For yourself and /u/Chip49, I'd refer you to this 2005 article in "American Rifleman" that actually has a picture of York in his later years with his percussion long rifle. In eastern Tennessee and Appalachia in general, the long rifle was still in isolated use in the 1910s because of its affordability. The ability to cast lead shot and use black powder instead of metallic or paper cartridges (combined with the widespread availability of black-powder weapons) meant it was the most affordable firearm available.

It was, of course, incredibly obsolete, and most hunters used other weapons, such as the lever-action or trapdoor guns that Chip mentions, and York was one of them. While he may have used a long rifle on occasion, his family's history shows that it owned many firearms, including more modern rifles and shotguns. These would have been the preferred weapons in most cases.

Some oral histories describe loose-powder weapons as hand-me-downs given to kids first. There are accounts of un-charged black powder weapons (no powder or shot, just the percussion cap) serving as toys or training tools for teens and pre-teens.