A few things really need to change. Specifically how the ammo works in the game considering the changes and new items available.
First is the worst and most obvious problem, **every single base game or early dlc caliber is massively underpowered **. This game has had 5 years of progression and the ammo hasn't been changed to reflect that. Base game calibers are so far behind it makes dlc weapons almost necessary to enjoy the game. Particularly the issue is in weapons like the .45-70, .30-30, 7mm, .338, and .270, but the .30-06 seems to be a little weak as well compared to when it was released. All of them need an update to make them competitive to more recent DLC, I'm meaning penetration and bleeding effects.
Second, A ton of suggestions are calling for class changes and some weapons particularly need them. The most popular choices for 3-7 class animals are the .270, 6.5, and .30-30 all of these are used regularly for larger animals like black bear and alligator and they should be just as useful as the 7.62x54. Next is the issue of 4-9 weapons currently the 7mm is the only weapon that's really effective in this range but the .300 is widely used by hunters after kudu and deer (all species). The .338 and .45-70 should be exclusively 7-9, and they should be very effective at penetration with animals like bison and buffalo.
Third, the range restrictions on the .45-70 and .30-30 should be removed. They are both effective and can be easily sighted in at 300 meters, particularly with premium ammo they can do what any other rifle can and sometimes do it better. The Moradi .44 has already become a fast favorite and its a pistol cartridge outperforming the rifle cartridges in the same type of action which is ridiculous
Fourth, birdshot still needs a good boost OR a second type of birdshot (like the 20ga's steel shot) that is labeled and better to take on Geese and turkeys snce they are larger birds.