Both Uberti and Winchester chamber their model 73 in .44 Magnum. The modern 73's can handle factory .44 magnum pressures. This is a far cry from black powder .44 wcf pressures.
As for the 73 being a weak design, I think a lot of people just looked at it and thought that looks weak. Actual testing by Winchester on the '76 (same design) showed that they could not destroy a receiver with tremendous amounts of powder and several bullets in the bore. Eventuallu the barrel burst in front of the chamber. The receiver was unharmed, even the smaller pins etc. Testing on a '73 was done, to the point of removing a togg;e link and firin it, and the rifle handled it fine. Removing both toggle links resulted in the action partly opening on firing but no more.
The design itself is stronger than people think.
