Hunting with a 5.56 is legal in most U.S. states, but the details decide everything. The majority of states require only a centerfire cartridge for big game, which lets the 5.56/.223 through. Roughly a dozen states set a minimum caliber (commonly .24) or a minimum energy figure that shuts it out for deer. Where it is legal, the cartridge is excellent on varmints and predators and sits at the bare minimum for deer, so ammunition choice, shot distance, and shot placement do the heavy lifting.
Is 5.56 Legal for Big Game in Your State?
State rules fall into three groups. The most permissive require only a centerfire cartridge with no minimum bullet diameter, which allows 5.56/.223 for deer. A second group sets a minimum caliber floor, often .24 caliber (6mm), which excludes the 5.56’s .224-inch bullet. A third group imposes a minimum muzzle or impact energy, sometimes combined with a cartridge-length rule. Check your state wildlife agency’s current regulations before you plan a hunt. A wrong assumption here can turn a legal outing into a criminal violation.
Two other rules apply almost everywhere. Most states require expanding ammunition for big game, meaning soft-point, hollow-point, or polymer-tipped bullets. Full metal jacket rounds, the cheap bulk ammunition sold for target shooting, are prohibited for hunting in the vast majority of states, and using them on game is widely considered unethical even where no explicit ban exists. FMJ bullets punch through tissue without expanding, transferring little energy and wounding rather than killing.
If you hunt with an AR-15 or another semi-automatic rifle, watch magazine capacity. Several states cap hunting magazines at five or six rounds even when larger magazines are otherwise legal in the state. A standard 30-round AR magazine that is perfectly legal at the range can be illegal in the field. Swap to a reduced-capacity magazine before season; forgetting can mean fines, license revocation, or both.
Choosing Hunting Ammunition for 5.56
Ammunition selection is where the 5.56 either becomes a viable hunting round or a way to wound animals. Military-surplus FMJ loads are cheap and abundant, which is why hunters keep making the mistake of grabbing them. Those bullets are built to hold together, not expand, so you get a narrow wound channel, poor energy transfer, and animals that run off hit but not killed.
Expanding Bullet Types
Soft-point and hollow-point bullets have been the hunting standard for decades. They expose or weaken the lead core at the tip so the bullet deforms on impact, widening the wound channel and dumping energy into vital tissue. Polymer-tipped (ballistic tip) bullets add a plastic insert that improves aerodynamics and drives back into the core on impact to initiate expansion.
For the 5.56 in particular, bonded and monolithic copper bullets deserve extra attention. Bonded bullets lock the jacket to the core, preventing the separation that can plague standard cup-and-core designs at high velocity. Monolithic copper bullets are one solid piece of copper alloy, with no jacket-core interface to fail. They retain nearly all their weight through impact, expand reliably, and track straight. With the 5.56’s limited energy budget, every grain of retained weight matters for reaching vital organs.
Bullet Weight for the Animal
For varmints and predators, standard 55-grain hunting loads work well. The lighter bullet expands or fragments rapidly at 5.56 velocities, which is ideal for coyote-sized animals and smaller. For deer-sized game, bullets in the 62 to 77-grain range are a better match. Heavier projectiles carry more momentum, penetrate deeper, and hold together better against bone. A 55-grain varmint bullet on a deer can come apart too early and fail to reach vitals, especially on a quartering shot.
.223 Remington and 5.56 NATO Are Not Interchangeable
The terms get used as if they mean the same thing, and they don’t. The 5.56 NATO round operates at roughly 58,000 PSI; the .223 Remington is loaded to about 55,000 PSI. Fire a 5.56 NATO cartridge in a rifle chambered exclusively for .223 Remington and the shorter throat can push pressures to approximately 65,000 PSI, about 10,000 PSI above the .223 Remington’s rated maximum. That overpressure can blow primers, damage the rifle, or injure the shooter.1Hornady. What Is the Difference Between 5.56 NATO and 223 Rem Ammunition
The reverse is always safe. .223 Remington ammunition fires without issue in a 5.56 NATO chamber. Many modern sporting rifles are chambered in .223 Wylde, a hybrid design that safely handles both cartridges while keeping good accuracy with either.2Faxon Firearms. The Definitive Guide to Understanding 223 Wylde Confirm your rifle’s chamber marking before buying ammunition. It is stamped on the barrel and listed in the owner’s manual. If the rifle says “.223 Rem” only, stick with .223 Remington ammunition or have the barrel re-chambered.
Barrel Twist Rate and Bullet Weight
Twist rate determines which bullet weights your barrel can stabilize. An unstable bullet wobbles or tumbles (keyholing), which destroys accuracy and prevents the bullet from expanding as designed on impact. That directly affects whether your shot kills cleanly or wounds.
