Not arguing with you Mike You made some very good points. Lincoln did preoare it earlier and could have released the Emancipation Proclamation earlier, but he wanted a victory first. The EP politically changed the originally course of the war from preserving the Union. A lot of democrats would have been upset. The victory placated them and made it more acceptable.
Back on topic of a full automatic Civil War weapon so devastating that its mere presence would cause the opposition to sue for peace. A simple cartridge could have been like the early Gatling cartridges - almost bored through metal tubes with recessed nipple so as to keep it tubular. They could easily be reloaded and in a steam power Ager Coffee Mill gun it would have worked. A water driller could reduce the fouling as it fired.
Gee, if I go to gunsmithing school, I wonder if they will let me do this as a school project?