I love to know the evolution of that law. Why .25 or smaller? seems like the lawmakers don't really want you to hunt.
As a 25-20 owner I vote for .256. There is only one jacketed bullet you can use and cast - no, not for me. Necking down 32-20 to 25-20 is not as forgiving as it seems.
you can buy .218 ammo, brass and bullets consider that one.