in the init line of the trigger add
civ3 addweapon "Weapon name"; civ3 addmagazine ["Mag name",1]
dont forget the ""
civ3 is the name of the civ who will be drawing the weapon
so change weapon name to what ever weapon class name u want, same with mag name but ofcoarse you add the magazine class name and 1 is how many magazines he will have, it cant be over 8 for pistols and 12 for primary weapons or it might mess up
heres the class names for all the weapons in arma2 http://community.bistudio.com/wiki/ArmA_2:_Weapons