Just sharing something I do to check collimation:
Instead of shooting any rounds, I cowitness a vis laser with the day scope at whatever distance I'm checking out. On the same target, I'll place a thermal target (usually a small square of aluminum foil). Slap on my thermal clip on, with the gun on tripod, point the laser into the center of the foil (confirm this with a separate day optic), look thru in thermal view, and note the shift with the reticle.
This helps with being about to see small shifts (if you care). If you have .2 of shift in the same direction of spin drift, you could be doubling your spin drift effect at 1k, which might start mattering? mileage may vary.
LOVE that idea! I’ve struggled because as soon as you touch the gun and mount the thermal, no matter how tightly you’ve cinched it down, it move.
GREAT idea!!!