Case weight can be misleading, what you need to be concerned with is case capacity. There is an article on 6mm Br..com about 243 cases and even though the weights varied significantly the case capacity did not. Sorry couldn't find the article again maybe you can.
The alloy and geometry can affect the weight without affecting the volume much. More than a grain difference in capacity and I will load them separately, usually with charges adjusted accordingly. Use MD's 1/4 rule to figure out what the adjustment should be.
