I'm looking for a sniper scope for my Ar15 that will be shooting .223 rounds. I'm wanting this to shoot out as far as possible with a 20 inch heavy barrel. I have two uppers, 1 in 7 twist and 1 in 9 twist. I'm wanting a dedicated scope built for the .223/5.56 rounds. I have heard there is one built strictly for the Ar15 platform and comes with a program for your computer that gives you estimates on your reloads and factory ammo. Anyone heard of such an animal?