For informational purposes.
The Napoleon barrel I use is 27% size of the original full scale barrel.
The Napoleon was mounted on a #2 field carriage as opposed to the lighter Parrott and Ordnance barrels which were mounted on a #1 carriage.
The drawings for the #2 carriage can be found here (picture attached).
Every single piece that makes up the entire carriage can be found in these drawings. I took every drawing and scaled it down to 27%.
I made my own 27% drawings for every piece.
That makes the scale of my gun carriage as close to perfect as I can make it.
At 27%, there are a few very small metal pieces that I had to customize so they would fit. But there are not many.
The drawings can be found here.
Catalog #20 for the #2 carriage.
http://gunneyg.info/html/AOPCatalog.htm
The rest of it is only your willingness to put in the time. A few tools help also.
Barrel and wheels are fairly costly.
End product is a magnificent piece of artwork!