Whatever the label used —combat, tactical, or personal defense— shotguns exist in various forms. They range from double-barreled to pump-action, semi-automatic and even lever-action.
Recently, a new genre of “shotgun” has arrived: the non-NFA “pistol grip firearm.”
Mossberg has been leading the way in this category with its pump-action 590 Shockwave, which appeared in 2017. This year, the company released the semi-automatic Mossberg 990 AfterShock, the focus of this article.
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The 990 Aftershock is manufactured from the start with a unique “Aftershock birdshead grip” and maintains an overall length greater than 26 inches. This is why it’s considered a “firearm” and not an NFA-regulated short-barrel shotgun (SBS), despite its 14.75-inch cylinder bore barrel. In other words, the Mossberg 990 has no stock and serves as a pistol-grip only shotgun.
Compact Firearm, Compact Action
It could be easy to assume that the Mossberg 990 AfterShock is just a cut-down Mossberg 940. But that isn’t actually feasible since the firearm possesses no stock. Since the Mossberg 940 action requires a stock extension to accommodate its recoil spring, Mossberg engineers had to blueprint a slightly different action to execute on the 990 AfterShock.
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The 990 AfterShock’s gas-operated action is housed within the machined aluminum receiver and forend under the handguard instead. The reliability of the 990 AfterShock is enhanced by its corrosion-resistant internal parts. Its gas piston, magazine tube, hammer and sear are all nickel-boron coated.
This 12-gauge firearm makes use of a 14.75-inch cylinder-bore barrel with a 3-inch chamber. With its signature AfterShock birdshead grip, this weapon has an overall length of 27.1 inches. To facilitate loading, the Mossberg 990AfterShock features an enlarged/beveled loading port, an elongated elevator and an anodized follower. The 990 AfterShock’s matte-black receiver and slim forend with M-LOK slots finish off aesthetics. There’s also that useful forend strap that keeps the support hand in place during shooting.
Legally Expanding My Stock Options
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My initial exposure to the 990 AfterShock happened at the Athlon 2025 Rendezvous. Mossberg’s staff brought some 990s to the event, and they were in action for two days just firing shell after shell. We got these firearms so hot to the point where Mossberg’s staff rotated different guns on and off the line to allow them to cool.
All of the rounds these firearms cycled during Rendezvous consisted of “low-brass” birdshot. Honestly I was impressed with the 990 AfterShock action functioning so well with this type of shotgun ammunition.
Semi-automatic shotguns have shown their capability afield for hunting. But few have shown the “hell and back” reliability necessary to gain the confidence for life-and-death scenarios.
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I was so impressed with Mossberg 990 AfterShock, that I actually decided to legally turn mine into a bona-fide short-barreled shotgun (SBS). This meant I had to go through the ATF’s NFA registration process and pay a $200 tax stamp.
Short Barreled, Long In Sight
Once I got the green-light to remove the birdshead grip and add a stock, I added a Mossberg 590 Speedfeed stock I had lying around. Adding a red-dot sight to my SBS’d Mossberg 990 AfterShock was also part of my original plan. Gone are the days of the underperforming brass bead!
Prior to legally converting my gun into an SBS, I had a Meprolight MPO Pro-F sitting on a Picatinny base over the 990’s receiver. This worked fine with the birdshead grip. But after SBS’ing this gun, I had lingering anxieties. I knew the optic could be mounted better. So I switched to Meprolight’s MPO Pro direct shotgun mount. Eureka! This is what I was seeking. The direct shotgun mount with the petite MPO Pro-F lowers the eye to right over the rib.
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I like the Meprolight MPO Pro-F because its enclosed-emitter housing isn’t affected by weather or environmental conditions. Rain, snow, and debris cannot interfere with the dot reticle, enabling accurate shooting in any conditions. This red-dot sight feeds on a CR1632 battery that gives up to 20,000 hours of runtime. I also found its multi-reticle system to work quite well with the Mossberg 990 AfterShock.
Self-Loading Superiority
The Mossberg 990 AfterShock’s semi-automatic gas action is key for uber reliability and flexibility of choosing ammunition. There can be no compromise or concern in terms of this. Its semi-automatic action not only made a difference in felt recoil, (especially based on prior experience with the pump-action Mossberg 590 Shockwave), but it also allowed me to stay on target more easily with multiple rounds fired more quickly and more naturally. It’s also nice not needing to rack the slide.
