Mossberg Shockwave 590S

World’s most omnivorous shotgun?
; .

First, let’s get something clear — this is a magazine for discerning shooters who are experienced and don’t fall easily for the latest “Gun of the Month” or “Technique of the Week” hype. We strive to present articles packed with real-world information written by a team of world-class writers.

Having made this point, I must interject something — The Mossberg 590S Shockwave is purely, absolutely cool, possibly straying into the realm of “Kick Butt!”

Yeah, the Shockwave 590S is great big fun to shoot but getting back to my chronological age, I’ll point out it’s a great special-purpose self-defense scattergun with a major improvement giving it even greater utility.

This enhancement is the added capability to feed shorty shotshells, a modification many Shockwave users previously made by adding aftermarket parts. Now, straight out of the box, you can throw over a half-pound of lead downrange faster than President Biden can churn out anti-gun executive orders.


The Mossberg 590S Shockwave — A short-but-sweet 12-gauge pump gun for
those intimate moments when bad breath isn’t your biggest concern …

The Legal Mumbo-Jumbo

Before getting to the fun stuff, we need to examine the one big issue many folks have trouble understanding: How is this thing not considered an illegal sawed-off shotgun? I’ll admit it has more than a passing resemblance.

More-restrictive state or local laws aside, the BATF has officially decided — at least for now — the Shockwave is a “firearm,” nothing more or less. Note we didn’t say “shotgun,” “NFA weapon,” “pistol-grip shotgun” or any other legal “thing.” Therefore, the Shockwave is not subject to the strictures of those categories. Federally at least, if you’re eligible to own a modern firearm under the 1968 Gun Control Act, you can own a Shockwave.

This is possible because of design work, especially the “bird head” grip, specifically intended to work within the existing legal framework. It’s not concealable (legally speaking) due to length and it’s not designed to be shoulder-fired, so it’s technically not a shotgun. In other words, the government couldn’t find an existing legal definition to cover it, so it’s just considered a generic “firearm.”

Keep in mind there are a couple of things you could do with a Shockwave or any such shorty scattergun to get yourself in plenty of trouble under federal law — you can’t carry it concealed and you can’t put any other type of grip or stock on it. You also can’t fire it from the shoulder, though it would be almost physically impossible and incredibly painful if you tried. Regardless, doing any of those things terminates the legal design features and invites trouble with the Feds.

As of this writing, the administration is making noise about trying to re-classify these as something subject to more regulation and tax such as “NFA weapon,” so stay tuned. My advice — get ’em while you can.


The Heart Of The Matter

We’ve messed around with the 590 Shockwave before and find it highly useful for certain specific situations and missions. This is not an all-purpose, general defense shotgun, oops, sorry, I meant “firearm,” but in certain circumstances it is your best choice. Unlike some other pint-sized shotguns, it’s also pure unadulterated fun to shoot now that shorty shotshells are on the menu.

The original Shockwave, and all 500-series Mossberg shotguns on which it’s based, could not handle “mini” shotgun shells exemplified by the Federal Shorty shotshell line. These are 12-gauge shells downsized to only 1-3/4″ in length rather than the standard 2-3/4 or 3″ of “normal” shells. Most pump shotguns won’t accept them as a matter of course unless you install certain aftermarket parts or otherwise modify the gun. Mossberg saw this and smartly incorporated the popular modification so your new 590S will gobble up nearly any 3″ and under 12-gauge shell you can stick into its maw.


To test the omnivore premise, Brent loaded a literal smorgasbord of shells,
long and short, buck and slug, even a plastic “less lethal” round, then tried to
emulate full-auto … with predictable results. The target was destined for the trash
can and the Mossberg 590S digested the mixed-up shells without pause.

To test the omnivore premise, Brent loaded a literal smorgasbord of shells, long and short,
buck and slug, even a plastic “less lethal” round, then tried to emulate full-auto … with
predictable results. The target was destined for the trash can and the Mossberg 590S
digested the mixed-up shells without pause.

Aimed fire using the front sight by holding the gun up to eye-level is actually
quite easy at close range — and quite devastating to the recipient.

Shell Shock

There are several advantages to the mini shells. First is capacity — without modifying the gun, you’ll get several more shells into the magazine. In the case of the Shockwave 590S, I jammed three extras into the tube for a total eight versus five with 2-3/4″. When you’re talking slugs, you’ve just added three additional ounces of hot lead to your blaster.

Of course, there is a trade-off: payload. The slugs are “only” one ounce, while #4 buck and #8 shot loads weigh in at 15/16 oz. Less lead equals less kinetic energy so there is an official reduction of “power” on the receiving end. But, considering this gun is largely combat-ineffective the past 20–25 yards, who really cares?

