Apparently the authors did not do enough research about how the firearms really work. Were you ever at a real shooting range? Were you even wielding a real gun in your life? Who told you that bullets fall that much at such a short distance? No weapon factory would be allowed to produce such a crap! And I agree with @blyndid about the ridiculousness of the mouse clicking sensitivity (smgs especially) and remind the authors that real weapons got different modes: for example a real MP5 can fire bursts, three bullets at the time and even a single shot.