Why do you question the ability of a 502 scale? All the RCBS/Ohaus range, 502, 505, 5-10, and 10/10 all use exactly the same floating agate bearing/knife edge system, the parts are interchangeable. The 10/10 is no more accurate than the 502. When carefully prepared they are sensitive, repeatable and reliable. As with all scales, use of a set of check weights is part of the routine.