looking for some basic info on a possible set up i want to run with . any info would be greatly appreciated . i own a colt le6920 that comes with a 16 in. barrell. i am looking at the acog ta31roc for a scope . my research shows that they make the acog ta31 for a 14.5 or 20 in. barrell . in order to be able to use the sight marks on the rectical as desighned will eather one of these options work . this scope is set up for a possible 800 meter shot . but my guess is that my barrell length will play a big problem on longer range shots . i dont realy want to spend that kind of money and find out i need to change out a barrell to dial in my scope properly for full shot range spectrum . i have taken a look at the eotech as well and think the acog offers me more of what i want . what do you guys think????