I'm going to second the draw filing.
But not the info that a wooden block rounds over the edges.
For metal working, my blocks are maple. They are hard as a rock. But they won't harm the metal if I bang it against it accidentally. Your barrel would qualify for that safety.
For woodworking, I generally use softer woods to avoid dinging the wood if I bang against it accidentally and they have cork or felt bottoms, mostly cork.. The felt would round the edges, the cork might. And for your hex, that might be a good thing as a final easing of the edges.