I became interested in Italian reproduction Civil War-era black powder "Percussion/Cap & Ball" revolvers back in the late 1970's. You can buy them in most US states mail-order because there are no federal restrictions on them. They are considered antique firearms so no background check is needed. They are a lot of fun but totally impractical for defense by today's standards.
It takes several minutes to load them and they are not reliable. Misfires & jams (due to pieces of spent caps falling into the action) are an issue. When they came out in the mid 1840s they were state-of-the-art and gave one the ability to get off multiple shots very quickly at a time when almost all pistols and rifles were single shot muzzle loaders. These are my 3 guns and they were the most coveted percussion revolver models 155 years ago: