So just out of interest I asked a lab friend of mine to measure the weight some of the BBs I have, all Vorsk ones.   Here's his summary.   Weight       .43g     .4g       .32g   Mean         0.424   0.404  0.324 SD              0.002   0.004  0.001 RSD            0.5%     0.9%    0.5% Median      0.424    0.403  0.324   The BBs were measured, 10 of each from a bottle,  to 4 decimal places.   Mean is the commonly called average, SD