The extent to which United States gun laws apply to muzzle loaders is a frequent topic of discussion. Most shooters have heard that gun laws generally apply only to "firearms" and that most muzzle loaders not considered firearms. Consequently, there is a common belief that all muzzle loaders are exempt from firearms regulation.
It is generally true that many restrictions imposed by the Federal Gun Control Act of 1964, or GCA, do not apply to muzzle loaders. For example, Federal law does not require that muzzle loaders be sold through a licensed dealer. As a result, muzzle loaders can be mail ordered across state lines. Similar, convicted felons, those with substance abuse problems, and pretty much anybody else are legally permitted to purchase a muzzle loader under federal law.
However, just looking at this question at a very high level can lead to a number of issues and potential violations of the law. For example, not all "muzzle loaders" are exempt from the restrictions of the Gun Control Act. In addition, many States have laws which restrict certain people ability to legally own muzzle loading guns.
Federal Gun Laws
There are two primary federal gun control laws in the United Sates: (1) the Federal Gun Control Act of 1968 (GCA); and, (2) the National Firearms Act of 1934 (NFA). The Federal Gun Control Act or GCA broadly regulates the firearms industry and firearms owners. Generally, the GCA prohibits the interstate firearms transfers except among licensed persons. The National Fire Arms Act or NFA, on the other hand, regulates what are considered "gangster weapons." Example of guns which are regulated by the NFA machine guns and short barreled shotguns.
The Federal Gun Control Act or 1964 or GCA
The GCA has the widest application to most firearms. To the extent that you have a gun which is classified as a "firearm" under the GCA, there are a number of restrictions which apply to the ownership, possession or sale of the weapon. Consequently, the threshold question when considering the application of the Gun Control Act is to determine whether your gun is a "firearm." The GCA starts with a very broad definition which includes any weapon (including a starter gun), which will, or is designed to or may readily be converted to expel a projectile by the action of an explosive. However, the definition of the term “firearm” goes on to exclude any weapon which is an “antique firearm.” See: 18 U.S.C. § 921(a)(3). Fortunately, the term "antique firearm" includes most muzzle loading guns, regardless of the date of manufacture. As a result, must muzzle loaders are considered "antique firearms" under the GCA and not subject to regulation as "firearms".
Under the GCA, there are three groups of guns which will qualify as an antique firearms and excluded from regulation as firearms.. See: 18 U.S.C. § 921(a)(16). The first two groups of “antique firearms” are pretty straight forward. First, guns manufactured in or before 1898 are antique firearms. Second, a replica of of a pre-1898 firearm is not designed or redesigned for using rimfire or conventional centerfire fixed ammunition are also considered antique firearms.
The third category of antique firearms is where some grey areas begin to arise. The statute states that any muzzle loading rifle, muzzle loading shotgun, or muzzle loading pistol, which is designed to use black powder, or a black powder substitute, and which cannot use fixed ammunition are considered antique firearms; so long as the gun does not incorporate a frame or receiver which was converted into a muzzle loading weapon or which can be readily converted to fire fixed ammunition. Under these definitions, there a number of commercial muzzle loaders which are a number of considered firearms and subjection to the restrictions of the Gun Control Act. Examples of muzzle loaders which are considered firearms include: Savage Model 10ML; Mossberg 500 shotgun with muzzle loading barrel; Remington 870 shotgun with muzzle loading barrel; H&R/New England Firearm Huntsman and the Thompson Center Encore and Contender. In addition, muzzle loaders which were built on the receiver of a modern gun are considered firearms. While it is unlikely that these guns could ever be reconverted to shoot modern ammunition, they are still considered firearms under the Gun Control Act.
The bottom lines is that for the vast majority of muzzle loaders, the GCA does not require that the guns be sold through a licensed dealer and the muzzle loaders can be purchased across state lines. Similar, convicted felons, those how use controlled substances (including users of medical marijuana) , and pretty much anybody else are legally permitted to purchase a muzzle loader under federal law. However, this rule is not absolute and you do need to pay attention to whether certain of the more modern muzzle-loaders will qualify as "antique firearms."
Muzzle loaders and the National Fire Arms Act.
he National Fire Arms Act was passed shortly after the repeal of Prohibition and was intended to regulate what were considered "gangster weapons" such as machine guns and short barreled shotguns.
Muzzle loaders are not generally thought of as gangster weapons. But what about my blunderbuss, which is the mother of all sawed off shotguns? Other than the fact that the gun is a muzzle loader, my blunderbuss would qualify as a short barreled shotgun and would be highly regulated by the National Fire Act. Fortunately, an exemption is found in the National Fire Arms Act for most muzzle loaders.
Like the Gun Control Act, the National Firearms Act provides an exemption for Antique Firearms. However the two gun control laws contain a different definitions of what constitutes an Antique Firearm. For the purposes of the National Firearms Act, the term includes any gun which utilizes a matchlock, flintlock, percussion cap or similar type of ignition system. Since my blunderbuss is a flintlock, it is not considered a short barreled shotgun. This interpretation of the law is confirmed by the ATF Handbook which indicates that even though this weapon [a short barreled shotgun] may exhibit a barrel shorter than 18 inches and/or an overall length less than 26 inches, it is not subject to NFA regulations governing those dimensions because it employs a primitive ignition system identified as an exempting characteristic.
In addition to regulating short barreled guns, the National Firearms Act also regulates "destructive devices" which are basically very large bore weapons. A destructive device is defined by the NFA as a weapon which " have a bore of more than one-half inch in diameter (.50 inches or 12.7mm), except a shotgun or shotgun shell which the Secretary finds is generally recognized as particularly suitable for sporting purposes." There are a number of muzzle loading weapons which could be included in this definition. For example, muzzle loading cannon, punt guns and large bore guns are frequently seen at muzzle loading events. Under the NFA, these muzzle loading weapons are not considered "descructive devices". The frequently asked questions section of the ATF website confirms this result and states the muzzleloading cannons not capable of firing fixed ammunition and manufactured in or before 1898 and replicas thereof are antiques and not subject to the provisions of either the GCA or the NFA.
What Does State Law say about Muzzle Loaders.
Just because federal law does not define a muzzle loader as a firearm does not mean the anyone can purchase or possess a muzzle loader. The states are free to adopt more restrictive laws. For example, in my home state of Colorado, felons (regardless of when the crime was committed) are precluded from possessing any firearm. Under Colorado law, the term firearm is broadly defined as "any handgun, automatic, revolver, pistol, rifle, shotgun, or other instrument or device capable or intended to be capable of discharging bullets, cartridges, or other explosive charges." There is no exclusion for muzzle loaders and they are treated as ordinary firearms for possession and carrying purposes in Colorado. As a result, in Colorado felons are not permitted to purchase or possess a muzzle-loader. This includes the use of muzzle loaders for hunting purposes.
The bottom line is that just because your muzzle loading gun is legal in your home state, there may be restrictions in other states. The NRA maintains an excellent synopsis of state gun laws, including those laws which pertain to muzzle loaders, at http://www.nraila.org/gun-laws/state-laws.aspx