Need advice on range and sighting in of 308 I built

I built a 308 using the CMMG lower for g3 mags, have a DPMS upper, 16 inch Criterion barrel by Krieger. It is my first 308. What should the max shooting distance I can accurately hit a target? What would be the best way to sight it in to be able to shoot from 0 to its max distance. Plan to use it for security at small airport my parents own. Using dot sight with flip up irons. I know with my AR-15 I sighted it in about 1.25 inches below bulleyes at 50 yards and can hit with in 1 inch of the target from any distance between 0 and 200 yards.

Hey, does anyone have some tips they can share

I bzo my FALs at 25 yds so it would be on at 200 yds as well with M80 or equiv. There was just topic on arfcom or the files about bzo for a 7.62 Ill see if I can find it.

ETA: I dont know if you can post links to other forums so Illl just link the pic here

As far as how far you can hit with it, with a red dot and optimal conditions (ie range, not a windswept tarmac) I would assume its capable of com hits at 500 if you do your part.

Thanks, I am a newbe and appreicate guidance