Factory .25-35 brass splitting

[raymill]

I picked up a 1907 Winchester in .25-35 today with 6 boxes of factory ammo, probably manufactured in the 60s. I loaded some up and ran about a dozen rounds to check for function with no issues. when picking up brass I noticed 5 casings had multiple splits After that I decided not to press my luck by firing anymore. What would cause this, ammo to old or what.

Thanks

The ammo was Winchester super speed, Remington Kleenbore, Peters high velocity

[Zombie Steve]

Lengthwise splits or around the case head? If the case head looks to be separating, that's almost always a headspace issue. Were the splits happening in one kind of ammo, or with all three kinds? It's doubtful it's the ammo if it happened with more than one kind. Pictures might help.