Any ar gurus here? I got a TA01 at a great price..problem is i like those hornady superperformance 75 grain HP's. They are pretty fast for 75grain (2910 fps) but the optic bdc is caliberated for the 55 grain ammo in a 20" barrel. Im putting it on a 16" 1:7 twist. How far off do you think the bdc will be?