Best app I have seen and used is iSnipe, only available for iOS on apple products. I wish they also sold it for Android.
The app data base of bullets is very rich, great flexibility for MOA, clicks or Mildot adjustments.
Got me to 600 yard target (55 gal drum) in 2 shots, prior to that, never shot beyond 100 yards. Helps if you know the velocity of the loads out of your gun, using a chrono.