Just bought a used rifle and wanted to switch out the scope and mounts but when I got the mounts off it was apparent they had been loc-tited on and now there is "residue" I'm having a hard time getting off the top of the receiver....My Question is "How Do You Get This Stuff Off Without Marring The Metal"?

Use heat. I'd use a propane torch set low and make a scraper out of a popsicle stick. You will have to get it a little hot but not hot enough to ruin anything.

Make a chisle out of soft brass and scrape it off, this works well, OR use a hand torch used in cooking to melt stuff like suger in spoons, it is propane and has a small flame, it will also clean up the holes but better to run a tap into he holes.