Hi,
Hopefully, you will look at some of the books about long rifles. Kindig's, Shumwya's, and Hansen's books will get you started about the decorative trends in American rifles. The topic of ornamentation could fill chapters. Despite the notion that the "average rifle" was plain, consider that almost all of the rifles in those books, decorated or not, show a great deal of wear from use. I understand that it is intuitive to think that the "average pioneer" in colonial times and in the early US could not afford a rifle with some decoration, but that is a notion not backed up by evidence. For example, consider Davy Crockett's first gun, a fine York county rifle with engraving and carving. Based on data evaluated by Bob Lienemann, who co-wrote a book on Moravian gunmaking, around the period of the American Revolution, a good rifle with some carving and a couple of inlays might cost about 7-9 dressed deer skins. Given a rifle would not be purchased every year, that cost was well within the means of a frontiersman. Also consider that the average long rifle was probably not purchased by a pioneer but by a farmer or local merchant, and very early on, Indians. During that era, farmers and merchants often were prosperous people and mostly not dirt poor hardscrabble farmers. I suspect, like automobiles today, people purchased as fine rifles as they could afford, particularly during the era when even the simplest objects usually had some sort of decoration if made by a professionally trained craftsman. With regard to trends in LR decoration, guns during the colonial period and "Golden Age" (17??-1820) often had carving and a small number of inlays. The earlier the period the better the carving and later it becomes more stylized and simplified. During the 19th century, carving began to disappear until after 1820 or so it was rare. Metal inlays, engraved or not, became more popular until they dominated after 1820 or so, often without much artistic merit. This was also the time of Leman, Dimmick, and Henry trade rifles that went west and were plain except for patch boxes, simple engraving, and sometimes checkering. So the issue of ornamentation is not simple and it is probably not correct to say the average long rifle was plain. I was at a re-enactment fixing muskets and rifles while a re-enactor friend was discussing Rev War rifles and rifleman to the crowd. I previously helped him find some documentation for his plain rifle with only a grease hole in the butt like many southern mountain rifles from the 19th century. After sorting through 50 or more examples of Rev War vintage rifles all of which had some decoration, I found one gun that was plain with a grease hole. It is at Valley Forge and it is very odd because the breech third of the barrel is square, not octagon. My friend was happy to find an example somewhat similar to his gun. As he was talking to the public he held up his rifle and claimed that it represented the plain rustic rifle that most rifleman carried in the Rev War. I could only wince.
dave