I have an AR with a XPS 2 on top rail and laser on side rail. The laser drifts off of alignment in relation to the HWS image based on distance to target. What would cause this? Cheap laser???
Each accessory is "zero'd" at a particular distance, and each accessory is mounted at a different distance from the bore (aka mechanical off-set). The two will very rarely coincide with one another.
Measure the distance from the laser to the bore. Adjust it so that it is that same distance to the side of POI at your target. If it is parallel to the bore (looking vertically) you won't have the left-right drift as distance changes.