Its hardcapped to 65m nomatter what. The reason why its possible to hit stuff on up to 67 (siegeweapons even further) are the hitboxes which are larger than the number on the crosshair shows.
You need 50m distance range bonus to archive that, since skills have a base of 15m. To reach the cap you need the archer perk (3×7m cap increase and a high tension bow+5m elken passive +distancecap) you will come close with a Legendary or even epic high tension even without an elken. With a legendary ht-bow you will miss 0.25m to the 50m cap, so elken is not necessary at that qualitylevel anymore.
To fill that 50m ranged bonus you need to roll a bit extra rangebonus on the bow and even it out with rings depending if you want to drink carrotjuice or milk and if you want to pick sharpshooter+arcane archer or only one of them. The math is on you at this point