We used PEQ15's mounted at 3 o'clock on the forward rail of our M4/16's They have both red and IR lasers that zero in conjunction.
The way we zeroed them was by using both a bore sight and the visible laser at the same time, out to 30m (I think, it's been a little over a year) with a buddy standing over the target and verbally guiding your adjustment of the lasers until they sit at the same elevation with a space of about two inches between each dot (bore sight left, PEQ on the right.)
Then once night fell, we'd night shoot using the IR laser and our PVS14D's on a helmet mount essentially shooting from the hip, or at least over your optics. It was just point and shoot.
I was impressed by the "accuracy" achieved with this method. Minute of man as long as you can see your laser.
Good luck!