This thread made me think of something else:

I see a lot of old guns with buggered screws, some of which can be hard to replace. I've not seen it discussed on any forums, but an old machinist showed me a trick which can work wonders. You have to choose your projects, of course. Some should be left alone, and some are too far gone, but there is a broad middle ground which will benifit from the work.

Grasp the screw in a vise, between blocks of wood. Get a small ball-peen hammer with a smooth face and start tapping at an angle on the screw head, bumping the metal back into place. You also need (to renew the slot, which will frequently close up from the tapping) needle files, a sharp fine hacksaw blade, and perhaps a Dremel. Polish with emery cloth before refinishing. No two cases are identical, and the fix may not be "perfect" but it can often produce a huge improvement, on a middle-grade gun.

Practice your technique on a few worthless screws before you tackle something important. The key is the tapping, to return the slot as close as possible to its' former shape - just polishing off the burrs (as is sometimes encountered) doesn't do the job.