I recently purchased a used equinox. I shot it several time before buying it, all good. Brought it home, waxed the string and shot it using the same bolts that came with it. The bolts are excalibur firebolts. The second shot it sounded like it dry fired, the bolt went about 10 yards, the target was 20 yards, and slid under the grass. Luckily I was able to find the bolt. Inspected the the blot and entire bow all looked good, extra emphasis on the limbs. Regrouped and shot again, first shot fine, second shot same thing, only this time could not find the bolt. Inspected the bow again all looks good. I was only using 2 bolts. I do not know if the same bolt did it both times. I weight the remaining bolt with the field tip it weighted 398.8gr well beyond the minimum 350gr. The only difference in the shots before I bought it and at home was:
1--The bolts had broadheads on them, I remove them and put field tips of equal weight.
2--waxed the string
Any ideas,as to what could be causing this, I am worried about blowing up the bow.
Make them fly straight, airplanes and arrows.