A few of you have explained that you either weigh individual completed rounds or boxes of completed rounds to ensure you didn't short or over charge with powder. With the variances in bullet weight and case weight how can you tell especially in 9mm? I would imagine that there could be a big difference between individual completed rounds even if everything was done correctly.
I have weighed bullets and found some that were off by a couple grains, coupled with the fact that cases can be a couple grains different completely makes finding a over or under powder charge impossible in some instances.
I wouldn't depend on this as a fool proof method of checking cases. I ALWAYS visually inspect each and every case for a correct powder charge. I also measure each 10th charge on the scale. Call me paranoid but I would rather be safe than sorry.
Just my 2cts