Still have the belted magnum and standard actions. The Rigby actions are sold out.

If I understand the final sentence correctly, the larger unmodified actions have all been sold, is that correct?

The actions that CZ called the "Rigby" have been sold. They had a bolt face sized for the 416 Rigby and a minor difference from the "belted magnum" action in the shape of the magazine well under the rails, and the extractor claw. The "belted magnum" action is otherwise the same as the Rigby in size and shape. It was used for the 375 H&H, 458 win and Lott, 404 Jeffery, 416 Remington, et al. It can be opened up to accept the Rigby sized cases and larger. I've done it plenty of times.