Goofs

Uranium was not known to be dangerous until well after the end of the nineteenth century. There would have been no reason for Jules to connect health problems with the pitchblende which was being mined.

Uranium is a heavy element and supposedly is in lead lined boxes. The empty lead boxes containing uranium would have been difficult for two men to load into a wagon. Even partly filled with uranium the boxes would have weighed more than the entire group of people could have lifted.

Contrary to the statement made by Sam, the army used hydrogen balloons in the Civil War, not hot air balloons.

The revolver chambers are visibly not loaded.

Rose Hilridge (the bounty hunter)'s gun is a Smith & Wesson Military & Police Model (.38 special) double action revolver. The M&P wasn't initially developed until 1899 and her model is an early 20th century variant. In fact most of the handguns are too modern for the time period. Only some Colt 1873 Single Action Army revolvers seen in the background (that are never fired) are not anachronistic to 1892.

Several of the revolvers used in the film are modern stainless steel guns with vent ribs on the barrels.

Uranium isn't explosive and can't be ignited by dynamite. Uranium-233 will "go supercritical" and result in a nuclear explosion if more than about 33 pounds are formed into a perfect sphere (more is needed if it is shaped differently. Other isotopes of Uranium have even larger critical masses. Since the Uranium in the boxes hadn't already exploded, they must not have contained the critical mass of uranium and blowing the boxes up with dynamite would only have scattered the uranium making it less likely to explode.