How to Plug Barrel Rounds
Knock plug out of barrel round.
Spread wood glue generously around the plug.
Spread wood glue inside the hole as well.
Fit the plug into the hole and give it a quick tape with hammer. Don't overdo it or the round will crack.
Stack so that corks are not overlapping.
Once dry (>3 hours), clamp the round to the table and cut flush with reciprocating saw.