cracked case necks?

[Marco Califo]

Scatter, what brand of brass was that?
OIC Winchester.

 

[Shadow9mm]

Recently I was in the process of loading some NEW Winchester brass 300 Mag ammo for a friend and was having trouble getting the tolerance which I like. I annealed some of the cases and resized them to see if they would react better. What I found in some of the brass was a crack, just from sizing, that appears just as your case looks. Inspecting it with a punch I found that the brass was in two layers and they could be separated.
Have you pulled the bullet?

not yet. will be next week some time before I can get back to the bench to pull it.

 

[stagpanther]

Recently I was in the process of loading some NEW Winchester brass 300 Mag ammo for a friend and was having trouble getting the tolerance which I like. I annealed some of the cases and resized them to see if they would react better. What I found in some of the brass was a crack, just from sizing, that appears just as your case looks. Inspecting it with a punch I found that the brass was in two layers and they could be separated.
Have you pulled the bullet?

I use lots of Winnie brass--not because I like but because it was some of the only stuff I could find. My Winnie 44 mag cases seem to last forever--but in some bottleneck cartridges the cases can be suspect. In particular, the turning (or whatever it is they do when they make them) often has vertical chatter in the ID of the case neck, so I generally will run them through the sizer a couple of times (just enough to get the expander past the shoulder) even when brand new to smooth that down. I end up sometimes having to work the necks in the same way I would if I were necking down from a bigger caliber.

 

[scatterbrain]

I'm not bad mouthing Winchester's brass, just reporting what I encountered. This was new unloaded brass that was purchased when you were lucky to get anything. I have had no other trouble with Winchester and I use it a lot.
At that time I purchased a couple of boxes of loaded PMC in 300 Win Mag just to get the brass, and to my delight I am still using the brass. Probably 7 times recycled, but I do anneal it every time.
The split Winchester brass appeared to have sheared into two layers in the neck when sized down to the .308 size. I could pick it apart into two layers, and the first noticed crack looked just like the above photo, hence the comments.

 

[stagpanther]

Most of the bigger Winnie brass I get in bottleneck cartridges usually needs at least some neck work. A necessary evil to having otherwise unobtainable brass.

 

[MarkCO]

That is not a typical split. It could be just a bad case from the manufacturer, or, if wet tumbled, one that had stress corrosion cracking from too high of a temp/acid level. Possible too that the bullet itself was oversized or had some aberration protruding, but still and odd split from that.

 

[Unclenick]

Yep. It's wierd. The extrusion forming process should leave vertical toolmarks and cracks usually follow those. The two-layer effect mentioned by Scatterbrain is something I've seen in heads formed from cups that were formed from punched discs of brass rather than by the slug extrusion method. The heads forming was either not formed with enough force or they were formed with surface contamination. But two brass layers at the mouth? I don't know how they managed that unless the cup mouths folded over during extrusion and the forming lube kept the layers separated.

These days the big brand names outsource so much work, the fault may never be placed.