Come off it, that time period has become such a niche part of the film industry if we want to see that type of thing you have to accept a little give. I'll take that over a generic action movie thanks.
Besides you've missed on far bigger issues either the film anyway, loading powder and then shot without wadding, not priming, closing the hammer on a clearly empty pan when shooting the bear all pale in comparison to the fact that the true story occurred on the plains not BC forests and in summer winter. The director did address this though and said he wanted the audience who wouldn't be familiar with the kinds of struggles these people faced to relate in ways that would still make sense today I.e. dank and freezing.