Although I spot check batches, I pay close attention to the weight between each other relative to the mould suggested weight. Since I cast anywhere between .22 - .580, obviously there are looser tolerances on weight as you go up. .5 - 1.5 grains variance is what I remember, but I can't remember the caliber. Throwing back defects is a great way to make casting more consistent. If you can cast all of the same slugs in one run, that is even better. I will now document the variances in my worksheet on particular moulds. It is an important metric, as the name of the game is consistently.