This happened to me the other day. I was playing on Depot and as I rounded a corner in the tunnels, an Axis guy tossed a grenade directly in my face from a distance of about 10 feet. I was naturally shooting at him with my mg but the interesting thing was that as the grenade neared the end of my gun it was deflected from its trajectory and I watched in disbelief as it flew backwards (that’s right, BACKWARDS) toward the Axis guy who threw it, giving me just enough time to duck back around the corner before he was blown to bits. I have tried to recreate the situation without success. It would appear to have been just dumb luck because I certainly was not shooting at the grenade.
Has anyone else experienced this? I realize that the chances of such a thing happening are extremely low but it’s pretty cool that the game physics allow it.
Now if I could only learn to shoot a PF round back at the &$#er who fired it! 
