I did my Army service as service crew on the Hkp9 back in the 90 s ....... Not sure that the sight acually had a rangefinder.......... The whole system was built around using the helicopter from alreadyy preplanned firing positions mapped out around the battlefield they operated in. 1 company in a potential area for invasion by sea south of Stockholm , and 1 company in the area around certain rivercrossings by the finnish border....
there were never any "tankhunting"missions per se.....(Not the years i were around anyway)But i could be wrong , we did not tinker around much with the sight system.