We seldom pay much attention to a gun carriage's relationship with its mount...so here ya go! Smaller iron wheels rotate directly around the mount's pintle in the center, and larger wheels roll along the flat iron bands further out...at least they should do so, looks like there's one wheel too many off the rails! Does that mean this is the improper carriage for this mount, or did they just not care about that furthest wheel out there? I do not pretend to be any sort of artillery expert, I only pretend to be a starfort expert.