My M48 build is giving me more trouble than it is worth. Now the rear action screw is stuck I can rotate it about a half turn but than it binds up. I have already shattered three tool steel bits trying to get it out. Any ideas? I have spared it with Kroil and PB blaster and it is still stuck solid. I am guessing some metal flakes/shavings are in the groves causing the screw to bind.