What you're describing is a co-aligned zeroing method, and generally the easiest and simplest way to get a practical zero on a carbine with a sighted in day-optic and IR laser--aim the day optic at the furthest well defined aiming point you can find, lay the rifle steady on the target, then adjust the laser to coalign with your day sight's POA.

I would not worry about etching the reticle into the tube if you're only mounting it behind the optic for zeroing.

The problem occurs when the NVD is hard-mounted behind an illuminated optic without NV settings for a prolonged period of time--put in the simplest terms, this means that the exact same part of the image tube is being exposed to a "bright" light source, thus "burning" the image into the tube.

For hard-mounting and/or static observation, the rule of thumb is that if something is bright enough to be seen with the naked eye, you probably shouldn't leave an NVD trained on it for a prolonged period of time, as it could result in damage to the tube, however, if you're constantly moving and not staring directly at bright light sources, you can work in mixed light environments more or less indefinitely without issue.

Similarly, for a short duration, like setting a co-aligned zero should be, putting the NVD behind an ACOG should not be an issue. If you're doing it alone, hard-mounting the NVD might be an option, but with as short as the eye relief is on ACOGs, you may not have room to hard-mount the NVD behind a properly zeroed day optic.

The easiest way to do this is to just have someone helping you--pick a far away aiming point that is well defined (e.g., the corner of a building), typically at least 100m away (I prefer 200) depending on your likely engagement ranges, and look through the day sight with the NVD and have your partner either look through their own NVD, and adjust the laser to the same aiming point while you hold the weapon steady on, or if you only have one NVD, just give them directions for which way to adjust the laser on to your POA.

With the NVD mounted behind the day-optic the fact that the PVS-14 is not collimated will not be an issue, this is only an issue when placing optics in front of the day sight, because you are basically superimposing your day sight reticle "over" the NV image. Thus a non-collimated device will "shift" the image, meaning that the optic's reticle will not be in the same place relative to the background.

When mounting an NVD behind the day sight, you're viewing everything through the optic, so the laser, target, and reticle will all maintain the same position relative to one another within the NV image.

~Augee

DTs

~Augee