I'm trying to remove the stock front sight on my Ruger Mark III so I can replace it with a Hi Viz fiber optic sight. My problem is that the front sight screw won't budge. I've managed to get a screwdriver that's just the right size, not too big, not too small. But no matter what I do, I end up coming out of the slot and I'm starting to mark up the screw head. I've stopped trying so I don't do any further damage. I've searched Google as well as the forum and still haven't been able to find a good answer. I did find one suggestion to use heat to try and loosen it. But no other real good suggestions. I'm surprised I'm not finding an answer in my searches, so I'm going to throw the question out to you folks. Any ideas on how I can get this screw loose without marring the screw head or front sight in the process?