found a great rangefinder app for andriod, actually made for golfing, but very easy to use and very accurate, called simply GPS rangefinder, not sure if you can see the target, just left of the right electrial tower way up on the hill, the bare spot with no grass
so i made a target, about 2 feet wide and 4 feet tall and put it out at 600, staying level with elevation
when i finally figured out how to get sighted in, i was out of ammo and the wind was ferocious, but boy was i happy to see some punches on this target, you can see one on the paper, one above, 5 under it, one though the stick, a couple n the rocks and a few in the cardboard on the left and right side
now that i know where i am at, ill be able to refine my grouping next time
had ALOT of fun today, and next week you should see some impressive 600yard grouping from a sub 500$ ar with a sub 100$ scope(fingers crossed)