I used a Redding BR-30 for .223 when I shot competition. I measured hundreds of throws with N-140, using a Redding scale, with and overall average of +.277 grains. Of all the measured throws there were some .00 - .05 but none ever went under the 24 grain target which "I" considered a real positive and to the plus side with a high of .53 of maybe 1 out of 75 throws. The bulk of the throws, 8-10 of 25, would weigh +.19 - .23.

This load was better than I was at 200-300 yards and would shoot cleans. I scale weighed all my 600 and beyond loads.
I bought a new Neil Jones measure some years back now but it has never been on the bench. "Popular" wisdom at the time was the Jones was a touch better than the Harrell's.
All said and done I guess I would put my BR-30 up against any scale system within reasonable price. The Prometheus, form what little I know of it, is another game and costed accordingly.