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[red_star_republic]

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[EvolutionGSR]

If you want to get closer trajectories why not go with the A4 model for the 20" barrel?

[SuperSet]

Depends. Youre going to need to do some homework to see if the subtensions match:

http://www.calguns.net/calgunforum/showthread.php?t=452594

[WDE91]

18" barrel screams for a 1-4,1-6 or 1-8

[pyro3k2]

I am running an Acog adjusted for a 20 inch barrel on my 16 inch and only notice the BDC being off past 300 yards. inside that range it's spot on. with an 18 inch barrel I would just get the model for the A2 style and not worry.

[tenpercentfirearms]

That ACOG will work with any rifle. Will the BDC be on? You never know with any scope until you try it. Different loads behave differently, so it is always kind of ball park. Just learn how to shoot that optic with that rifle and practice.