Download from here : http://savefilefree.com/Orella90612/BlackOps
Basically, use the variable scope, and zoom in with it atleast to the second zoom, or third. And by doing that u don't have the stupid 2 second delay of ur bullet not going straight. Drag scoping is basically what it is, were just kinda eliminating the bullet flying randomly. Practice it. In this video I was just figuring it out pretty much. So I haven't practiced it that much but it clearly works.