There are a lot of different cartridges out there, and there is a reason why your favorite cartridge is your favorite. Each different cartridge was engineered with a lot of consideration. Everything from the dimensions, or size and shape of the cartridge, to the size of the bullet and the amount of gunpowder. There are reasons behind those decisions, just as there are a lot of different reasons to shoot those cartridges. The makers of every cartridge will often project an intention of some kind that influences the design of the cartridge. From military applications to self-defense, match shooting to hunting there are a lot of ways to use these respective cartridges. Some that were created with one application in mind found a large following in another because they excelled at it. Regardless of why a particular cartridge was created, there are some that excel at hunting. But using one cartridge to hunt everything would be like using one cartridge for self-defense, match shooting, and military applications. After all, with a shoe you could protect your foot, hammer a nail, remotely turn off your light, or open a bottle of wine. You can make all of these work, but why would you when there are other, better tools for the job
     A general and probably obvious rule when it comes to hunting is: the bullet size will be proportional to the size of the game, the bigger the game, the bigger the bullet. Bigger bullets tend to be found in bigger cartridges which tend to be bigger calibers. That said, there are many different cartridge types with different bullet sizes or load characteristics within a certain caliber type cartridge. So with that in mind, let’s look at some of the more popular cartridges and the game they were intended for. There may be a few of these that you don’t see too often on the AR platform, however, most are possible. 
     Starting small, we have the many iterations of the .22. The very popular .22LR, the .22LMR, and the .22 Hornet are all good for varmint hunting and the LR and LMR are great for small game. The .223 REM is a high-velocity round of similar size of the .22, and is great for varmints, small game, and does well against smaller predators like foxes or even wolves. Other larger cartridges excel at predator hunting like the .22 Nosler, .224 Valkrie, .220 Swift, and .243 WIN. .243 WIN is good for hunting deer at short distances, and so is the .300 Savage which can also work for smaller black bears. With the 6.5 Grendel, 6.8 SPC, .270 WIN, .308 WIN, 30-06 Springfield we’re definitely getting into the bigger game here. Deer? No problem. Sheep and goat? Should go without saying. Bear, wild hogs, even large elk? Yes. The .300 WIN Mag (Winchester Magnum) is where you can start getting into the much bigger game like grizzly and moose, while other great cartridges include the .300 WBV (Weatherby Magnum), .338 WIN Mag (Winchester Magnum), and the .375 Holland & Holland. If you are required to use straightwall cartridges by law where you are hunting there are some decent choices for you. The .350 Legend and the .450 Bushmaster are two straightwall cartridges that will definitely work for deer hunting and the .450 Bushmaster can be used on moose, elk, and bear. Finally for the really big game 6.5 Creedmoor, and the 45-70 Government top out this particular list of cartridges. 

Cartridges & Their Common Hunting Applications:

- .204 Ruger - Varmints, Small Game 
- .22 Hornet - Varmints, Small Game 
- .22 Nosler - Varmints, Small game 
- .220 Swift - Varmints, Predators 
- .223 Remington - Varmints, Small Hogs and Deer 
- 5.56 NATO - Small game, Predators, Deer 
- .224 Valkyrie - Hogs, Deer, Pronghorn 
- .243 Winchester - Deer 
- 6.5 Grendel - Deer, Wild Hogs, Bear, Elk 
- 6.8 SPC - Deer, Wild Hogs, Bear, Elk 
- .270 Winchester - Deer, Bear, Wild Hogs, Elk, 
- .300 Blackout - Deer, Wild Hogs 
- .308 Winchester - Deer, Pronghorn, Bear, Elk, Moose 
- .338 Winchester - Deer, Bear, Elk, Moose 
- 6.5 Creedmoor - Large Game 
- 45-70 Government - Large Game 
- .350 Legend (Straightwall) - Deer, hogs 
- .450 Bushmaster (Straightwall) - Deer, Bear, Elk, Moose