Is it strictly for punching targets or is there going to be some hunting involved? Do you reload your own ammo?
If its strictly paper punching gun then a .223 with 1-8/9" twist would be your choice for being most economical and with large availablity of precision ammo. Rifles as Savage (10FP), Remington 700p (Tactical/VTR), Tikka Varmint/Tactical will work well up to 600yds with proper bullets/ammo choices.
If its going to serve as deer/bear and target gun then .308 would be by far best choice, same rifles above can be had with fast twist to handle heavier, longer, target bullets. There is plenty of choices for ammo and accurate rifles.
Scope choices will depend on your budget, and again if its going to be used for hunting or just target shooting. Simply too many choices and possiblities.