Weight is not a true indicator of volume, especially when comparing brass from different manufacturers. There can be significant differences in weight due to different alloys used that do not necessarily coincide with volume. Also when comparing military brass vs commercial brass, some commercial will weigh more than military for the same reason, different alloy. In fact that can be true even between different lots of the same head stamp. Assumptions can be dangerous. However weight probably will help consistency when the brass is same head stamp, same lot, fired and trimmed the same number of times.
