500JRH trimmed brass cracked case head

[rug480]

Any ideas to what may be causing case heads to crack? I know of split necks and stretching but haven't seen this before. 

Trimmed brass for 500jrh bfr. Not all of them, just a few are showing cracked lines on the rims. Only thing I can think of is maybe too much or long a bath with lemishine. I recall a few pieces of brass measured 1.41-415, but haven't checked if the cracked brass are the long ones. 

The Hornady on the very bottom right side shows the most prominent crack, was loaded with 15gr hs-6, 440gr plain base, cci300. 

Posted on castboolits FB forum as well, will do some more digging but would welcome thoughts from you all as well. 

Obviously the cracked brass will be canned, just haven't found anything on case head/rims doing this.

[squigz]

Can you post a picture of just the specific case you mentioned? I'm having a hard time getting a good defined image of the one you're mentioning out of the lot of them.

[rug480]

zoomed a little, case head thrust? 
I'll try to add some pics of the bfr cylinder and inside of frame later tonight. 

[bigbrowndog]

I don’t see cracked case heads, Blems or deformations, sure, but no cracks???
As well as a wide variety of primer conditions???
Trapr

[squigz]

I'm not seeing much of an issue at least from my point of view. As piece of mind I would just rotate those casings out of loading and keep an eye on other casings.