AG Composite and Peak 44 could be worth a look.
AG Composite say they have 15 in stock for a Magnum action (9 lug), #2 barrel (too round of a number not to be at least a little suspect???)
It's our goal to deliver the highest quality composite rifle stocks available at competitive prices with lead times measured in weeks not months.
agcomposites.com
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Peak 44 makes a super super lightweight stock. They're making stocks for some of the factory Weatherby options.
No mention of lead time or inventory. You mentioned 340 Weatherby and recoil, so maybe super lightweight isn't a exactly what you need. I assume no brake?
Peak 44 builds ultra lightweight technical gear for outdoor professionals
peakfortyfour.com
I just happened to be researching stocks for Weatherby's over the weekend. A couple of years ago, McMillan's offerings were slim to none but they're under new ownership, so...