About all magnum cartridges call for some amount of freebore. Speed ain't free. I see the 300RUM calls for .1-.2", the 7mmSTW about the same. The weatherby's call for well over.3-.5". The winmag is about the least. My winmag has .05 of freebore if loaded to max SAAMI specs.
If you ever make the mistake of having a custom rifle built and having the gunsmith ream with no freebore, you can count on not being able to shoot factory ammo.