First of all the percentages you cite are not all that bad. 100% is always a nice goal but reality is that if both lugs bear at least 25% of their surface at the same time, the action is probably OK. If you marked the lugs and then cycled the action though you may well have skewed the results. To properly check one needs to press the bolt against a solid stop then close the action. Pushing forward on the bolt then closing can tilt the bolt in the receiver and cause uneven lug contact. Closing the bolt against a solid stop helps prevent that. It's best done with the barrel removed, although is can be accomplished without. Lapping is best done with the barrel off the action. A bushing is screwed into the receiver and thru this bushing protrudes an adjustable lug which is polished and lubed. It bears against the bolt face and is the stop used when lapping the lugs. Usually the action is straightened before this is done. The front receiver ring is faced off with the action in a jig centered in the receiver. The lugs are lapped(they mau also be squared to the receiver ring face). The last task is to cut the bolt face square to the newly squared up action. This usually guarantees the barrel will need be set bad and the headspace adjusted. If you lap the lugs and the bolt face is not square to the action, there will still be a problem. A fired round can be checked for case head runout. This will indicate the squareness of the bolt face to the lugs with the lugs under a normal working load.... By squaring the lug abutments to the receiver ring first then HARD LAPPING the bolt lugs we eliminate this problem entirely.. In any case be certain to check the headspace after a lapping operation as it may change. A large enough change can make for a dangerous situation...
