Well, grenade launchers should at least go in the general direction you fire them in! From what I have seen they sometimes tend to drop at your feet. A grenade launcher is designed to do what it says - launch a grenade further than a man can throw it, and a man can always throw it further than his own two feet :-). It should act like a Rocket Launcher, but with shorter range.
At the minute its implementation reminds me of that Taliban terrorist on YouTube who fired an RPG into the wall right next to him...