Hit a bit of a stop on my necking up .416 to .510"

I have expander balls up to .457". That was no problem. I thought I had a .475" too. Still looking for it through over 100 boxes of dies!?

I've thought about just loading them up with cast 405 gr. .45/70 bullets and shooting into sand to form to straight wall .510". The "fire-form" using a resisting projectile seems lots more gentile than a violent "blank". Uses lots less powder too. These cases are super thick as well.

I might make me some "expanding mandrels" on my lathe to insert into some odd Lee expanding dies. It's not really made for that but it would be handy to use as a concentric holder, and easy to make mandrels to fit. I have to measure the ID of the die body too.