Steve,

338 Lapua Tactical Rifle on a steady BiPod accurate out to
800 - 1000 metres. The just drop them.

No, you'll need something that goes minimum 300 metres accurately
(if not 400) so you can stop any hit ones from running - or you can run
/ drive after them !!!

300 WM, 300WSM, maybe something bigger but then you loose out on
flat trajectory.

Also remember if you end up walking it can be a long fast chase so you
may have to carry what you shoot.

Good hunting.

500 Nitro