My digital scale reads in .1 grain same as my mechanical scale ...
I gotcha. I think I wrongly assumed that they added a 4th digit (never had hands on digi scale) because I got a chance to borrow a friends digital caliper that had an extra digit and it proved to be a pc of junk.
My 550B powder measure is real accurate with ball or small flake like you say, dead nuts repeatable with BLC-2 (as long as the case slips smoothly onto the powder funnel. When I slightly miss the alignment and get the ker-chunk, then it's .5 heavy, always.)
I sorted a couple hundred 7.62 cases on the scale. I don't think I'll pursue that too much more!