The general WT deer season has been open in BC since Sept 10. Notsorichguy, you need to get out more often.
When a highly frangible bullet comes into contact with a rib, especially at higher velocities, it does a lot of damage. Those littel pieces each take a bit of impact pressure with them. In some cases, especially with heavier bullets, they will cause the rib to bend and tear the muscles around it when they are first hit.
I was looking for the video is saw that was done on bullet impacts on beef/sheep/goat ribs with high speed cameras. They did tests with everything from solids to extremely frangible hollow point lead tipped bullets at different velocities. I couldn't find it. I know it's out there, I just don't emember where to look for it.