You may want to look at the specification on the calibers, +/-.001 is .002" tolerance. I agree you don't need any closer tolerance to reload, just like you don't need sub MOA accuracy, but it's nice.
Hey guy, you're the one that brought up "need" not I. My calibers measure to the .001, not a +/- .001, and as I stated anything smaller than that my mic's can more than cover it.
As far as sub MOA, a group at .317 Over all at 100 yds in .22 center fire comes out to .093 center to center group size. I believe that covers sub MOA.
Like I said, we're not building the next NASA space craft.