Can this be done by just passing straight through a .308 die or does it require several intermediate steps?

Should take just one pass, using a tapered expander. But then again, why waste time when there is so much 308 brass.

I would find someone that needs your 243 brass and try making a trade for the 308. No fire forming required.

HBL

...You are right, but I have a friend who is bugging me for some nickel cases in .308.

I have some in .243 and thought I'd play around with them, just to be nice.

The require resizing, fireform, then resize again, right?

Been there, done that.

Necks end up too thin and split or won't hold bullet tightly enough.
Just like when you neck .308's down to .243, the necks end up too thick and need to be turned or they won't fit the chamber.

It does work and doesn't thin as much as you would think. The biggest problem is that in passing an expander into the neck, the neck expands eccentrically at the path of least resistance. It's not likely the the necks of the 308 would be centered in the shoulder and would be lopsided. They would require fire forming before they are useable for any kind of accuracy. You would end up with very marginal brass because of it, plus all the other points mentioned by others. If you want to be nice just buy the guy some 308 brass.

I know, it's just that it's hard to come by here.

I'll check out some of the possibilites people suggested on another thread.

Thanks all.

I understand what you are saying about being hard to come by, I didn't notice where you were located, but now I see.

Good luck, you can try it, but be ready to use a lot of brass.

HBL