While out doing some test loads for my 6.5 creedmoor today, I was able to recover quite a few of my bullets to see how they expanded. While looking for mine, I found this one in the picture below. It looks like it is a .224”. What would cause this flattening behind the cannelure? It went through some OSB target backer and into the dirt. I also found a .308” bullet that looked the same, flattened behind the ogive of the bullet. Were they tumbling after they went through the OSB?