You do not know the velocity and your making hits on targets at 1300? What did you do just make your own drop chart from actual drops?
EddyBo
After establishing a foundation zero from 200 yards I walked it right on back to 1300 using experience based on 60 years of shooting long range!
Pretty simple really!
Gotcha you walked it in, I have had to do the same with subsonic rounds. I cannot make a balistic program work with subs worth a darn. I am more into making first round hits at unknoown distances using a LRF and a ballistic program. To do it my way knowing your velocity is very important.