From what I've read, the lever-action repeating rifle design didn't really take off before the 1850s, but a design was created and patented in 1848. Though, it never made it into production. What becomes unclear to me is whether the improved version of the 1848 design made it into widespread use. The improved version being made by Lewis Jennings, that, according to Wikipedia, was not only built, but also sold. My question is, was this version (1849) widely used in the U.S., and if so, available to the average Joe or more reserved for law enforcement and/or richer types?
The functioning of any magazine-fed breechloading rifle was, really, dependent on metallic cartridges. The early Volcanic lever-action might seem to be the equivalent, but it was quite under-powered- the entire powder charge was contained in the hollow base of the bullet: and that was of course black powder, not smokeless!. Even though it was produced by the skillful Robbins and Lawrence shop, there were constant problems with it working well.
In the 1850's there were various designs for metallic cartridges tried. Rimfire was the easiest to produce ( .22 Short appeared then, the longest-lived of any cartridge) , and going into the 1860's and the Civil war, a number of guns like the Spencer and Henry rifles used large caliber short-case rimfire cartridges. .In the early "balloon-style" case designs, though, cartridges were sometimes difficult to extract without shredding, once the gun had gotten fouled after several shots, and centerfire cases were stronger in this regard than rimfire cartridges. For higher power cartridges, therefore, centerfire eventually became standard.
As far as who would own these guns: anyone who shot a repeater would have to buy loaded ammunition- it could be reloaded, yes, but it was still another item to purchase. For this reason, the truly penurious and poor would often still be using muzzle-loading guns for hunting in the late 1800's and even into the 20th c., especially in places like southern Appalachia.