Target accurate varmint rifle:
To guarantee this its about gotta be a at least a semi custom. That is trued action and fitted high quality barrell plus a really decent bedding job.
Action would be savage or rem.
Barrel would be up a grade from douglas say a Lilja.
Cartridge could be a couple of choices:
Top of the list would be 6mmBR or 6mm Dasher and shoot the 107gr bullets. Dirt cheap to shoot once set up and good to twice 500 yds.
Second choice and probably way more exciting would be something like a 22 243 Ackley Improved. Then shoot the Wildcat 100 gr bullet at about 3200. Also good to twice 500 yds. Built properly it'll be competition accurate. Need at least a 7" twist though.
I'm using a 338 Win for fairly long range yotes this winter. Expect it to be a bit much, even more than a 300 Win but what the heck, its accurate enough and I can shoot it well enough

but for yoting one of the above will replace it one of these days or maybe even a bigger case.