True the Emil has mg ammo like water in an ocean(something like 50 secs of continous fire?!), but if you use it like that it'll eventually run out.
I did notice that it does almost nothing to a P.11 from dead six. My longest burst was when approaching one from behind, opening fire at 200 meters and firing until forced to break off(about 4 secs of continous fire). Pieces were flying like crazy but he just kept going and chasing the 109 ahead. That's pretty well considering the plane has no armor whatsoever.