you don't. 27th shot. while in close range, count them and right click the target you want to OC just before the 27th shot just before, because if you do at the begining the com will just fire at the range of the normal gun so if the target is a mobile target it will probably move out of range of your dgun and it won't go off because your commander has no reason to move foward if his order is to shoot at unit and he's doing it at the range of his normal gun.
