Your own reloads. You're never going to get a whole lot better shooting factory ammo. You have no control over case-to-chamber fit or bullet-to-rifling distance. You can reload for $150 or less and start making better ammo for your rifle. I have used Lee's little Reloading Press (~$35) for loading .30-06. It's not as nice as a more expensive press, but the ammo what just as good.
IF there is a factory round using a Sierra Matchkings, that is probably as good as you'll find.