Mossberg 990 Aftershock Review: A Fun, Gas-Operated Semi-Automatic

It only took seven years for us to get the sequel to the Mossberg Shockwave. I don’t know how many times I asked Mossberg about a semi-auto Shockwave-style firearm, but they’ve finally delivered. Mossberg was kind enough to send me one to review.

The 990 Aftershock: What’s The Deal

The 990 Aftershock is not a shotgun. It’s a firearm—an “other” if you will. The 990 Aftershock falls into this odd category due to its design. While it looks like a shotgun and functions like a shotgun, it’s not a shotgun. Shotguns are defined as having or as having had a stock. If a shotgun-like firearm is produced with no stock, it’s not a shotgun.

Since it’s not a shotgun, the barrel can be shorter than 18 inches. In this case, the barrel is 14.75 inches long. The kicker is that the gun has to be at least 26 inches long overall. If it falls below 26 inches, it becomes an AOW, which is another NFA category firearm. The Aftershock measures out to 27.125 inches.

The 990 Aftershock is a gas-operated semi-automatic design. It’s not an adaptation of the 940’s gas system. The 940 requires a buffer-style system in the stock. Mossberg designed a new gas system for the Aftershock that’s hidden entirely under the handguard. In a move best described as smart and consumer-friendly, the 990 Aftershock can accept 590 stocks and pistol grips.

This makes it a prime candidate to become a short-barreled shotgun. With tax stamps being reduced to $0 in January, the 990 Aftershock is primed to become a favored Form 1 gun. Since factory-produced short-barreled semi-auto shotguns are rare, the Aftershock seems like an easy option.

I reviewed the Aftershock as it came, as a semi-automatic firearm with a pistol grip only. My plan is to eventually get that Form 1 and add a stock, but that’s not necessary. It stands on its own as a firearm quite well.

Aftershock 990 Features

1 M-LOK Magazine Clamp

2 Optics Ready

3 Hi-Viz Front Sight

4 Ambidextrous Tang Safety

Running Ragged

Let’s talk ergonomics. These firearms tend to be rather interesting in their design. Mossberg ditched the standard Shockwave grip for their own take on the idea. It’s the same style of grip, but it feels thinner, with a rubber backstrap to help keep it nonslip and give you a little impact resistance. If you like the old grip, you can easily swap it out.

Up front, we have a solid handguard with the Shockwave-style strap. Just like before, the strap will dig into your support hand’s trigger finger. It gets irritating enough to rub your skin raw and create some serious and annoying pain. You can remove the bolts and reverse the strap, but do so at your own risk. Modifying any part of a gun is done at a risk to your own health.

What I love about Mossberg’s new semi-auto platforms is how big the controls are. The charging handle and bolt release are massive. They are easy to find and use. The gun has the standard tang safety, and it’s the new, upgraded Gen 2 type design that’s wider and easier to use than the already awesome Mossberg tang safety.

The loading port is beveled for easy loading on the fly. It’s a nice touch and one that my fingers appreciate. My only complaint is that I wish the handguard had more aggressive texturing, and it might be a perfect candidate for Talon-style grips.

Going Fast

Any 12-gauge weapon without a stock can be hard to handle. Recoil is very much a thing, and owners of Shockwaves quickly learned to either mitigate recoil or how to treat bloody noses. The Aftershock still packs a punch’s worth of recoil, but the semi-auto action makes it tamer than a pump-action design.

With practice, I was able to land two rounds of fully powered buckshot on target in less than one second. It took a fair bit of practice and isn’t as fast as a stocked shotgun, but it’s achievable. The recoil isn’t brutal, but it’s not for shooters who haven’t mastered the art of push/pull. The Aftershock requires good recoil mitigation to avoid getting punched in the face.

Reduced recoil ammo is the way to go. With Federal FliteControl, I can easily avoid kissing the pistol grip. Fiocchi Defense Dynamics’ reduced recoil is a cheaper, more common option that works well for training.

The Aftershock has a high-visibility front sight that’s easy to see and fast to get on target. If the sight isn’t enough, the optics-ready receiver will be. You can slap a red dot on this sucker and feel some real speed. There are tons of dedicated 590 optic mounts, and it’s a great way to get fast with this gun.

Patterns are about what you expect. Bare bones ammo can hold a five-inch pattern at seven yards and a seven-inch pattern at ten yards. FliteControl works like an absolute champ. At ten yards, it’s not bigger than a fifty-cent piece and looks like a slug.

Keeping It Fed

I fired 500 rounds without any malfunctions. It chewed through buckshot, birdshot, slugs, and reduced recoil ammo with no problems. No, it doesn’t run mini shells because it’s a semi-auto, and that’s a silly expectation.

Overall, I found myself loving the 990 Aftershock. With free tax stamps around the corner, I will probably make it an SBS, but even if I don’t, the gun works quite well without a stock. It’s an absolute blast to mag dump this thing from the hip, and the smiles are often worth it.

990 Aftershock Pros and Cons

Aftershock 990 Starter Pack

So what’s next? Well, if you decide to get the Aftershock 990, you’re going to need to pick up some must-have basics. Here’s our recommendation for what you need to get started.

• Gun Cleaning Kit: Otis All Caliber Elite Range Box on Amazon or build your own personalized cleaning kit with premium components.
• Shooting Glasses: All it takes is one piece of rogue hot brass, and you’ll learn the importance of shooting glasses. But not all glasses are built the same. See our recommendations for the Best Shooting Glasses.
• Hearing Protection: Firing a gun without wearing proper ear protection can be very dangerous and detrimental to your hearing. Find out the best hearing protection for you in our full-length review.
• Storage: Check out our article on the Best Biometric Gun Safes
• Targets – If you’re wanting a great resource for shooting practice or zeroing your optics on your optics rifle or pistol, download our FREE Sighting in Targets below.

Mossbery Aftershock 990 Accessories 

The best optic for the job is the Vortex Viper Shotgun Red Dot. See below to get the best deal for that.

1. Vortex Shotgun Red Dot

Enclosed Emitter Attaches Directly to 990 Multiple Reticle

See Best Price

How To Care For Your 990 Aftershock

Not only do you need to keep your firearms safe and secure, but you’re also going to need to know how to take care of them. While scouring the internet, we came across this excellent video:

Important Links And Manuals For Your Aftershock 990

For more info regarding the Aftershock 990, check out the following resources:

• User Manual for Aftershock