Butch,
I know you're not a fan of lapping in bolt engagement on factory actions, and you've repeatedly stated what appears to be a logical reason why, primarily about the static mechanical conditions immediately prior to firing.
That said, there seems to be a body of empirical evidence, including some experience of my own, that lapping for at least some obvious contact on both bolt lugs does show an improvement under the dynamic conditions during the actual firing event. This IME is mostly evidenced by the rifle being less picky and grouping consistency for a given load when it's near top of the pressure range.
m
Mathman, glad you have all the scientific equip. to back your thoughts.
44hunter45, if you want true lug engagement you will have to bush the OD of your bolt to get rid of the slop. If you cock your bolt, the back of the bolt lifts a bunch in the rear of a Mauser especially. When that happens the upper lug is not engaged with the upper lug abutment. Bolt lapping is a futile exercise that makes a gunsmith extra money only.