I own both 500 NE Doubles and an Origianal 505 Gibbs and have hunted DG with both.

A 500 NE Double such as Ray Atkinson et al suggest (Searcy) is probably the only option
in your price range. I can't comment on Searcy's as I've not seen / used one but Ray and others
recommendation is good enough for me.

505 Gibbs Brass and Dies etc are more expensive but it is a GREAT Calibre.

Actions - Genuine Magnum Mauser 20 actions are probably too expensive now
but I see plenty of good copies around.

The alternative is to use a Brno 602 or 550 action as this is Big enough.

Personally, I would go for a double 500 Nitro.

Hope this helps

500 Nitro