damn that's a nice barrel
How did you get the holes to be such a nice shape? I've always wondered how to do that and boolean screws over my mesh
What I did was take a 8 sided cylinder, and extruded it inside a bit, then I took 6 sided cylinders and rotated them at a 45 degree angle like this

Then I'd have them as a separate object, add modifier, boolean, and set its operation to union.

Then I apply and delete the cylinders in edit mode


Then I ctrl+f the holes it made, and the result is a clean mesh. Their is probably a better way to do this but this is what I did.