Yeah, don’t buy stone or fines on a rainy dayI ran a rock crusher for a few years while I did maintenance on heavy equipment. I live in the PNW and all the yards push selling rock by the ton. The yard I worked for sold it by the ton. A reason was because we could scale trucks, versus measure volume.
On the other hand we always measured our volume to weight in the summer.

The loader they’re using puts 4 tons in my trailer without even emptying the bucket
