What could cause these circumferential cracks?

[quack1]

http://i291.photobucket.com/albums/ll300/1quack1/IMG_0096.jpg (http://s291.photobucket.com/user/1quack1/media/IMG_0096.jpg.html)
Never had this happen in nearly 50 years of loading. Bought new, 32-20 caliber, twice fired, only used with mild cast loads. After finding these, I checked inside of the shoulder of the remaining brass with a bent piece of wire and found 9 more that were starting to crack. That's 15 total out of 100 pieces of brass I started with. Have used other brass in this gun with no problems.
I have a guess as to what might have caused this, but would like to hear other possibilities.

[Sensai]

Are you loading with black powder? I have seen an air gap with a BP load do this. That was in a 32-20 also.

[Gtek]

That sign would be enough for me to anneal survivors. I have used the propane, socket on battery drill dropping in water bucket. Too easy once you get the set up. Cracking on shoulder on every one? Just because it came shiny new does not mean it is where it needs to be. Gtek

[John Allen]

It looks like hard brass to me try annealing it. I have had this happen with 22 hornet brass.

[Larry Gibson]

If you are not using a filler such as COW(what load, what firearm?) then I suspect you are FL sizing the cases with the shell holder bumping or just short of the bottom of the FL die. If that is what you are doing then you are setting the shoulder back way to far for the chamber. Back the FL die off so the shoulder is just slightly bumped (partial sizing).

Annealing and adjusting the FL die as above may save the cases for a few more firings but it's hard to say.

Larry Gibson

[quack1]

Are you loading with black powder? I have seen an air gap with a BP load do this. That was in a 32-20 also.

Smokless powder.

[quack1]

[QUOTE=Larry Gibson;2403134]If you are not using a filler such as COW(what load, what firearm?) then I suspect you are FL sizing the cases with the shell holder bumping or just short of the bottom of the FL die. If that is what you are doing then you are setting the shoulder back way to far for the chamber. Back the FL die off so the shoulder is just slightly bumped (partial sizing).

Annealing and adjusting the FL die as above may save the cases for a few more firings but it's hard to say.

No filler, 5.2gr Unique, 1400 fps., Lyman 3118, Winchester M-53. Not set up to full length size. First thing I checked after I saw the cracks, thought maybe the lock ring on the die was loose. The fired cases go through the sizer with very little resistance.

[montana_charlie]

Bought new, 32-20 caliber, twice fired, only used with mild cast loads.
How does the thickness of the rim on those damaged cases compare with the depth of the rim cut in your chamber?

CM

[MtGun44]

Minimize your sizing - you are probably pushing the shoulder back too much and over
working the brass when it fires. Try for just barely sizing deep enough to hold the
boolit.

Bill

[quack1]

Thanks for the input.
In the original post I said I had a guess as to what caused the cracks- I'm in agreement with those of you that said the brass was too hard and needed annealed. I wouldn't normally expect to need to anneal new brass, or brass that has only been fired twice, though. I do commonly anneal necks after 4 or 5 firings for brass longevity and maintaining reasonably consistent neck tension. I have never used this brand of brass before. I'm purposely not saying the brand of brass as I have emailed them an inquiry and, so far, have not received an answer.
For those who said I might be setting the shoulder back too much, I checked the sizing die by smoking the shoulder of a fired case and sizing it. The soot was barely touched by the die. And, if I had been setting the shoulder back, I would have expected head separations, rather than shoulder separations. The brass is not getting sized very much, it runs in and out of the die very easily, and I made my own neck expander die to give me between .001 and .002" neck tension on the bullet. I have been only crimping enough to remove the slight bell at the mouth.
I will add to this thread when I hear from the manufacturer.

[MtGun44]

Good additional info, so it makes it more of a puzzle to me. Brass cracks from
excessive hardening and hardening only comes from permanent deformation -
"work hardening", like sizing. So, if it is not being worked too much, then it
must have been too hard to begin with - so annealing should help.

Bill