Re: WTB 340 weatherby brass.
I don't have any brass. If you're an experienced handloader, you could try this.
When I shot this round I bought Remington 300 Weatherby brass and using Hornady 340 WM dies, (tapered expander ball standard) ran them through the resizing die thus expanding the neck to .338.
Check overall case length, and work up a load watching for signs of excessive pressure. The Remington brass may be a little softer don't know for sure.
Remington 300 WBY Brass is much more economical $ wise, and easy to find.
If you already have another brand of die you can probably order a tapered expander ball from the manufactuer. I know you can do this for RCBS dies.