"the shizz" is that start of where one would begin to wonder if it was serious, and the SHTF and post apocalyptic nonsense.
And the mention of using an ACOG on a 338 Lapua for 1000yards is another.
At first thought it would assume you were BSing or very new too shooting.
Did you do any distance shooting with your ARs? As in 300, 400, 500 yards?
If not, I would recommend something that is not going to punish your shoulder or your bank account whilst you learn't to shoot at those kind or ranges, before you look into something like a 338Lapua, or even a 7mm Rem Mag.