Mossberg 990 Aftershock: Tiny, Savage, Semi Auto

Mossberg finally drops a semi auto Shockwave style thumper, and the 990 Aftershock brings real gas gun control to a compact 12 gauge that hits hard up close.

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Mossberg upended the shooting industry in 2017 by introducing the 590 Shockwave. The Shockwave is not a shotgun by definition, because it features a 14-inch barrel and is just over 26 inches in overall length, which means it isn’t a short-barrel shotgun and as such does not come under the National Firearms Act. To me this a situation where if it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck. It’s a shotgun.

Since that introduction many different brands have introduced pump-action Shockwave-style firearms. A few brands even took the Shockwave concept and applied it to semi-automatic shotguns. I used a Remington TAC-13 a few years back which features Remington’s excellent V3 gas system to create a semi-auto firearm. I always wondered why Mossberg didn’t come out with a semi-auto version. No need to guess any more since the Mossberg 990 Aftershock is here.

🛒 Check Current Price for Mossberg 990 Aftershock on GunsAmerica

The Mossberg 990 Aftershock is an all new gas operated, semi-automatic shotgun chambered in 12-gauge with a 3-inch chamber. There are multiple versions available. One is an 18.5-inch barrel model, a 14.75-inch barrel model which I tested, and a version equipped with a Crimson Trace Lasersaddle. In hand, the 990 Aftershock with the 14.75-inch barrel is only 27.1 inches long and weighs about 6 pounds unloaded. It feels like a small heavy stick. A small stick with a big whack. In fact, 5+1 rounds of whack.

What I like about the 990 Aftershock is that Mossberg incorporated features found on their Model 940 semi-auto shotguns and applied them to the 990 Aftershock.

Like the enlarged and beveled loading port and elongated elevator which eases loading the 990 with no pinched thumb. Controls, knurled charging handle, paddle-style bolt release, and ambidextrous safety, are all oversized making the 990 easy and fast to operate with or without gloves. The forend wears a strap which is a necessity with these types of firearms. Recoil can be a bear and the strap ensures your support hand stays in place on the forend and doesn’t slip past the muzzle.

I’ve used Shockwave style firearms without the strap and it can feel like you are trying to hang onto a fat slippery, wiggling eel in recoil. Just like with an SBR or large format pistols such as AR15 or AK pistols, it is important to keep hands clear of the muzzle. The forend is relatively thin for a gas system gun. The piston is inside the forend and on many sporting guns, the piston can make the forend feel thick in hand.

What I also liked about the 990 was that Mossberg didn’t forget that this is a defense weapon. The M-LOK accessory slots on the sides and bottom allow you to attach a tactical light that is in close proximity of your support hand thumb when you need to turn it on.

The grip was also thought out with a rubberized palm that offers some cushion from recoil. There is also a QD cup in the grip butt perfect for use with a one-point sling.

The Aftershock is a close quarters style weapon. Ideal for cramped environments like the hallway of your home, it is also the type of companion you may want with you in your vehicle if things go sideways on the road.

These are difficult firearms to shoot, however, since it is too heavy to fire like a pistol and there is not a stock or brace to steady the weapon while you aim. As such you can’t get a steady aim with these types of firearms and that’s the reason why they are close range weapons. I find two ways of shooting these firearms works out best for me.

One way is to hold the Aftershock in front of your body and use the red fiber optic tube to aim with. Make sure the 990 is away from your face or you will soon realize why it should be. This technique offers the best accuracy, and as I found depending on the load the Aftershock can be surgical. A 3-inch group with Hornady Critical Defense at 15 yards is impressive.

The second way is to shoot the Aftershock is from the hip with the Aftershock on the side of your body. This technique offers less accuracy but is effective at close range. With the Aftershock at your side, your arms absorb the recoil.

I ran two different 00 Buck loads and a bird shot load through the 990. For the tactical loads I used Hornady Critical Defense 00 Buck and Panzer Defense 00 Buck. As side note: I’ve found that Hornady Critical Defense load consistently shoots tight patterns compared to other brands of 00 Buck ammo. It averaged a 3-inch pattern at 15 yards while the Panzer averaged over 4 inches. The Federal Ultra Clay & Field loaded with 1-1/8 ounce of #8 birdshot spewed a 21 inch pattern on average. Bird shot might be a good option to avoid over penetration especially in the confines of your home. The bird shot does not have the energy of buck shock, and will penetrate less. It will also over spray the target which is something to consider when deciding on a defense load for your situation.

Loading up the Aftershock I found the beveled loading port made inserting shells fast and easy. I didn’t pinch my thumb on the last round loaded. The over sized controls allow me to operate the 990 smoothly. I hate bolt release buttons that are small and hard to press. Loading up with Federal bird shot and ripping through a magazine of shells shredded the cardboard target. Shooting from the hip the Aftershock was fairly easy to control when shooting fast. Recoil is stout; your arms and hands take all the abuse. The strap on the forend keeps your hand in place. Not only does it allow you to hold on and keep away from the muzzle, it keeps your hand off the hot barrel.

Point shooting with the 00 Buck loads I used the push pull technique, pull the grip with my firing hand while pushing with my support hand, to steady the Aftershock. At 15 yards it was an easy task to get all 00 Buck pellets on target. Shooting the Aftershock this way helps to manage recoil. Remember to keep it away from your face or else you might get whacked. The speed and amount of 00 Buck pellets you can get down range is impressive. The Aftershock cycled smoothly and even with the light Federal birdshot load. It cycled relentlessly with no issues. I ran about 200 shells through the Aftershock and full disclosure I had a grin on my face. It is a fun firearm to shoot.

The 990 Aftershock reverberates with power. I admit that it is a fun firearm to shoot, but it is more difficult to shoot than a handgun, shotgun or rifle. It is an expensive option for home defense, compared to similar pump-action firearms. Firearms like the Aftershock are unique and take a training just to be competent and consistent, but it does offer a lot of fire power in a small package.

• Pros: Compact 12 gauge package, gas system softens the chaos, oversized controls and beveled port run fast, M-LOK timing with light is intuitive, strap keeps you safe and planted.
• Cons: Still tricky to aim compared to a stocked shotgun, recoil is stout without a brace, costlier than pump options, technique dependent for best results.