I shoot F-class and 2K comps, and I haven't weighed a single piece of brass in a very long time…
Brass weight, compared in grains of water, means very little, sure, it tells you how much the water weighs, but it doesn't tell you the whole story if you take that number from a random piece and then extrapolate that number to every other piece. As
@Mikecr alluded to, it doesn't tell you WHERE differences may lie…
Not all forming/drawing is identical, the slug/cup the brass is formed from may all weigh the same, but if the draw causes thickness variation ANYWHERE in that case, volume is changed.
I measure volume in CC's, weight to me means nothing, of 20 random cases in a 100 lot batch, but I generally buy bulk lots of brass. 500-1000 depending on what's on offer at the time. I bought 5000 222Rem cases at one time, haven't even used 10% of them yet.
This measurement after ALL prep, neck turning, neck sizing to MY parameters, trimming and flash hole demurring tells me what is consistent and what isn't.
Never assume weight similarity means volume is the same.
I have Remington and Winchester brass from 20 years ago that weigh very similar, discovered when I weighed brass, and the volume is very different, sectioning a piece of each showed Remington internal structure very different to Winchester. Winchester has a thick web of .045", walls are tapered from a thick section near the web to thinner going up the case, Remington has a .030" thick web, heavy walls going straight up from the web and staying thicker for about 70% of the body. The Remington case has less volume, which is why loads from the Winchester cases are over pressure in the Remington brass…
Cheers.