Update on a work in progress: my friend’s SF novel from the 80s

My friend Duncan was perhaps not really a polymath, but even back in high school he was something in that direction. He was interested in the history of firearms. As luck would have it, there was a shop in our area of University Park (one of the wealthy enclaves within the city of Dallas known as the Park Cities) that specialized in such things, a place called Jackson Arms, which he visited often; he owned an antique that, as I recall, he identified as a matchlock, rather than a flintlock, ri...