One of the reasons the Mauser barrels were stepped was to reduce the wandering POI effect of a barrel that had a wandering bore as it heated up.
Some Mauser barrels have quite a bit of wander. This is very noticable when a long barrel is shortened. The bore can be far from the center of the new muzzle.
In the old days barrels were straightened using a hand turned arbor, and Savage still uses the old method. This requires highly skilled craftsmen.
At some point it was decided that so long as the last six inches of the bore of a milspec barrel was straight it would be accurate enough for government work.
If you want the best barrel be willing to pay for it, and buy from a highly respected barrel maker.