J
Jose
You must be an excellent shot to be able to do MOA at 600 with iron sights. I can barely see the target at 600, never mind get MOA grouping.
Remember what I said: with the right target.
The targets used in NRA Highpower Rifle and in CMP EIC matches are all designed to be seen by an unaided, healthy eye all the way to 1000 yards.
The black bullseye is always 6 MOA +\- regardless of the distance. That means the 600 yard NRA rife target has a 3 ft diameter aiming black.
As long as your distance vision is good (or corrected to be good) and you can focus on the front sight, NRA highpower is not a seeing game.