Laz... a lieberal? That's funny! 
Hey Laz... thanks for the levity and the suggestions about the impact wrench/screwdriver. I have recently been successful at removing 2 (yeah, two of them) &%#@%&(*) set screws from a Poly and a Norc M14. Life is good.
I applied the techniques shown to me by some master craftsmen at a secret armory. I first selected the correct screwdriver (Chapman set or Wheeler set will do) bit. I was advised to select the bit on it's ability to fit the width of the slot and also be able to 'stand' up unsupported in that slot (almost a snug, wedge like fit). Then I was told to tighten and loosen that &^%$@ set screw along with some Kano Kroil penetrating oil (WD40 works also). Then after wiggling progressively back and forward, increase the distance (that's a linear measurement isn't it?) or tangential rotation as the screw loosens up. This technique worked for all of them and my M14's.
Life is good.
Hope it works for you!
We luv ya , Lazarus2009 !

Barney
Hey Laz... thanks for the levity and the suggestions about the impact wrench/screwdriver. I have recently been successful at removing 2 (yeah, two of them) &%#@%&(*) set screws from a Poly and a Norc M14. Life is good.
I applied the techniques shown to me by some master craftsmen at a secret armory. I first selected the correct screwdriver (Chapman set or Wheeler set will do) bit. I was advised to select the bit on it's ability to fit the width of the slot and also be able to 'stand' up unsupported in that slot (almost a snug, wedge like fit). Then I was told to tighten and loosen that &^%$@ set screw along with some Kano Kroil penetrating oil (WD40 works also). Then after wiggling progressively back and forward, increase the distance (that's a linear measurement isn't it?) or tangential rotation as the screw loosens up. This technique worked for all of them and my M14's.
Hope it works for you!
We luv ya , Lazarus2009 !

Barney