During the trek of Lewis and Clark there were of course no Hawken rifles as thiere expedition predated the American mountain man era In some areas there had previously been Voyageres. Lewis and Clark rifles by thiere own account were dissapointing due to the small calibers,and not adequate when used on the western bears. one of the best rifles they had was an air rifle thatwas very respected and admired by the Indians. It is now in the NRA collection courtesy of Mr. Beeman of Beeman air rifle fame . There is a very interesting story of how he found and researched this rifle an proved it was used by the Lewis and Clark expidition.I believe in Osborne Russel's book, he relates having a 30 something caliber rifle when he went west. Also the Lewis and Clark expedition had a small (.36?) that was one of the Captain's personal rifle. Neither of these were Hawken style rifles for sure, but at least give credibility to small bore rifles in the early fur trade, even if only 2 examples.
I'm sure , as mentioned, the movie industry in the 70's was not so interested in historical accuracy.
One scene shows the adopted boy randomly dumping beaver castor near a trap-a modern #4 Victor longspring. He is holding his nose. As a trapper myself, I find beaver castor to be a very pleasant scent. It is used in the perfume industry even today.
Respctfully B. Vanderhoof