Just to review, we are discussing emigrants from Britain, who came up the Mississippi from Louisiana to Illinois in the 1830's.
I hope some of our forum members from Britain will offer some comments, but until they do, I would suggest a couple of ideas. Happy, contented people tend to not leave their homes, unless they can afford to travel for recreation. This suggests to me that the British immigrants in question left because they were hoping to find something better. I don't think ordinary people in England had many guns, so I doubt they brought arms with them. I'm going on the assumption that these were people of limited means, and if they had guns, they probably obtained plain, functional arms after they got here.
Illinois went through a sort of population boom in the 1830's and 1840's. Leaders in the territory were hoping to achieve statehood, and they were recruiting settlers because the Northwest Ordinance required a population of 60,000 for a territory to become a state, and Illinois didn't have that many people. Land was cheap, which would have attracted would-be farmers who wanted a fresh start.
A lot of members on this forum believe smoothbores are more versatile than rifles, and were therefore popular on the frontier. It's hard to argue with that, but is there documentation? Washington Irving documented the American preference for the rifle in
A Tour On the Prairies, and W.N. Blane, who traveled the American frontier in 1822 and 1823, had this to say:
Twenty-odd years later, Granville Stuart suggested similar rifles were still in use on the Illinois and Iowa frontiers:
Stuart was familiar with percussion rifles, and one of his father's two rifles was percussion.
Regarding caliber, or bore size, this was typically expressed, as above, in balls or bullets to the pound of lead. Stuart mentioned a neighbor who had a rifle "...of large caliber for those days, using forty round balls to the pound of lead" (
Forty Years on the Frontier, p. 33). A round ball of forty to the pound would measure .488", so this would be roughly a .50 caliber rifle. Blane indicated that rifles of fifty or sixty round balls to the pound (.453" and .427", respectively) were considered adequate for buffalo and elk. He said that for general use, the favorite size was 60 (.427") to 80 (.388").
Stuart reported that the "rifle of large caliber" mentioned above was half-stocked, but he added that this was the first half-stocked rifle he had ever seen. So, half-stocks existed on the frontier in the 1830's and 1840's, but they would not have been common.
Many things are possible. There was a lot of colonial French influence in Illinois, so the subjects of this thread may have gotten their hands on an old trade
fusil. Rifles were carried and traded, and I suppose one of the British immigrants
might have spent six or eight months worth of his earnings for a silver-mounted rifle from Carolina. Stuart reported the presence of a half-stocked rifle, and there is the famous 1834 George Catlin portrait of Henry Dodge, in Kansas, holding a half-stocked rifle. However, it may be more productive to focus on what would have been
likely, rather than what would have been
possible. We are all entitled to an opinion, but based on the information the OP has provided, and a review of some of the literature, I think a fairly plain, full-stocked longrifle of .40 to .45 caliber, or possibly up to .50, flintlock or percussion, either brought in from one of the southern states or made locally in Illinois or Missouri, might be a likely choice.
Best regards,
Notchy Bob