3 AR-15s for 3 Types of Game

The AR-15 has become one of the most popular firearms in America, mostly due to its versatility, ease of use, and military look. It has even been adopted by hunters, who have embraced the AR as their rifle of choice in the field.
There are subtle differences as to how to best optimize your AR-15 for game of all sizes. Here's what you need to know.
Small Game

Rabbits, squirrels, and prairie dogs are some of the most common small game targets for hunters. The caveat with hunting smaller animals with an AR-15 is that you must have superior aim, and if you plan on eating your small game, the AR is not ideal for the takedown.
Many AR-15s come with 1:9 twist barrels, meaning the bullet spins one full rotation per nine inches traveled in the barrel. Most Remington .223 cartridges are 55-grain, and the 1:9 twist rate is ideal for maximum efficiency and stabilization with said cartridges versus 1:12 (slower) and 1:7 (faster). AR-15 barrels, like all parts of the rifle, are easy to replace and switching takes only minutes.
Your optics should also be made specifically for small game, paying close attention to clarity and resolution at less than 100 yards. A 4-12X40 variable scope is recommended for small game.
Varmints

Whether it's coyotes, javelina, or wild hogs, many jurisdictions not only allow but encourage hunters to take down varmints in the area. Hunting varmints require different hunting techniques than small game, so a few items must be considered to properly set up your rifle for these endeavors.
Most AR-15s specifically built for hunting nuisance animals have longer barrels and slower rifling—a typical stationary shooting setup. The longer barrel provides better velocity and range, perfect for animals 200 yards away or further. ARs for these animals are typically heavier than those built for small game, so you may need to experiment with different stocks for comfort. Some hunters prefer collapsible stocks and add cheek rests to them, while others like fixed stock styles.
Suppressors (silencers) are also a popular addition to AR-15s for varmint hunting, since you can potentially hit the target with a second shot if you miss on the first. Keep in mind, a “silenced” AR-15 is a relative term—it's not like the silencers in the movies.
Large Game

The upper receiver ultimately determines whether your AR-15 is built for small or large game. The standard .223/5.56 rounds are not ideal for large animals, but a simple switch to a larger caliber will work.Though more expensive and heavier, the AR-10 setup is ideal for deer hunting.
You can also simply buy an AR-15 already built for large game hunting, like the Ruger SR-762 and YHM HRC-200 6.8 SPC.
The best part about owning an AR-15 is that it's never a finished product. You can always modify it with different parts and accessories for any hunting and target shooting activities.
Legalities
There is no federal law controlling the use of the rifle, though many states have regulations on citizens' rights to purchase, own, and use it. According to TIME Magazine, AR-15s are used for hunting in several states, including hunting feral goats in Hawaii, feral pigs in Texas, jackrabbits in Arizona, and elk in Montana. Some states don't allow deer hunting with .223 diameter bullets or an AR-15 rifle, according to Stag Arms. These states, including Colorado, Connecticut, Illinois, Iowa and Massachusetts, require larger bullets. Many states have laws for hunting specific game with specific types of guns and ammunition, so it's best to check your state's current laws before heading out on a hunt.