You are wrong on this. I have done a lot of research on late 18th Century arms in the new Republic and their were quite a few a rifles around at the time, but the vast majority of Americans at that time owned and used smooth bore guns, also known as "fowling pieces." One could fire it either with buckshot or round ball, just like todays shotguns.
BTW, do you know what the most popular weapon was on the late 19th Century Frontier; Colt six shooter? Winchester rifle? No it was the double barrled shot gun.
Is that right? Curious that the Militia Act of 1792 gave Militia members 6 months to acquire one.