G'day Steve,

I have no experience with the Rigby but I do with the 416 Rem. I'd be tempted to load that Rigby down to 2500fps with woodleigh 410 softs and solids and put a soft on top of a mag full of solids.

With the other rifle I would take the 577 for your brother then you'll be there to act as back-up if things go apeshit !!

Cheers,
Mark.