Using a crossbow for the first time this year. Bought a less expensive one to start with. Due to shoulder injuries can't draw a compound. Field points are hitting within an 8" bull at 30 yds. Have shot twice at a deer and both shots went low but heard one hit something in flight. Using 100 gr. 4 blade broad heads on same bolts as used for sighting in. What is the best way to weigh the different points? Will a powder scale work or is there something better? Have done no "fine tuning" as I would not know where to start. Haven't hunted with a bow for 50 years and that was with a re-curve and cedar arrows from Herters.