Looks like it hit bone and tumbled and probably framed. In guessing the spine? Bone becomes projectiles and cam make come really big holes. That's not always the case and can't expect results like that although they do happen. I had a hole in a coyote I could stick a grapefruit in and still have an inch or two around the sides. But it was with my 260 and 120 gr a max normal exits were half dollar. This was huge because I shot it running at 250 yards and hit it in the hips blowing the bullet to pieces and the bones out the other ride as 2ndary projectiles. I didn't know it was possible to get a hole like that out of that gun ammo combo and had shot around 35 with it at that point. Had it been my first and only one I would have thought that 260 was like a 50bmg.
In my experience a bullet almost always hits bone. Almost always, especially in a coyote sized critter given the extensive penetration due to relatively small body size. I've dropped quite a few coyotes with fmj of various calibers. I suspect those who say they don't work, or don't work well enough, are often stating someone else's theory. I'm talking thin skinned pretty scrawny animal; ie coyote. I would not want to try plugging moose or elk w fmj bullets although I do load up w fmj 357 'bear spray'. There is likely better 357 bullets but we have some big bears and I hope to break some bone if it ever comes to that!
Sure it hits bones I ment heavy bone like the spine at an angle like the picture appears to show or like through the pelvis like the one I mentioned. I should have made that clear my mistake. A rib or to is not as big of an effect. Your right though I don't have much experience with fmj. Sure they can kill things but there are better bullets for that and I get enough spinning and flipping with explosive varmint bullets that do a lot of damage to avoid using anything less.
Infact I don't use a 223 anymore because I have results I like so much better with a 243 7mm08 and 260. Yes I can drop them with one shot from a .22lr at 65 yards but I don't like to limit myself. Others have different experiences , expectations, and priorities. Some want to shoot cheap, small holes in skins, and don't mind if they have to follow a blood trail if thing don't go perfect. I understand that. I prefer bang flop every time and I don't care if it's got a basket ball size hole in my $2 coyote. I load my ammo so it comparatively cheap and I only want to shoot one load out of each gun. So a 100 gr sp for deer will be what I shot a coyote with out of a 243 for example. Checks all my boxes.
Now a .223 with 45gr hp is a great gray squirrel round and when shot in the chest behind the shoulder no meat loss. They are so thin they don't open up but hit so hard the impact blows the guts out. Zero crawl offs I bet fmj would be about the same. Good for squirrel and you can limit out from 80 yards . Guess I can find a use for fmj.
I love 158gr Hornaday xtp in 357 out of a carbine and out of a pistol will get the job done. But I think I would carry my ruger 45lc with heavy 300gr hard cast Keith style bullets for back up bear protection. Back up for my 12g with rifled slugs. I used guns people said were to small all the time when I was younger at ranges people won't believe. Now I prefer bit bigger guns. Not stupid big I don't like heavy recoil but big enough.
I live in Indiana so no experience with bears or anything bigger than a whitetail. But I'm pretty sure I would want a big hole and very deep penetration. Figure I want to be sure it's dead don't want anyone putting them self in danger trying to kill a bear because it killed me. I would rather have the dead bear next to my body.