I know for a fact that the yard I use here is right on, no bobbing around. Although a few around here that I have read about on here like to keep the scale inside, thus allowing them to say whatever they want. And I have weighed about 10 lbs of copper at home took it to one yard and they show it at 6.5, but that's a different story. Just goes to show that you need to be safe and have a good idea in small amounts before you take everything in.