Fortunately, for the minor sacrifice of terminal energy there is a huge upside — reduced recoil and enhanced controllability.

The 590S can be a handful to shoot, especially if you’re gungy enough to try full-house 3″ slugs. With the shorty shotshells, you get more of ’em and they kick significantly less so in my mind, the benefit outweighs any negatives. Fortunately with the 590S, you can also mix mini, 2-3/4 and 3″ shells at random so you have plenty of options.


One other change Brent made was the Streamlight TL-Racker. It includes a
1,000-lumen LED light and nylon handguard. Forego using the handguard at your own risk!

The operation of the 590S, aside from the Billy Goat-like ability to digest any
length shell, is basic and easy for anyone who has ever run a pump gun.

Test Gun

Though the gun is perfectly serviceable straight out of the box, I decided to add a couple of personal-choice touches. First, I replaced the factory fore-end with Streamlight TL Racker, a fore-end that includes a 1,000-lumen LED light powered by two CR123A batteries. I felt this is important because a fighting gun, even one without much room to mount a light, is naked without some type of onboard illumination device. The TL Racker installed easily and includes a nylon hand strap like the factory original, which I highly recommend you use to avoid earning nicknames like “Stumpy” or “Two-Finger Magee.”

The second modification was an NDZ extended safety. The safety on the Mossberg 500 series of shotguns is light-years better, ergonomically speaking, than the one on my beloved Remington 870. However I like the NDZ version because it is slightly taller and extra-deeply contoured for a more positive thumb engagement. I ordered the red anodized aluminum version because it’s easier to see against the black receiver.

Otherwise the gun is a straightforward 500/590 platform with the aforementioned internal modifications to feed shorty shells.

The stock is known as a “bird’s head” style. It looks ungainly but is actually quite comfortable to carry and shoot. I think it was probably modeled after somebody’s old-school illegal sawed-off shotgun but it works amazingly well and does pass legal muster. It also includes a single sling swivel on the end, though you must refrain from hiding the gun under a coat or other concealment as this would take things into “NFA weapon” territory.

The barrel is 14.4″ and crowned with a simple golden bead front sight. There is no rear sight though our test gun receiver was drilled and tapped for a rail. It’s actually fairly easy to aim by holding up and using the front sight if you choose. Given the intended use of this particular gun, I would recommend you refrain adding any gear-snagging gadgets such as lasers or red dots.



Now I’ll endeavor to answer the big question: Why does such a gun exist and why does anyone need one?

As mentioned earlier, this certainly isn’t a general-purpose home-defense shotgun. Given the rig, even a 25-yard shot is pretty challenging but if you keep this “limitation” in mind, what you have is a relatively small, easily-controlled gun capable of throwing 9 oz. of lead (8+1) at a problem as fast as you can cycle the action. In my testing using shorty shells, I could empty the gun inside of four seconds even when I wasn’t trying hard to channel my inner Rob Leatham. After a few blinks of the eye, the cardboard silhouette target 15 feet away — average residential bedroom size — had been shredded into hamster bedding.

Imagine having the same capability tucked in an umbrella stand at your front door, lying next to your bed or nestled behind your vehicle’s front seat.

Therein lies the beauty of the Shockwave 590S — if you need to repel boarders at close range, a situation where you’ll probably need plenty of lead in a hurry, the Shockwave 590S might be the most devastating thing this side of an antipersonnel mine.

And, last I heard, the government isn’t much interested in allowing you to own one of those.


The Bird’s Head grip on the 590S is short but officially legal. It might look
odd but is quite comfortable to hold and actually keeps felt recoil within decent limits.

The Verdict

On top of the benefits already discussed, the Shockwave 590S is also relatively affordable for a heavy-duty defensive firearm. As of this writing the price wasn’t set in stone but a standard Shockwave 590 starts with an MSRP of $500 so we’d anticipate the 590S will be in the same ballpark. The gun will be available in four versions — a state-compliant “Mockwave” with a 20″ barrel, along with full-sized-stock 18″ or 20″-barrel models featuring 13+1 capacity, M-Loc forend and interchangeable chokes.

In total — the 590S is a short, federally legal, easily handled, higher-capacity, more controllable shotgun perfect for close-range defense. You give up a bit of muzzle energy but you won’t really miss it inside of 20 yards. Mossberg has created a winner, which is the reason why I not only tested the 590S Shockwave for this article but became a buyer too!

Of course, all these reasons aside, it’s still awfully darn fun to shoot — but I’d never buy a gun just for fun.
As far as my wife knows.

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