Mr. Greens plans were published in some long discontinued Hobby Machinist Magazines as well as the early version of Home Shop Machinist. I have quite a few of his drawings and would like to find more.
Mr. Greens drawings are old school hand drawn and not CAD/CAM product. The are quite simple to use and make a good looking gun in the end.
Several years ago one of the fellows on this board made contact with Mr. Greens family and inquired about acquiring the rigths to Mr Greens plans. Before we heard a response, Jim died. about 4 years ago the folks at VillagePress the publishers HSM forwarded a letter I wrote asking about acquiring the rights to Mr. Greens plans. The letter was never responded to.
To night while doing some research I came across a website selling cannon plans The inventory look similar to William Greens.
Scale Model Civil War Cannons