The best trick I have learned about not buggering up a screw is to never try to turn it. Hard to not do sometimes I know but I have stopped taking things apart at last. Just wish more than a few gunsmiths would do the same. I've had more than one gun returned with a screw that suffered from a trip to the gunsmith.
There is always the potential to mar or bugger a screw when tightening or removing, especially on old vintage guns where they may be a bit stuck after not being turned for 100 or more years. The temptation to be impatient instead of giving penetrating oil time to soak in may result in a bit slipping or even breaking.
I have a D.M Lefever crossbolt that has perfect screw slots. I would have bet they were never turned. Then I was reading an article in Double Gun Journal on the D.M. Lefever crossbolt guns by retired Oregon gunsmith Keith Kearcher. He had photos of one of these guns in a very disassembled state to show the internal mechanism. I thought the four digit serial number seemed very familiar. I looked at my gun, and was surprised to see that it was mine that was the disassembled gun in the photos. Kearcher hadn't left a mark on any of the screws... as it should be. There is a difference between a gunsmith and a mechanic.