Most AR-15s and modern sporting rifles in 5.56 come with a 1:7″ or 1:8″ twist, which stabilizes the full range of available bullet weights. Older rifles or some bolt-action .223 hunting rifles have a 1:10″ or 1:12″ twist. Those handle 55-grain bullets fine but struggle with the heavier 75 to 77-grain hunting loads that perform best on deer. A 1:10″ twist generally caps you at 69 grains or lighter. A 1:9″ twist handles up to 77 grains adequately, and a 1:8″ or faster is optimal for the heaviest 5.56 projectiles. Confirm your twist before you buy premium hunting ammunition.
What Game the 5.56 Handles Well
Varmints and Predators
This is where the 5.56 genuinely excels. Coyotes, groundhogs, prairie dogs, and similar animals are well within the cartridge’s capability. High velocity and a flat trajectory make hits easier at moderate range, and even a 55-grain expanding bullet delivers far more energy than these animals need for a quick kill. Most experienced hunters consider the 5.56 one of the best varmint cartridges available.
Deer
Deer hunting with the 5.56 is where the debate gets heated. The cartridge can kill deer cleanly, but the margin for error is razor-thin compared with a .308 Winchester or .30-06. A 62-grain 5.56 bullet from a 16-inch barrel carries about 1,213 foot-pounds of energy at the muzzle, roughly 1,004 foot-pounds at 100 yards, and 820 foot-pounds at 200 yards. Many hunters treat 1,000 foot-pounds as a reasonable minimum for deer, which puts the 5.56 at the threshold at 100 yards and below it at 200. Heavier 77-grain loads stretch this slightly, carrying about 1,121 foot-pounds at 100 yards, but still drop under 1,000 before 200 yards.
The practical rule: keep shots inside 150 yards, use the heaviest expanding bullet your barrel stabilizes, and take only broadside or slightly quartering shots placed directly behind the front shoulder. A perfect double-lung hit will kill a deer with this cartridge. A marginal shot (too far back, too steep an angle, or too long a range) is far more likely to wound than it would be with a larger caliber. If you can’t guarantee the shot, don’t take it.
Feral Hogs
Hogs occupy an interesting space. Many states classify them as invasive nongame animals with few or no restrictions on caliber, method, or season, which makes them technically fair game for the 5.56 even in states that restrict the cartridge for deer. The problem is practical. Hogs are built tough. A thick shield of cartilage and tissue covers their shoulders, and their skulls are angled in a way that can deflect marginal shots. Hunters who use 5.56 on hogs consistently report that head and neck shots drop them quickly, while body shots often result in hogs running 75 yards or more, frequently into dense brush where tracking is difficult or impossible. On boars over 150 pounds, the cartridge’s limitations show. Many hog hunters who started with 5.56 eventually move to larger calibers like the 6.5 Grendel or .308 after losing too many animals to insufficient penetration.
Shot Placement Carries the Cartridge
Placement matters with every rifle, but with the 5.56 it is the single factor that separates a clean kill from a wounded animal. Larger calibers give you some forgiveness; a .308 that lands a few inches off still transfers enough energy to be lethal. The 5.56 does not offer that cushion.
On a broadside deer, aim directly behind the front shoulder, about one-third of the way up from the bottom of the chest. That puts the bullet through both lungs, and a deer hit through both lungs rarely travels more than 35 to 125 yards before expiring. Slightly forward catches the major arteries feeding the heart and often drops the animal on the spot. Too far back hits the liver or gut, a wound that will eventually kill the deer but may take hours, with the animal traveling far enough that you never recover it. Head shots are instantly lethal when they connect with the brain, but the brain on a deer is roughly the size of a baseball, and a slight miss destroys the jaw or nose and leaves the animal alive and suffering. Stick with the double-lung shot unless you are at very close range with a rock-solid rest.
Penalties for Hunting With the Wrong Setup
Using a prohibited caliber, illegal ammunition, or an oversized magazine while hunting is not a slap on the wrist. Depending on the state, violations can be charged as misdemeanors carrying fines, jail time, mandatory license revocation, and disqualification from future hunting privileges. Serious or repeat violations escalate to felony charges in some states. Game wardens do not need probable cause to check your equipment in the field; consenting to inspection is a condition of holding a hunting license in most states.
The cost extends beyond fines. Many states share violation data through interstate wildlife compacts, so a revoked license in one state can block you from hunting in others. Regulations change from year to year. Read your state wildlife agency’s current rules before every season.