Nah @the_hugo you're missing how smart those barrels actually are.

Cameron's point about dry oak having internal stress is spot on. That brittleness means the wood can fracture along hidden weak points, no matter how careful you drill. One thing that helps is to drill a pilot hole, then gradually step up the bit size before the final screw. Another tip is to rub a little soap on the screw threads to cut down on friction when driving it in.

Wow, my buddy learned that the hard way when his hammock anchors pulled loose on a camping trip. He just didn't leave enough give for the smaller trees to move.