A great source of info about the early days of punt guns is Col. Peter Hawker's "Instructions to Young Sportsmen". Even more so - Hawker's diaries, where he describes not just his experience punt gunning, but also his dealings with Joe Manton, John Manton, Charles Lancaster, Durs Egg, and other gunmakers of the day. Both books can be freely downloaded from www.archive.org (downloading tip: don't jump on the first title that comes up in your search - look for large sized versions digitized by a university, they'll have recognized text and higher quality drawings).