Off the shelf help

[overinfinite]

Savage Precision or Ruger Precision for factory chassis rifles
Springfield waypoint, Bergara HMR, Browning X Bolt or Xbolt2 for factory stocks the brownings have flimsyness though. Also, the standard 307's seem like they have quite a bit of flex in the stock, fine for a bipod though.
I started this journey with a Ruger predator in 6.5CM over a decade ago and have built it in 5 different configurations since owning and have lent that thing out to so many people with different stocks/ chassis'. Shoots in the .7-.9 consistently with any berger or nosler bullet.

 

[JAYgs8163]

Go for the Weatherby and you should be good with factory ammo offerings on the 7PRC. I'd consider the 65 PRC as well for lighter recoiling if he's a novice but you could run the 7PRC with lighter projectiles if available to keep recoil down. Both have good support of factory ammo. 500 is pretty easy to attain with a good amount of practice by the shooter and the understanding of using it in the field wisely. There are so many well made factory rifles now you should have multiple offerings to look at. Without knowing his game animal desire to hunt the question is a little open ended to choices.

 

[CMRHG]

I've put together a handful of Tikka T3 Lite 300WM. Shooting hornady 180 gr SST ammo around 3100 fps, all 1/2 moa. Burris Fullfield 3x12x56. They kick so I put Witt machine clamp on muzzle brakes on them. Nice lightweight 500 yd rigs for about $1700

 

[skipglo]

For just a Fun gun and some hunting why not just a Vanguard or Howa....sub moa guarantees on both....save him a pile of money and get him where he wants to be.... anything more and he wouldn't be able to appreciate the difference. I'm a big fan of both guns...drop it into an MDT FIELD STOCK .....just me