Finally took time to watch the video. Cool seeing the Gatling firing.
And like your Gatling models, well done. Not quite sure what model your artillery are - perhaps the 3.2" guns shown in the video? I believe more common in the Custer era were 12# and mountain howitzers but your guns will work.
Oh, and book I am reading identifies the Gatling gun's in Terry's column as being manned with personnel from the 18th infantry.