Time On Target, after doing some research on another well known site, there is well written opinions on that site from guys who routinely shoot to a mile or more. The general consensus of those shooters is that make sure to dead on zero at 100 yards, input correct environmental data, input accurate MV which you have and did. Test your drop data at 500 yards, which you said is spot on. The MV is the biggest concern out to 500 Yards, you can verify this by playing with your apps. BC doesn't really come into play until out past 500 yards, but since your MV is known to be accurate from your testing out to 500 Yards, they suggest it is a BC issue. You stated you can shoot to 700 Yards, if you can shoot further, the better, say 800 yards, then do a BC correction on your app until it matches what your bullet is actually doing. Your BC changes with bullet velocity. Hornady has data on the ELD bullets for three different BC's, depending on the bullet speed. Sierra does as well. I recently bought the Strelok Pro for $ 11.99 and it is well worth the money. Has the ability to set up to five different bullet BC adjustments along the bullet trajectory. It also allows for scope truing also. Once you adjust your BC to correspond with actual drop, move out to say 1200 yards and do the same thing for the BC at that range also, if you can shoot that distance where you are at. BTW, use the MV from your testing because you know it to be very close, if it aint broke, don't fix it, is the old saying. Try this on your ballistic app. You should be able to fix your problem on the app and then verify in actual shooting situations. IMO, this may help your situation. Don't over think it. If you start changing everything that you think of, you will just be chasing your tail. Good luck.