You ever weigh something and be surprised what it weighs? We have a lime/fertilizer spreader that pulls behing a tractor. I can get about 7.5 tons of potash in it without having to shovel it in the corners. I needed a little lime, so I went to the local elevator and told them to fill it up. Before it was even full, I noticed that the tires were really squatting so I had the loader stop and I weighed it, before checking the air pressure at their garage. It had over 11 tons on it and I think a little creative loader work could have got at least 2 more on there! The tires were not very low, but I pumped them to the max and took it very easy until i had some load off it.
7.5 tons of potash, supposedly 70#/cu ft fills it. A similar pile of lime would have been at least 13 tons and i think lime is supposed to be about 100#/cu ft. Hence I was surprised at the weight.
Another one that surprised me is the difference in weight of different corn silage varieties at the same moisture content. We bought some corn silage in the field a few years back and weighed the loads. The silage was about 35% dry matter, it was a grain type as opposed to a specialty silage type, and it weighed about 8 tons/load on 18 foot gehl chopper boxes. The last few years we switched to a small company that makes a silage corn geared for high digestability for most of our corn. We broke quite a few running gears the last few years since switching. Most of the time it is the centers breaking out of the rims, blown tires or front spindles breaking in two. One time we broke a frame runner! We emptyed two of the grounded wagons(also 18' gehl) with skid steers into our feed trucks, which have good scales. They averaged 11 tons per load of silage, also at 35% dm. You could probably add close to a half ton of spillage to that also as skidsteers are not the best way to unload a forage box, but your options are limited when the nose is down and a broken spindle is buried somewhere beneath the pavement. I thought it was significant that this silage corn is so dense, and also noticed that it settles less over time in storage. BTW, it is not bmr corn and we did combine some, but the combine does get a workout.