I would like to build a .62 cal smoothbore that can be used for both shot and patched round ball. Any comments/suggestions/advice on how barrel length may affect the handling/accuracy of the gun in each situation (shot vis-a-vie PRB) and what might be a good compromise length?
What time frame will the gun be? Early means longer later, 19th c especially, means shorter.
Improvements in powder, breaching and shot making in the mid-late 18th c all had an effect on barrel length I think.
A RB does not need a particularly long barrel and short barreled rifles were in use in Europe and England long before the fowling piece barrels shortened.
If you really want to confuse yourself look up “The Gun” By W Greener (not his son W.W.), 1835 and look at the things the British makers did trying to get better patterns and longer range kills.
Then we have George in “English Guns and Rifles”