No idea what rules and regulations are like, downunder, but if permissible, you might do both.
Start with the much shorter length of a handgun barrel- "average" not snub or Buntline.
Major diff is only in the length, work takes about 1/3 the time on the shorter length, so all relevant techniques can be mastered with fewer hours and fewer tears if you have to scrap something.
No, it doesn't resolve the long drill, ream, broach/cut/button issue, but it covers all the basics - boring, rifling, chambering - whilst you 'sess out and improve your skills and familiarize with the capacity of your machinery. Single shot actions are not hard. Duplicating a barrel for an existing handgun, OK, too.
Doesn't even HAVE to be smokeless powder, does it? Walk first, gallop later.
2CW