Could anyone give me insight as to the purpose of the raised rib on some benelli shotguns? I have a nova and I shoot it very well on still targets (turkey heads), but can not seem to wing shoot with it very well. When I tried my buddies 11-87 with a flat rib I seemed to do better, but , I DON"T WANT AN 11-87. They felt cheap. I'm interested in trading on an M2, but it also has a raised or ramped vent rib. Can anyone help me to understand what the purpose of this rib is , or maybe tip me off to some sighting errors I might be making?