I highly doubt any of them zeroed their rifles for 400. I'd almost bet a dollar, they zeroed at 100 and moved their turrets to the 400 yard dope, checked to make sure it was good, if they even did that. I'd guess they shot their guns enough to know they were good before they ever deployed. Having your turrets dialed to the ranges where most of the engagements take place sounds like smart thinking and since a fella or target torso has alot of height you stand a solid chance of being within killing center mass at 200 or even 500 when shooting gets fast with such a zero, holding a shade high or a shade lower.
Sorry, very bad writing on my part. Yes, they had normal zeroes (we got beat on if we didn't return turrets and parallax to 100 every time we reset or moved) and sometimes used an intermediate elevation setting. Othertimes they dialed for known distance, othertimes they dialed for known distance plus 6" (or whatever) so they could PID a target, othertimes they just used the reticle. But as you say they knew their gear frontways and back and used it in ways that civilians probably would not have thought of.
