A few years back up at ShrewHaven, I purposely killed 2 does, one with a cedar shaft, the other with carbon. They were almost identical in size, and body angle. I was in the same tree, and hit them in about the same spot, double lung. I used the same broadhead, a Magnus 2 blade. I do not remember arrow weight, but they were almost identical, I was shooting them out of the same bow.
Both arrows completely penetrated. The carbon stuck in the dirt, the cedar shaft broke on a sapling.