Good question! I had wondered the same thing myself, but recently discovered that George Bent provided the answer (at least for the Cheyenne):
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This is a page from
The Life of George Bent, From His Letters, compiled by George Hyde and edited by Savoie Lottinville. This is the way I loaded when I tried wadding with bark: powder, wad of shredded bark, ball, wad of shredded bark. I did use undersized balls (28 gauge or 0.550", and 0.562") in my 24 gauge (0.579") trade gun, because the 28 gauge balls were generally carried by the western trading posts, and I wanted to see how this outfit would perform. I then tried the slightly larger 0.562" balls with the same loading sequence to see if they worked any better, and I could discern no salient difference. I found that this method was not particularly accurate and created a lot of fouling, which required frequent wiping, regardless of ball size. That may explain why this fellow, an Assiniboine hunter painted from life by Karl Bodmer, carries a separate wiping stick:
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Look closely at the stick he carries vertically in his left hand, and you'll see a wad of something (?) affixed to a worm on the end.
The next picture (if I remember correctly) is a Hollis trade musket either from the National Museum of Natural History or the National Museum of the American Indian. Coincidentally, it was collected from the Assiniboine people. Note the wiping stick, with a jag carved in one end and a wire coil "trade worm" on the other:
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Based on my own field tests, I don't recommend shooting a trade gun this way
for optimum performance. However, I do think I now have a better, first-hand understanding of how guns were shot back in the "Shining Times," and a solid basis for comparison.
Best regards,
Notchy Bob