Perspective is hard.
Circles are hard.
Thus, cylinders (esp. tyre treads!) are murder.
This puts more pressure on storytelling to carry the pic.
Happily, the client for this one (an actual artillery person) liked the result.
Despite this field piece being a fanciful melange spanning several wars,
I was happy with the shells, observation slits, metal fixings, and characters.
[Biro on paper (as study for t-shirt), circa 1995.]