As long as I have been around gun's I have no idea what trigger stacking means's , anyone ?
im taking a shot in the dark with this guess,
but, maybe it means when you combine all the firing functions of the guns into one trigger instead of each gun haveing there own seperate trigger?
similer in our planes, how if you pull the trigger on the joystick, it fires all the guns in the plane(trigger stacking)
but if you push n(i think?) it only fires certain guns.
idk, that was just my guess.