There
was one other thing that looked off, but I forgot about it once I started looking at the figure himself.
It's that the Colt Army 1860 appeared to be enormous, and is actually longer than the Walkers.
The 1860 in real life is 355.6mm long (14"). Sideshow's is 68mm long: i.e., 408mm / 16". (Damn! What happened, Sideshow?)
On the other hand the Walkers are 66mm and are pretty much spot on converted to 396mm. (A real Walker is 390mm).
Half of the problem comes from the barrel length. Sideshow made them both 38mm (i.e., 228mm / 9").
The Walker's barrel is 230mm long, so again spot on.
The standard 1860 barrel length is 203.2mm / 8".
It's a shame because the mould and paint are good, but it's nearer to 1/5 scale in terms of length and looks ridiculous pushed into his belt.