To those who say you can't weigh the finished rounds to determine a double charge... You're wrong.
Separate the suspect batch by headstamp. If you have an "old" federal case with a slightly different headstamp, separate it from the others.
I have never had a bullet weigh more than 3-4 tenths of a grain off of what it should be, at maximum. I have used X-Treme plated and Montana Gold.
When separated by headstamp and weighed one by one, within the headstamps, the weights aren't more different than maybe 1 grain. I would certainly find an extra 5-6 grains if it were hiding in the case. This method accounts for the weight variances in brass across different headstamps. Try it sometime, you might be surprised how consistent the weights of loaded rounds actually are when separated by headstamp.
It will not work to discover overcharges, but it will work to find doubles or no-charges. Anything that is significantly over or under weight (off of the "expected" weight by 4-5 grains for instance) should be pulled down to check.
An additional QC step everyone should be using is your eyeballs. For loading pistol, you can visually look into the case and see the powder. If you know how it should look when appropriately charged, you won't have doubles sneaking by, even if they don't overflow the case. Always look into the case before/while seating a bullet, and don't put a bullet on top of anything that doesn't look right.
