I switch between an ACOG-3x, 3x9 Mk4, and my stock, open sight handle on my Colt HBar. All have the same height from the bore, about 3.5". I left the stock mil spec front sight on with no distortion issues. Impact is within .75" at 100 yards with all three sights using a 40"/# of torque. This is with 55gr. factory Remington Accutips , and 62 gr. Green Tips 556 . It might be better, but this is the typical accuracy of this rifle.