While I know absolutely nothing whatsoever about this particular war, I have a thought concerning breech loading artillery.

After the American Civil War the US Army produced only a few guns until around 1900, but in that interim period many of the guns looked a lot like the 12 pound Napoleon, but with an opening breech rather than the closed breech and no cascabel, that's the knob on the breech end.

So I have taken some of my surplus ACW guns and cut the knob off the end and painted them as if they were 1880's artillery and solved the problem using existing equipment.

https://bunkermeister.blogspot.com/2017/08/dr-dooms-army.html

Here I was making an army for Doctor Doom, he is the prince of Latveria and that country has a small and under equipped army.

I took an ACW 12 pounder Napoleon, and pierced the bell on the breech end and pushed a rod through it. That turned it into a breech loader with the rod being the handle to open the breech. I also updated it to the 1930s or so by adding rubber tires. But by leaving the original wooden spoked wheels you could make it an 1880ish gun, in my opinion.

Close enough, is good enough unless they make exactly what you want.

https://bunkermeister.blogspot.com/2017/08/the-army-of-latveria.html

Here are some more views of the cannon, I made four of them.

Hope that helps.

Bunkermeister