Arkansas Fish & Game's take on barrel measurement:
Modern Gun
Modern guns may be used for deer EXCEPT:
- buckshot in a .410 shotgun.
- shot smaller than No. 4 buckshot in any shotgun.
- rimfire cartridges, military or full metal jacketed ammunition.
- centerfire rifles or handguns smaller than .22 caliber.
- handguns with barrels shorter than 4 inches. See illustration, right.
NOTE: The AGFC has approved for modern gun deer season the use of large-bore air rifles that meet certain standards. The large-bore air rifle must be at least .40-caliber, shoot a single, expandable slug, produce at least 400 feet/pounds of energy at the muzzle, and be charged from an external tank. Large-bore air rifles are not legal for harvesting bear or elk.
Muzzleloader
To be used for deer hunting, muzzleloading rifles must have a barrel 18 inches or longer and be .40 caliber or larger. Magnifying sights may be used. The use of shot is not legal. Legal muzzleloaders use flint, percussion cap, primer or electronic pulse, must have the bullet loaded through the muzzle and are not capable of firing a cartridge.
Hunters may use muzzleloading handguns with:
- barrels 9 inches or longer
- .45 caliber or larger if they shoot conical bullets (200 grains or heavier), or
- .530 caliber or larger if they shoot round balls.
A hunter may carry a muzzleloading handgun of any caliber as backup to a muzzleloading rifle.
Technically, a ROA isn't legal for taking deer in Arkansas.