Not much on specifics of history, butit seems that the .62cal(.20ga) is the single most commonly produced / used smoothboresize of yesteryear in general...a very versatile firearm.

They're as accurate as a rifle with patched balls to 50yds and almost as accurateat75yds...ranges that encompass 99.99% of all big game you'd want to use a 325grn lead ball for.
My Deer hunting loads:
80grns Goex 3F
.018" Oxyoke lubed pillow ticking
.600grn cast lead balls (from Eddie May in Georgia)


Shot loads are whatever you want/need them to be...just adjust the amount of powder and shot accordingly...for example, my Turkey Load is:
80grns Goex 3F
Two Oxyoke wonderwads
1+5/8oz #6s
Circle Fly OS card

A trap target loadfor the 16yd line is:
70grns Goex 3F
Two Oxyoke wonderwads
1oz #8s
Circle Fly OS card

You get the idea...smoothbores area wholedifferent area of muzzleloading to experiment with, learn about, hunt with, etc.