Thanks for your reply Johnnyboy, picking up the tube and using the assigneditems command only returned items such as gps, NVGs, etc. As an experiment i also tried using additem when the player enters a trigger area, however this proved fruitless. perhaps mortar pieces are classed as a vehicle? in the editor the mortar pieces and other such weapons are classed as dismantled weapons, but ive no idea how to call such items
looking in the config viewer, the mortar pieces are in the vehiclecfg folder.
EDIT: Got it, its done with *variable* addbackpack "I_Mortar_01_weapon_F"