Also confirmed, has happened to me couple of times with M4 and shotgun. I seldom end up shooting from prone position, so I've usually forgot this bug the next time I'm supposed to shoot.
Please fix the position of bullets leaving the barrel.
Also, the further improve the aiming system, I would suggest using the "dynamic crosshair"-thingie from Arma 3, so that if you aim at a target/wall/whatever right in front of you, the crosshair acts accordingly showing where the bullet will hit like in http://www.youtube.com/watch?v=LrydvG8DQIE .