If you know what you want to build, you can't beat the AOP plans for detail. If you want to look at a variety of Civil War field cannons for inspiration for your next project, you can't beat the Hazlett book described below. It does contain dimensioned drawings for the Napoleon, but probably not as much detail as the AOP plans that DD mentioned (I don't have that particular set). I'm in the middle of writing up a set of mini-reviews for the cannon books in my small collection, which I'll post all together when I finish in a couple of days - here's my review for Hazlett:
Field Artillery Weapons of the Civil War (revised edition), by James C. Hazlett, Edwin Olmstead, and M. Hume Parks, 2004, University of Illinois Press, 324 pages, $25.39 (amazon.com) This is a very well organized book covering the smaller artillery of the Civil War, primarily covering weapons up to 12 pounder size, but also covering Coehorn mortars and a few larger weapons. Each chapter focuses on a specific type of cannon and has good descriptions of their design, construction, and use. There are many photographs of cannons in their current state in various parks. There are quite a few fully dimensioned drawings of barrels. Mountings are not covered well, but chapter 17 “Carriages” has some nice photos of a reproduction Napoleon carriage and its parts, as well as basic dimensions for some common field carriages. The appendixes contain locations for existing field weapons, which is a great way to find the nearest location for your favorite gun. You get a lot of bang for your buck with this book! There is a preview of this book at google books, so you can take a look and see what you will [size=0pt]g[/size]et before you buy.