Get Hawke Chairgun Pro and put your pellet in it with velocity if you can.Maximum zero range should generally be where you can get sub 1 inch groups or for an airgun where your bullet trajectory gives the maximum pbr, which ever is lower and normally rounded down to the nearest 5 yards.JSB Exacts (15.9gr) will give a pbr of 41 yards with a 35 yard zero if you can hold the groups.