There was comparison test done by LASC and both CH4D and Redding produced lowest average SD numbers - https://www.thehighroad.org/index.php?threads/c-h-502-micrometer-powder-measure.761239/CH4D vs Redding ... Does one pull better?
Depending on the powder used, SD number varied between the two.
SD - CH4D / Redding / Harrell / B&M / RCBS / Lee / Hornady / Lyman 55
AA #9 - 0.000 - 0.000 - 0.000 - 0.000 - 0.032 - 0.000 - 0.043 - 0.037
I 4227 - 0.025 - 0.032 - 0.038 - 0.102 - 0.000 - 0.051 - 0.031 - 0.061
Unique - 0.145 - 0.127 - 0.150 - 0.100 - 0.129 - 0.142 - 0.139 - 0.185
I 4198 - 0.138 - 0.177 - 0.103 - 0.125 - 0.169 - 0.141 - 0.170 - 0.114
SR4759 - 0.128 - 0.099 - 0.151 - 0.127 - 0.146 - 0.157 - 0.135 - 0.205
Average - 0.087 - 0.087 - 0.088 - 0.091 - 0.095 - 0.098 - 0.104 - 0.120