I was hit today in a game by an m4 with silencer, no acog, no red dot, and no grenade launcher but instead of bullets it shot out grenades as if it had a grenade launcher attached. I watched every kill cam after every hit where I was killed and this guy was going nuts. The only thing I could do in defense was grenade his whole team and we stole his victory in the end. I don't care if you believe me or not at some point you may meet him in game too.
P.S. When your game lags... grenades, clay more, and rocket launchers still seem to kill instantly. So use them when your guns don't work. Also since the last patch the hand guns are less effective so stay away from them completely. The MP5 seems toned down too so just switch stopping power or double tap for extra health if you still want major kills with the MP5 like the old days. The P90 is still usable after they retarded it (toned it down) too, just use stopping power, deep impact, and acog, then go run and gun.