I kind of find myself debating which bomber can carry the heaviest load, the early B-386 Mammoth or it's successor, the B-948 Collosus, so that led me to do some testing. I already knew that the Mammoth had issues starting at 15,000lbs, due to the fact that it had to carry twice the weight of the bomb (counter-weight on other wing). This made me decide to stress-test the Collosus. So I built a 25 ton bomb. 50,000 pounds

Empty weight of the bomber, with fuel only

Proof of the bomb's weight

And here is the video showing off the test. I think we have ourselves a winner.