help with func_tank (mounted gun)

ok, so i am almost ready to make my first relsease of my map, but i am having problems with a func_tank (mounted gun) ok, so i got it to look where i want, but i cant get it to fire, when i press the fire key, nothing happens, if anyone can help (like specific settings, comon mistakes, whatnot) please.

Tutorial: Mounted Guns in Orangebox

i think there is a problem with func tanks in garrysmod, becuz i changed my func tank a bit, and it makes a firing sound, but it dosnt shoot bullets, believe that