Originally Posted by
SLG
I don't know.
I have swapped guns with many of my teammates over the years and found that we had the same zero. It's easy ot figure that part out. As for "what a zero really is", I don't know, and I don't know that it matters. Whether mechanical or as a compensation for some physical "limitation" (for lack of a better word), it doesn't really matter. All that matters is that it hits where you want it to hit.
Given 2 or 100 shooters, in the prime of their life, with excellent fundamentals, and high quality equipment, I have found that a "zero" is a zero, regardless of the individual.
That can and will change from group to group.
Anecdote that I don't know as much about as I would like: During Vietnam, snipers and spotters would share one sniper rifle, in order to give the sniper a rest from looking though the scope. Whether it was ever a problem or not, IDK. Guns were also less precise then, so again, IDK.