savage458 - Have you considered a Triple 4? Yeah - I know the case is a littler short, but it should work perfectly. With a fast twist .429" or .430" barrel, say 18" twist, it will be VERY accurate with 340gr. bullets at about 2,300fps - maybe more if a suitable powder can be found. As well, it should do about 2,400fps with 300's and 320's.
Just a thought.