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Mossberg Is Making A Wave: Legality And Classification Of The 590 Shockwave

We have received numerous questions regarding the Mossberg 590 Shockwave. This firearm shoots shotgun ammunition, but has a new type of pistol grip and a barrel length of only 14 inches. It is marketed as a non-NFA weapon, which does not require a tax stamp. The question: IS IT LEGAL?

The Shockwave is the newest addition to the Mossberg family. Built around their popular 590 platform, it features a 14” barrel and an innovative hand grip that allows the user to hold the gun much like a traditional shotgun. It is just over 26 inches in total length. Pistol-grip shotguns have long been chastised for their dangerous recoil and inaccuracy. Without a shoulder stock to absorb recoil and stabilize aim, the pistol-grips have not been a popular option. But the Shockwave’s grip is shaped much like a traditional grip, where your hand sits on top of the grip rather than behind it. The angle of the grip has shooters swooning over the ease of use and the short barrel makes this item ideal for truck guns or home defense.

With a 14-inch barrel and an overall length of just over 26 inches, many are wondering if this is a short-barrel shotgun as defined by the NFA? To answer the question of this weapon’s legality we must look at the federal definition of a short-barrel shotgun.


Federal law defines a shotgun as a weapon designed and intended to be fired from the shoulder and designed to use the energy of the explosive in a fixed shotgun shell to fire projectiles. 26 U.S. Code § 5845(d). A shotgun must have an overall length of at least 26 inches and a barrel length of at least 18 inches. The Shockwave has a 14-inch barrel, four inches short of the federal requirement. But Mossberg was careful when designing this firearm. The hand grip is permanently affixed to the action and the barrel and does not have a shoulder stock. That means it is not designed to be fired from the shoulder. While it is certainly possible to fire this gun from the shoulder, it would likely result in injury to the user. It is clearly not designed or intended to be fired from the shoulder. So, it can’t be a shotgun under the federal definition. If it’s not a shotgun, what is it?


In a letter to Mossberg, the ATF states that under the NFA this gun does not require registration with the ATF. But they don’t explain what “this type of firearm” actually is. The ATF merely states this is a firearm as defined by the Gun Control Act. Some speculate, that because the ATF does not require registration, this item must be a pistol. Under the federal definition a pistol is “a weapon originally designed, made, and intended to fire a projectile (bullet) from one or more barrels when held in one hand, and having (a) a chamber(s) as an integral part(s) of, or permanently aligned with, the bore(s); and (b) a short stock designed to be gripped by one hand and at an angle to and extending below the line of the bore(s).” 27 CFR § 479.11. That wordy definition basically has two important aspects: designed to be fired with one hand and a short stock designed to be gripped in one hand.

Very few people could imagine safely shooting a 12-gauge shotgun with one hand. But the Shockwave is not a “shotgun.” The grip is designed to be held in one hand, and while most people would use a second hand to stabilize the firearm, the Shockwave can be fired with just the one hand. In fact, I have done so myself. I don’t recommend trying this at home, but it can be done. The grip is definitely designed to be gripped in one hand. So, it seems that this firearm could be classified as a pistol—a pistol that happens to shoot shotgun ammunition.


When the Shockwave was first introduced, it appeared to be an illegal firearm under Texas state law. Texas law defines “shotgun” without the requirement of being designed to be fired from the shoulder. Ironically, Mossberg manufactures the Shockwave in Texas. Needless to say, citizens of this gun-friendly state were not happy with this result. How could it be legal under federal law, but illegal under Texas law? Because Texas’s definition of a shotgun is broader, the Shockwave likely was considered a short -barrel firearm under state law. Texas Penal Code section 46.05 criminalizes possession of an unregistered short-barrel firearm. This result was non-sensical, because Texas law required registration of the Shockwave with the ATF, but the ATF stated it did not require federal registration. The legislature corrected this strange result with H.B. 1819. It clarified the section of the penal code dealing with NFA items by adding language that exempts items that are not subject to registration with the ATF. Therefore, under the new Texas rules, the Mossberg Shockwave is exempt from section 46.05 and is now legal in Texas.

So there you have it. The Mossberg Shockwave is a legal firearm in Texas. We should note that modification of the Shockwave is not a good idea. If you buy the Shockwave, make sure you do not saw off the back end and replace it with a shoulder stock. Such a modification would render your Shockwave an NFA item. Without a tax stamp and proper paperwork, possession of that modified Shockwave would be illegal. Also, be aware: if you are in the market for a 26-inch, 12-gauge pistol and you are not in Texas, check your state’s laws before picking one up. Each state is different and even in Texas the Shockwave was not legal until the law was changed. Just because you find it for sale does not make it legal. Take the time to know the law!

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