Since this is Benchrest.com. I assume we are talking about custom bullets, out of the same die, all made at the same time by an indivudule who knows what he is doing.
That does not include such "match" bullets as Hornady, Sierra, and other mass produced offerings.
While I have not done it lately, in the past, when I did take time to weigh true match bullets, they were within the tolerance of my scale.
I had the loan of a Juenke Machine a while back, and checked several brands of custom bullets. All showed about 3 to 4 "lines of deviation", (what ever those represent), except one particular bullet. That was the BIB. When placed on the machine, the needle would just kind of quiver. While this does not prove anything in particular, the fact that the BIB sort of sets the standard in 30 caliber bullets does.
As for using a dropped bullet. Come on, guys. We spend hours at the range, THOUSANDS of dollars on equipment, not to mention the ever increasing cost of getting to matches. Many of us go to matches with on intention. To Win.
I would no more shoot a dropped bullet on my record target than I would use a dropped case with a bent neck. I can use it to fireform, or to foul the barrel. But in this game, worrying about saving a 25 cent bullet just doesn't make much sence in the whole grand scheme of things.........jackie