What Calibers Are Legal for Deer Hunting in Wisconsin?

Any firearm used to hunt deer in Wisconsin must be at least .22 caliber and fire a single projectile designed to expand on impact. That baseline covers the legal calibers for deer hunting in Wisconsin at the widest reading; from there, the rules tighten depending on whether you’re carrying a rifle, handgun, shotgun, muzzleloader, or air rifle. The controlling regulation is Wisconsin Administrative Code NR 10.09, which also bans certain ammunition types outright and applies a “reasonably capable” standard to whatever you bring into the woods.¹

Rifles: the .22 Caliber Floor and What Actually Works

The written minimum is .22 caliber. Soft-point, hollow-point, and bonded bullets all satisfy the expanding-projectile rule. Full metal jacket rounds are effectively prohibited because they’re built to hold their shape rather than open up.¹

Sitting on top of the caliber rule is a broader requirement: the weapon and ammunition must be reasonably capable of taking the animal. A firearm at least .22 caliber is treated as prima facie reasonable equipment, but that presumption doesn’t guarantee every .22-bore load qualifies in practice. There’s no written minimum energy or velocity in the code, so the “reasonably capable” language does the work.

A .223 Remington loaded with an expanding bullet meets the letter of the law. Larger cartridges like .243 Winchester, .308 Winchester, and .30-06 Springfield are the ones most hunters and wardens consider clearly appropriate for whitetail. If you’re choosing a rifle, the legal question is easy; the ethical question is where the “reasonably capable” standard lives.

What About Rimfire?

Wisconsin’s rifle rules don’t mention rimfire by name. What they require is a .22-caliber minimum, an expanding projectile, and equipment reasonably capable of harvesting a deer. Most rimfire cartridges — .22 LR and .17 HMR among them — don’t produce enough energy to clear that last bar on an animal the size of a whitetail. You could load expanding .22 LR hollow points and satisfy two of the three requirements, but a conservation warden would have a strong argument that the round isn’t reasonably capable of a clean kill. The handgun section of the code closes this door explicitly by demanding centerfire ammunition.

Handgun Requirements

Handguns are legal for deer, with stricter specs than rifles. A hunting handgun must be chambered in a centerfire cartridge of at least .22 caliber and have a barrel at least 5½ inches long, measured from the muzzle to the firing pin with the action closed. It must fire a single expanding projectile per shot.²

Muzzleloading handguns follow a separate track. A black-powder revolver or single-shot muzzleloading pistol must be at least .44 caliber, carry a barrel at least 7 inches long measured from muzzle to breech face, and fire a single projectile weighing at least 138 grains.² These must be cylinder- or muzzle-loading designs rather than cartridge guns.

Popular centerfire handgun choices include .357 Magnum, .44 Magnum, .454 Casull, and .500 S&W Magnum. A .22 Hornet meets the legal minimum but sacrifices energy in a short pistol barrel, which is why handgun hunters generally gravitate toward magnum cartridges.

Shotguns: Slugs Only, No Buckshot

Shotguns are legal for deer, but only with a single slug or ball. Buckshot is prohibited during any deer season, and you cannot even possess buckshot while hunting deer. The one narrow exception is a hunter carrying a valid, unfilled bobcat harvest permit during an open bobcat season that overlaps a deer season; that hunter may carry buckshot for the bobcat.³

The shot-size restriction runs wider than deer season alone. From June 1 through the last day of any gun deer season, you cannot possess shells loaded with shot larger than BB.³ Slugs used on deer still have to meet the expanding-projectile rule. Foster-style rifled slugs and sabot slugs both qualify. The code sets no gauge restriction, so a .410 is technically legal, though the reasonable-equipment standard makes it a hard sell for deer.

Muzzleloaders

Muzzleloaders can be used statewide during any firearm deer season. During the dedicated muzzleloader-only season, the rules narrow: the firearm must load its projectile from the muzzle. That excludes black-powder revolvers, which load through the cylinder.

The single expanding-projectile requirement applies here too. Round balls, hollow-point conicals, and expanding saboted pistol bullets all qualify. Muzzleloading rifles are generally recognized as needing at least .40 caliber, and muzzleloading handguns follow the .44 caliber floor with the barrel-length and projectile-weight requirements described above.² Most Wisconsin muzzleloader hunters run .50 caliber rifles, which have the broadest projectile and powder-charge selection for whitetail.

Air Rifles

Air rifles are allowed for deer in Wisconsin. The gun deer license covers airguns, and the same ammunition rules apply: single expanding projectile, .22 caliber minimum, and equipment reasonably capable of harvesting a deer.¹ The code sets no minimum muzzle energy or velocity for airguns, which pushes the burden back onto the hunter to choose equipment that can ethically take the animal.

In practice, only big-bore pre-charged pneumatic air rifles in .35 caliber and up generate enough energy for deer-sized game. If you’re going this route, .30 caliber or larger, projectiles of at least 150 grains, and at least 200 foot-pounds of muzzle energy is a reasonable baseline drawn from states that write explicit thresholds into their rules.

Prohibited Ammunition

Beyond the expanding-projectile rule that quietly rules out full metal jacket, Wisconsin bans several categories outright. You cannot hunt with tracer or incendiary ammunition. Bullets designed or modified to explode on impact, or to deliver poisons or drugs, are also prohibited.¹

You’ll see it claimed online that armor-piercing ammunition is banned for hunting under NR 10.09. The hunting regulations don’t actually address armor-piercing rounds. Wisconsin’s criminal code, at Wis. Stat. § 941.296, prohibits possessing armor-piercing bullets during the commission of a crime, but that’s a separate criminal-law provision rather than a hunting rule. The practical effect is still that most armor-piercing projectiles are non-expanding by design, which violates the deer-hunting expanding-projectile rule on its own terms.

Penalties for Getting It Wrong

Ammunition violations are among the easiest for a conservation warden to detect during a field check; the warden inspects the rounds in your firearm or on your person. Using the wrong ammunition, an undersized caliber, or a handgun that doesn’t meet the barrel-length rule generally falls under the state’s hunting-violation penalty provision, which carries a forfeiture up to $1,000. More serious violations, including poaching and repeat offenses, can rise to misdemeanor charges with fines up to $2,000 and jail time of six months or more depending on the specific statute.⁴

The consequence that catches many hunters off guard is license revocation. Wisconsin belongs to the Interstate Wildlife Violator Compact, so a Wisconsin suspension triggers automatic suspension in every other member state. Your home state treats the Wisconsin conviction as if it happened locally, and the suspension holds until Wisconsin confirms you’ve resolved the underlying violation. Losing hunting privileges across dozens of states because you loaded the wrong round is a price most hunters don’t consider until they’re paying it.

1
Wisconsin State Legislature. NR 10.09 Weapons and Ammunition
2
Wisconsin State Legislature. NR 10.09 Rule Text – Weapons and Ammunition
3
Wisconsin State Legislature. Order of the State of Wisconsin Natural Resources Board – NR 10.09
4
Wisconsin State Legislature. Wisconsin Statutes 29.971 – Penalties