I had a double rifle drilling with the shotgun barrel being a 32 ga. I bought a couple boxes of shells over time. I also had an insert so that I could shoot .410 shells. I understand that the 32 ga was somewhat popular in Italy and maybe France.

I have heard of a 36 ga but never seen a gun in that ga and wonder how different thatwas from a .410.

Another shell is the 9mm shotshell which is still being made. A friend had a gun in 9mm RF that he inherited. He also had some shells with solid ball. I have seen cane guns in 9mm RF shot. I think the 9mm RF shotshell was for shooting garden pest (squirrels, chipmunks, birds) that were eating one's crop. I think they are fairly quite and have a short range. Shot sizes range from #6 to #9 and velocity is about 600fps (I believe).

I think a cane gun in 9mm shot would be interesting to have.

On the other side of 9mm shotshells, there was a 2 bore which I would like to watch someone shoot; I wouldn't want to shoot a 2 bore. I like my shoulder where it is.