Having just joined, I'll say hello to the group. I am a retired computer systems engineer and one of my hobbies is my home machine shop, where I recently finished restoring a 75-year old metal lathe.
 Now for a project that will use it and my other metalworking tools: I plan to scratch-build a detailed model of the French 75 mm Canon de 1879, (or its American copy, the M1879.) I look forward to sharing my progress and problems here. What scale and how detailed?. Current guess is somewhere between 1:10 and 1:5, and as detailed as my information, skill and tools permit.
Why did I select this particular weapon? Another hobby of mine is family history (genealogy), and I have researched my grandfather's participation in an historic event of WW I. He was a lieutenant with the AEF's  Battery C of the 6th Field Artillery. And it was this battery that fired the very first American shots of the war, on 23 Oct 1917. The project is in his honor.
I served in the US Navy on attack submarines in the 1970's, so I'm not an expert on artillery. (Ask me about torpedo fire control.) Â I hope to tap this group's knowledge and resources.Â
Welcome aboard! It's always nice to have a squid or two on the roster . . .  (I served on COMSUBDEVRON 12 staff from '78 to'83, so have some good memories about submariners.)  You might want to check out the Joe Martin Museum and Machine Shop Facility in Carlsbad, CA . . . . http://www.craftsmanshipmuseum.com/facility.htm. Not sure if they have any '75s there, but they have about everything else. Would think that the manuals posted on this site today could be most helpful.
 That Craftsmanship museum was what sparked my interest in machining! I'd done the standard metal shop stuff in high school, but hadn't touched the stuff for 40+ years. After getting a lathe and mill, my first big project was a single-cylinder, 4-stroke engine.Â
I've been to the Craftsmanship Museum about 6 times now, it's about 12 miles from home. I was there just a week ago, specifically to look at their weapons collection and check their library. Nothing really applicable to my project. I am hoping that perhaps the results of my cannon effort might find a home there.