I don't think there's any "skidding." Every fired bullet I've ever seen has had very well defined rifling marks. If there was any skidding at all, the rifling marks would be indistinct or missing.just a thought for those better educated in these matters:
How much does the bullet 'skid' on the rifling? If you've got a 1:12 twist on a 3" barrel, does the bullet come out spinning at one revolution per foot? Theoretically - maybe, but actually? Or does the bullet not absolutely spin with the rifling and just get going at 'somewhat' of a twist.