0945.HEIC.
Thanks,
All the best,
Bill

 

[BBarn]

Your photo/image doesn't show up for me.

The load seems mild and should be fine in anything modern (but not in a 1973 Springfield of course). It's possible that the brass is a little hard, making it more brittle. Or it could also be a bit thin. Both of those "defects" can lead to early case failures.

Another possibility is a significant difference between the sized diameter of a case versus the fired diameter of a case. The greater the difference between those two, the more the brass is worked during each reloading, leading to fewer reloads before the brass fails.

 

[Chainsaw.]

BBarn preety mich nailed it. You might consider anneling the rest.

 

[F. Guffey]

The rupture was mid case along the long axis.

Yeah he nailed it.

But there is a chance you did not measure the case before and again after firing. We do not know what effect the chamber had on the case when fired and then there is the diameter of the barrel when compared to the diameter of the bullet, I want my bullets to create enough pressure to seal the chamber between the chamber and case.

If your powder is too slow or the pressure is recused because the bullet is too small in diameter gas can get trapped between the case and chamber. When the pressure inside of the case falls the outside pressure can rupture the case. It is possible for the case to rupture and the case can collapse inward.

The 45/70 case has a tapper of about .020" from the case head in front of the rim to the mouth of the case. If the chamber is too large in diameter I suggest you back the die out to reduce the dies ability to size the case.

I do not know what a good number would be but most reloaders use fractional turns of the die; I don', I go straight for it. I use a feeler gage to adjust the die off of the shell holder, I like to start with .010".

There were times I went for the magic .002", and then there is my M1917, I go straight for .014" when sizing 280 Remington cases for that 30/06 chamber.

I do not know how other reloaders do it but it seems the fiddle with it until they get there.

F. Guffey

 

[Bill Daniel]

Thanks to all.
Sorry about the picture. I tried to follow the instructions but there was no photo/album to open to upload the picture. I believe the case is sealing well in the chamber as the outside of the cases are clean after firing. I have never annealed my brass before. Since it is mostly straight walled do I anneal all the way to the case head?
Thanks!
All the best,
Bill

 

[BBarn]

Since it is mostly straight walled do I anneal all the way to the case head?

NO! Just the top 1/4 or so. Periodic annealing can reduce splits at the mouth but I wouldn't expect it to help much in this instance. Assuming the lot of brass is OK, your best hope may lie with sizing the OD of the case a bit less (something that may not be easily accomplished).

 

[T. O'Heir]

Annealing isn't going to help a straight walled case. That's a case life extension technique for bottle necked cases. Work hardening of the neck and shoulder gets softened by heating with a propane torch until the brass changes colour. Red hot is too hot.
"...mid case along the long axis..." So a split lengthwise? Annealing will not help at all. That's simple metal fatigue. It might have to do with the load.

 

[Bill Daniel]

Thanks fellows. I’ll keep watch on the rest of the batch.
All the best,
Bill

 

[Jim Watson]

Annealing is very commonly practiced by BPCR shooters to make their straight cases seal better, give uniform light bullet pull, and last longer. Sorry again T.

The technical term for a case with body split is "worn out."
It might be due to wide diameter changes between sizing die and chamber and you could make your brass last better with partial sizing.
What gun?

 

[Bill Daniel]

Thanks Jim.
It’s a Henry H010 45-70. Standard Lee resizing die and as mentioned the fired cases are clean on the outside so I believe they seal the chamber well. Would it be useful to compare the pre fired to the post fired case diameter and if so where (mouth, mid body, head) to see if the chamber is too large in diameter?
Thanks.
All the best,
Bill

 

[Jim Watson]

I would. Not hard to do.
I don't know how partial you could get on sizing for a repeater, lots of Sharps shooters don't size at all, just clean the case and slip fit the bullet.

There is a good chance that was just a weak piece of brass and it simply didn't last. I wouldn't get too exercised about it unless you get more of the same.

 

[Bill Daniel]

All the best,
Bill