I've heard that 8 grains of brass has the same volume as 1 grain of smokeless. I usually weigh a sample of each headstamp. If weights are very close, it makes no matter. In HOT rifle loads, I use a particular headstamp for each load. It does two things; 1. It helps to ID each load, especially when carrying more than one type, and 2. the risk of an overload is minimized.
I sort my pistol brass the same way, but keep track of which headstamps weigh close to the same as other groups of headstamps, just because I have a neat AWS 100 that makes it dead easy. For loads, in pistol especialy, where max loads are not at issue, it makes no matter. ( For BP loads I have a couple of brands of brass cases I like to load, especially the ones selected for match use. For practise loads I will use up any nickel cases I have around, plus much of the near wore-out, & small lots of misc. cases.)
I have lots of time on my hands!