I took a MP5 off a dead body. It was pristine and had a 15rnd clip in it (also pristine). I got into an engagement and tried to fire, yet it "clicked" as if there was no ammo in it. I removed the clip from the gun, put it back in, still cant shoot. Dropped it on the ground and gave it to a friend and they couldn't shoot it. They also saw a clip in the weapon. I'm not sure if this bug is only for MP5 or other guns as well.