I'm intrigued by this whole idea.
What if you ripped all you staves on the table saw including the miter angle. then, cut the outside curve on the CW.
Made a sled with a matching curve in it. and carved the inside of the staves.
Do your end cuts with a jig in the miter saw or on a table saw sled.
Strap the barrel staves together with a ratchet strap and rout a groove around the inside to rabbet the barrel head into.
Then I think you will have to slowly dry your staves in the oven to get the MC as low as possible before you put on your barrel bands.
Jeez...... this is starting to sound like a lot of work
I don't know if you planned to make it an exact replica of a full size barrel