Can anyone tell me what happens to the overall length of a piece of brass when sized down quite substantially?

Example: Take a 357 Maximum brass - 1.605 inches - and size it down to 25 caliber? Does it stay the same length, grow longer or get shorter?

Thinking about creating a 25-222 Rem a.k.a. 25 Copperhead but use 357 Maximum brass because of the rim. The 25 Copperhead brass has an length of 1.660.

generally speaking the neck will be long and need to be trimmed.

It will get longer as you size it down, but, I wouldn't expect it to grow .060", more like .020-.030" The other thing is it won't lengthen consistantly from case to case, and you'll have to trim to the length of the shortest case.

"The more it's squoze, the more it grows...."