The current ammo and animal classifications are better than it was in the early days of cotw and isn't terrible imo, but mistakes were made. I am a hunter irl and have experience with a vast variety of cartridges and their performance on various game animals so here's my take, feel free to include any of your thoughts. I am only listing the classes that I feel need changed, not the performance of the ammunition. Ammo changes are based on real world caliber minimums/restrictions and what is typically used and considered a good choice for sport hunting and not survival hunting (why I'm not making 243 class 8)
ANIMAL CLASS CHANGES
Class 3: Move Axis deer and Pronghorn to class 4
Class 6: Move Red Deer and Gemsbok to class 7
Class 7: Move Eurasian Brown bear to class 8
Class 9: Move European and Plains Bison to class 8
AMMO CLASS CHANGES
.270 3-8 from 4-8
.300 magnum 6-8 from 7-9
.303 british 3-8 from 4-8
.308 3-8 from 4-8
.338 magnum 6-9 from 7-9
.375 magnum 6-9 from 7-9
.45-70 3-8 from 4-9 (currently insufficient for class 9)
.450 3-7 from 4-7
.470 Nitro Express 8-9 from 9
6.5mm 3-7 from 4-8
7mm magnum 4-8 from 4-9
7.62x35* 2-6 from 3-6
9.3x74r 6-9 from 5-9
*.300 blackout, might have gotten the in game designation incorrect since the wiki doesn't list it and I'm not 100% sure of what it is in game.
EXPLANATIONS
Axis and Pronghorn are nearly identical in size to whitetail and anything someone would use for whitetail, is typically what would be used for these two.
Red Deer and Gemsbok are very similar in size and toughness to an American elk and are hunted many times with a 30 caliber magnum.
The Brown Bear and Grizzly are extremely close cousins, think whitetail and coues deer here in North America.
Both bison species are not as tough as the african cape buffalo or asiatic water buffalo and typically have a lower minimum caliber than the other class 9 animals.
Weapon explanations on request (It is getting long) Again please share your thoughts and opinions.