As others have shared the barrels are hammer forged. Hammer forging process.
A blank is clamped in a rotating holder. The rotation is not used to produce the rifling twist in a hammer-forged barrel; the twist is in the mandrel. Rotation is used to keep the barrel round during the forging operation. The mandrel is inserted into the borehole, and the barrel moves at a constant speed toward a series of cam-driven hammers arranged in a circle. Hammers are paired 180 degrees apart to equalize stresses. The hammers strike the rotating barrel with tremendous force, bending the steel to contact the mandrel inside.
If the offending machine work bothers you a bunch then you could always lap your barrel.
We shoot minute of plate, not minute of angle in CAS. Most of us accept that fact.