Well, in the spirit of, "every little helps"...someone above suggested that this could be written in Kanji, and it could be- but it isn't showing any of the telltale Japanese characters I'm familiar with. Though I don't speak Japanese I do know a little bit of Chinese, and the language stamped on this weapon appears to be Chinese in my opinion.
If so, (translated into pin yin) the characters on the barrel in photograph one appearing beneath the flower insignia read:
mu - tree or wood (you have this as 6 from somewhere- that looks like an error to me)
qi - 7
si - 4
qi - 7
fan - kind or type, but this fan character is the first half of the the binary character "fan hao:" defined by my trusty Oxford as "designation for a military unit," and a tendency to leave off the second character when the meaning is "obvious" is one of the things that endears Chinese to foreign learners.
So that could well be a unit designation of some sort. As far as that stunning insignia, I think I've ruled out the 8 Banner Armies which were my first thought, but as stated above there are plenty of other options. China was a hodgepodge of military units after the mid-nineteenth century, and the poor quality of locally produced munitions meant that frontloading arms remained in use there far later than say Japan, so that Chinese soldiers could visually inspect the quality of the powder.
I've had a go at the second group of characters you posted in photograph six, but the last few are indecipherable- hard to tell what's character and what's woodgrain. They are obviously older, written before the communists simplified the language (no surprise), but it would probably be easier for someone at your end with some Chinese language background to try to work them out. Try to find someone with some gray in their hair- younger people probably won't be able to read the pre-simplified material. At the least, if you could rotate photo six 180 degrees, it would keep me (and hopefully others) from having to turn our heads so much :wink:
Hope this helps!
Boomer