Many AH pilots don't realize this because they spray and hope for 1-shot kills, but on non-explosive rounds (i.e. "bullets") the closer you get the stronger they hit. They fade and weaken as they travel downrange. They lose their kinetic punch. Firing a 30cal at 800 yards may hit but do no damage at all. Firing a 30cal at 100 yards is lethal.
2x12.7mm are more than dangerous if you get CLOSE enough. If you're in a situation where you CAN get close enough, it means the other guy is slow, and now you are in a much more manuverable plane and can stick on him like glue, killing him.