Rifles can sometimes be a mystery. I've seen Savage 110's outshoot high priced custom guns. I've looked at perfect barrels that produced terrible accuracy, and terribe looking barrels that shot MOA. Go figure, so I'm not gonna touch that one.
As for calibers the .308 win is an extremely versatile round. If you want a bit more performance, you can use Hornady's light Magnum rounds for a bit more punch. In addition, tactical ammo- such as the TAP is usually available in .223 and .308 calibers.
Good Shooting
RED