turrets help

[Q}Me]

hi
i tried to make one of those combine sentry turrets, but it just didnt work out. i tried prop_physics 1st, and then setting the .mdl file for it, but that didnt work. i tried tank_ as well, but i couldnt get that working either.
can anyone help pls?

 

[bliink]

hmm all i know is that its an npc called npc_turret_floor