I have broken more than my share of self bows over the years when the backs let go including Hickory, and White Oak, Black Locust,Elm, Horn beam, and Osage for one reason or another, but have never broken the back of a Walnut bow. Has to be wide to minimize set.Also has to be belly heat treated multiple times if made this short. The wood has to be knot free which this one is. The growth ring for the back will be very thick. It is a low mass wood, and soft , so it will ding easily. I took this all in to account by design when I built the bow. Good shooting, and hunting.