Any other cause for split necks?

[Dr Prepper]

Just curious, is there any other common cause for split case necks besides being reused to many times?
Like is there a common issue in semi auto rifles?

I have some .308 brass (not sure where i got it from probably range pick ups) thats LC and LC "LR" some look in decent shape, some have terrible split necks. Straight down the neck about .25" Doesnt look cracked though, it looks scored or pinched and then the split occured. There is some light locking lug dents from extraction nothing too crazy. The other ones mixed in look fine.
Havent looked for rings inside yet, maybe tomorrow.

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[DizzyJ]

Overly generous sized chamber.

Brass not properly annealed from the beginning.

Necks too thin.

Loaded too hot.

Any combination of the above.

 

[Pepe-lepew]

Overly generous sized chamber.

Brass not properly annealed from the beginning.

Necks too thin.

Loaded too hot.

Any combination of the above.

I would add to your list dies that overly resize the neck causing the brass to overwork.

The scored or pinched look of the split is caused by necking (concentrated yielding) of the brass before fracture. Ductile material tend to neck before fracture.

 

[po18guy]

Might also have been tumbled/cleaned with Brasso or any other brass polish which contains ammonia. Exposure to ammonia causes embrittlement of the brass.