Many gun owners do not own the special "Gunsmithing" Screwdrivers, also known as "Hollow Ground" screwdrivers.
Hollow ground screwdrivers have the working surfaces parallel rather than tapered. Tapered screwdrivers are a "one size fits all" solution, where as hollow ground have specific sizes.
See the graphic below:
This particular gun came to me in need of a reblue. One of the previous owners had used the wrong screwdriver on the grip screws and buggered them up good.
Fortunately the fix is relatively easy. The first step is to find a piece of scrap steel about 1/4" thick. Drill a hole slightly larger than the threads.
Next wrap the threads with masking tape to protect them and insert the screw into the hole.
You will need a brand new ball peen hammer (or one with a freshly ground face (imperfections on the hammer face can mess up your results).
Next gently tap the head of the screw, working in a circular motion, don't stay in one place.
Once you have the metal pushed back down, file the slot with a skinny needle file (to make the edges parallel).
I forgot to take a picture of that part of the process.
Next, remove the screw from the piece of metal and chuck it into a drill (make sure the masking tape is still intact, protecting the threads).
Get your self a piece of soft wood (like pine) and some sand paper or emery cloth (400 grit works best). Some oil like WD-40 or Kroil.
oil the sand paper and push the screw into the paper while turning it with the drill. You can push hard, the soft wood will yield to the pressure and create a divot for the screw head. The sand paper will get tore up, just move to a new section and keep going
Once the screw head looks good, you can step up to a higher grit for more shine or leave as is for bluing.
This is what they looked like when I finished. I should have filed one of the screws a bit more, but they look much better than when I started.
Here they are back on the gun after cold bluing them. I don't normally hot blue screws as they are too small for my parts basket.
I will try to flame (heat) blue some screws soon, I'll post some pics of that process.