I've learned a lot from my 25 basic, 25-25 posts.  I'm wondering if maybe when I get moved and settled I should consider turning my own straight wall 257 Cal brass?  It would be a great way to get my feet wet on using the lath.  I'm open to any input regarding case design.  I want to be able to load black powder at aprox. 1100-1200 fps for small game hunting.

You could turn some.25-21 cases, on the "Everlasting" pattern, with the outside to fit the chamber, the case mouth to fit the bullet and slightly thicker than normal sidewalls so you only need to decap, recap and reload.

This is the way to go with turned cases.  They do not stand up to resizing like drawn cases do.

A lathe with collets would be the way to go for a job like this.  It would be a little tedious and finicky, but five or ten cases should last a good long time.