The more square the round is hitting the object the better, the difference between a deep penetrating .50 cal vs. a grazing or ricochet. Difference between hitting a man square in his jaw, vs. glancing off his jaw bone.
Keep in mind that the .30/.50 cal MG projectiles behave very different than the projectiles of the 20mm, 30mm, and 37mm HE and it has very little to do with the "sahpe" of the projectile. I understand the thoughts on the "shape" or "ricochet", but it doesnt apply here as much as one might think.