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Power Of 12-Gauge
I tested my Mossberg 990 AfterShock SBS with Hornady American Gunner Reduced Recoil and Critical Defense 00 buckshotloads. I also included Hornady Varmint Express #4 buckshot, Remington Ultimate Defense #4 buckshot, Remington LE 00, Federal Premium LE133 FliteControl and Federal #4 buckshot.
Federal’s Flitecontrol, Hornady American Gunner and Hornady Critical Defense are all loaded with specialized wads for tighter buckshot patterns. The result is tighter patterns and slightly longer effective ranges. For example, Flitecontrol prints 6-inch patterns at 20 yards! You’re lucky to hit a 6-inch pattern with a conventional buckshot load at 10 yards.
However, I think the role of the 990 AfterShock as a close-range blunderbuss could justify the use of conventional buckshot like the Remington products listed above. Users will have to determine what best suits their needs.
I also threw in some Winchester PDX 1 (currently labeled Defender in the Winchester catalog) 12-gauge loads into the mix for testing. The PDX 1 combines a 1-ounce slug and three 00 pellets. The Winchester PDX 1 is without a doubt, one of my favorite 12-gauge personal defense loads. Believe it or not, the PDX 1 load ironically harkens back to the “buck-n-ball” loads during the days of smoothbore muzzle-loaders. Winchester PDX 1 loads stretch preconceived 12-gauge lethality notions even further with its combination of slug and buckshot.
Range testing of the Winchester PDX 1 Defender raised eyebrows with its performance, combining the best of both worlds for the combat shotgun—single projectile performance and 12-inch buckshot pattern spread out to 20 yards, with one of the holes being made by the 1oz slug! If only one load is possible for use in a tactical shotgun, the Winchester PDX 1 may very well be it. The Meprolight MPO Pro-F is ideal for maximizing this potential.
Short Barreled Bludgeon
The Mossberg 990 AfterShock is a close-range hammer. Each double-aught pellet strikes with the force equivalent to .32ACP/.380ACP. The firing of six rounds of 00 buckshot from my 990 SBS translates into 48-54 (depending on 8 pellet or 9 pellet) projectiles sent downrange in a few seconds.
At 50 yards, I printed 3-inch groups with slugs. I also had no difficulty nailing steel man-sized targets at 75 yards. I’ll admit, there was also a certain amount of satisfaction derived from witnessing the 1-ounce slugs rocking the target back on its base.
I took the liberty to conduct some drills involving moving between barricades. (Think of emerging from a bedroom into a hallway or vice-versa). Another niche role the shotgun has found in the law enforcement arena is a CQB force multiplier, especially in/around vehicles. I used range cars on property to simulate responding to bad-breath distance ambushes. In all, I fired a couple hundred rounds through my Mossberg 990 AfterShock SBS. These shells consisted of buckshot, birdshot, and even slugs. I didn’t come across any reliability issues.
Last Shell In The Saddle
The Mossberg 990 AfterShock SBS’s simplicity, reliability and raw power exemplify why the 12-gauge continues to attract users. The nearly .75-caliber diameter bore is devastating. But by no means is the Mossberg 990 AfterShock SBS 12-gauge easy or beginner friendly. Whether it’s found in its default factory configuration or legally converted SBS, the 990 AfterShock best serves people with stout bodies and, more importantly, minds. There is no shame in choosing another weapon type if you are not capable of managing the recoil physically or the mental commitment to relying on such a short-range bludgeon.
As mentioned, my time with the 990 AfterShock in its original format convinced me of its viability. And more importantly its reliability. Beyond that, I noticed that having to shift operating components to the front of the receiver has the indirect benefit of a better-balancing shotgun.
I was already so impressed by the 990’s performance without a buttstock, so adding one and getting my tax stamp was a no-brainer.
And on that note:
While the non-NFA “pistol grip firearm” might be a recent phenomenon, stockless shotguns are actually old-school tactical tools. Their history traces back to niche roles within outfits like the US Marshals’ Witness Protection teams, police stakeout squads, surveillance units, high-value prisoner transport teams, etc. Each appreciated the close-range firepower potential of the compact shotgun, not to mention the intimidation factor.
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