The submachine gun on the other hand? The materials needed to build them are already there in 1861. Got cartridges? Check. Got plumbing parts? Check. Got metallurgy knowledge and guys who know how to operate machine tools? Check.
Indoor plumbing was as rare in 1861 as 1980's cell phones.
In much of the south, the "local hardware store" was not really very local, and contained very little hardware other than nails, hinges, and other GP goods that could be mass produced easier than the local blacksmith could make them.
For pete's sake, you are talking about widespread use of milled interchangable parts, when the 99% of the population was still using a chamber pot or the "back house" .....
The wheels of technology turn slowly, indeed ......
Less than 70 years ago, my mother lived on a largely self sufficient farm that had a handpump in the kitchen sink, new electric lights, a woodstove for heat ..... and there was an outhouse out back. Just because there were A-Bombs being made in Oak Ridge TN at the time does not mean that modern tech was ubiquitous, or even common, in rural America.