I built a number of varmint rifles and worked, part time, for a Gunsmith in Shreveport LA., when I was stationed there. Later I built quite a number of accurized 1911's and was seriously thinking about opening a gunsmith business when I retired.... Luckily, before I retired I calculated what expenses and income would be for a one man shop and discovered that it might well be better to take up pumping gas as a retirement job :-)
Re small bore, just before I left Shreveport I built a .17 cal (smokeless) wildcat rifle. I can't for the life of me remember what the cartridge was based on but it was a rimmed case necked down and fire-formed. I got a barrel from Douglas and built it up on a small Martini ,"Cadet" I think, action put really good wood on it and was real proud of it... Beautiful little gun and 3,000+ FPS loads, and it was a real tack driver... for the first two, maybe three, shots but I could never could shoot a 5 shot group that I was willing to show anyone :-)