On an ar 10 i would go 2-12x42. The 6 times zoom gives you 12 power with a very wide field of view. Also a red dot is available and a must on that gun. On my .22-250 i have shot out to 800 plus with my 2-12x42 vx-6. At 500 yards 12 power is more than plenty of power. IMO higher power scopes...