[Unclenick]

Jcwit,

It's dust and other hard grit on the brass that eventually wears them out.


OEF-vet,

Most of the low pressure straight pistol cases don't grow with firing the way a rifle case does. My .45 Auto brass actually shortens about half a thousandth per load cycle.


Wallyl,

I've seen brass work harden and get springy at the mouth so that even a good sizing die no longer squeezes it small enough to overcome the spring-back. This is case brand dependent. Remington .45 Auto brass in my old Lyman carbide die did this. After two or three load cycles, bullets would start falling into the resized cases.

If your .357 brass isn't doing this, then it's not the die, it's the brass. All I can suggest, if you want to keep using that brass, is you get a narrower die. The Dillon dies are usually fairly snug. They usually make the Remington .45 Auto brass work that my old Lyman die would not, but I would call and ask what size their carbide sizing ring ID is before buying. Measure the ID of yours with a small hole gauge or run a pure lead slug through and use a micrometer to find out what size it is to compare. You are likely just looking for a thousandth or two narrower.