Well, CW and CCW are self-explanatory, but what isn't is which way you should be holding the gun while you make your CW or CCW turn, since one way is actually the reverse if you hold the gun the other way. Looking down the sights, turning the barrel left to right is clockwise, but looking down the opposite direction, that's counterclockwise. Does that make sense?
But you're right, perhaps more force is in order
RE Hex screw: yeah, that's the first thing I removed before trying anything.