In 2017, Mossberg announced the release of its unique 590 Shockwave, a shortened, shotshell-firing “firearm,” per ATF, that did not require regulation under the National Firearms Act. The Shockwave was shorter than traditional shotguns and did not use a shoulder stock, but it still maintained the 590’s pump-action mechanism. In 2025, Mossberg added to the category with its 990 Aftershock, which uses a semi-automatic operating mechanism while still maintaining a compact form factor. Watch our “American Rifleman Television: Rifleman Review” segment above to see the details.
“Again, it’s a firearm by ATF definition,” American Rifleman’s Brian Sheetz said. “It’s greater than 26 inches in length, it has a bird’s head style grip, not a shoulder stock, and it has a 14.75-inch barrel. The tubular magazine in this gun, you know, obviously being here within the confines of the fore-end, holds five 3-inch shells. So on the fore-end on the Aftershock, you’ve got the same type of nylon webbing loop that you find on the Shockwaves.”
The Aftershock Grip incorporated into the design features a rubberized palm pad that absorbs recoil energy from firing, and the design incorporates a number of ergonomic updates, including a knurled charging handle, ergonomic bolt-release button and a new safety design.
“One thing that Mossberg has done recently and really debuted on this gun was this enlarged, tang sliding safety,” Sheetz said. “So when the gun is held with the hand in this manner, that’s really convenient to be able to manipulate with the thumb, forward for fire, rearward for safe.”
Other features include a rear sling-swivel stud located at the rear of the bird’s head grip, along with M-Lok attachment slots on either side just ahead of the polymer fore-end. There’s also a bright-orange, anodized-aluminum magazine follower that gives users a clear indication that the magazine is empty.
“Another feature that a lot of people don’t realize is incorporated on some of these guns that, some of the Mossbergs, particularly the 990, there is an indicator here that protrudes into the trigger guard,” Sheetz said. “It’s a silver pin that protrudes slightly into the trigger guard. So what that is is a cocking status indicator. If that’s protruding into the trigger guard, the gun is cocked.”
Mossberg has also made several SPX models available in its 990 Shockwave line, which includes a modified fore-end that incorporates a heat shield, along with a receiver cut to accept red-dot optics.
“The Aftershockâs format constitutes a somewhat unique situation, and there are some folks that are even securing the paperwork and adding shoulder stocks to this model,” Sheetz said. “And that is something that has to be done through the National Firearms Act in order to convert them to short-barreled shotguns. But as it stands, the Aftershock is defined as a firearm. It’s not a handgun, technically. It’s not a rifle, and it’s not a shotgun. It is a shotshell-chambered firearm.”
To watch complete segments of past episodes of American Rifleman TV, go to americanrifleman.org/videos/artv. For all-new episodes of ARTV, tune in Wednesday nights to Outdoor Channel 8:30 p.m. and 11:30 p.m. EST.
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