<Snipped quote by Lauder>
<Snipped quote by Zugzwang>Yeah, 19th century tech is weird because it only picks up near the end.
Mid 19th century is basically almost like the Napoleonic era.
There are some distinct differences like gradual spread of breechloaders and the Minié Ball but that's quite a massive kick in tech.
1980s would most likely make more sense, IMO.
Eh the mid sixties is the end of the US civil war. Which means we have some brass, quality cannon that won't hange much for 30 years, and the first generation of breech-loading rifles.