Does anyone here have anything substantive to add to the notion of gain twist? I have been asking around and reading and talking to one barrel maker about it, and there is nothing definitive. Best I can find is that most British BPE gun makers 1850-1900 used gain twist rifling, as well as tapered bores. Charles Lancaster was a big believer in gain twist and he used it in his successful oval bore cannons.
I ask because I am in the beginning stage of building a percussion rifle. Colerain makes gain twist barrels, and they will make one for this project, if asked.
Thanks!