As an aside, the guns are so weak that you really need ALL of them hitting the same spot or you'll never get kills. To that end, you also NEVER want to fire outside 200 yards (150 better) because these rounds lose almost all lethality outside that.
So, in the long run it doesn't matter because the guns should never have different convergences, and they should never be set out to maximum range.
Other than that, sorry for butting-in.