We recently tested three shorty-type shotshell-chambered firearms, one of which was a new Mossberg model, with a diverse group of mini shotgun shells to see if any of the three could handle the 1¾-inch shotshells reliably. In particular, the Mossberg 590S Shockwave firearm is purportedly designed for factory reliability with mini shells. If the gun were to work as advertised, the 590S would go a long way toward legitimizing the mini shell and its niche popularity.

However, after shooting two Mossberg 590 pump firearms and a Remington TAC-14 pumpgun, we have to point out our disinclination toward these units when compared to a standard shotgun, such as a Black Aces Tactical Pro Series S Max, tested separately. Aside from their reliability issues with the mini shells we focused on this issue, the Shockwave-type guns are also very difficult to use well, which we detail in more depth below.

Also, we remind you that these Shockwave-type firearms aren’t shotguns by definition, because they have 14-inch barrels and are just over 26 inches in overall length, which means they aren’t short-barrel shotguns and regulated as such under the National Firearms Act. The Shockwaves and TAC-14s aren’t legal everywhere, including a couple of usually gun-friendly jurisdictions. Never add a shoulder stock or pistol grip stock to the Shockwave types because this is illegal. Such modifications convert a Shockwave from a shotshell-chambered firearm to a short-barrel shotgun. Just be careful.

Mini Shell Testing

We previously tested mini shells in the August 2020 issue. Interest in these shells and the introduction of the 590S spurred this follow-up test. Unfortunately, we were unable to obtain the excellent Nobel Sport Italia (NSI) MiniBuck 6P, a 12-gauge 2.25-inch 7⁄8-ounce shotshell with six 00 buckshot pellets rated for 1250 fps. As far as we can learn, they are out of production. This is a shame because these were the best in previous testing. Instead, this round we were able to test mini shells from Aguila, Federal, Firequest, and Mason Munitions. We fired the rounds in the 14-inch-barrel Shockwaves and the TAC-14, as well as 18.5-inch barrels in the Black Aces Tactical Pro Series S Max semi-auto, a Remington 870 full-size pumpgun, and a full-size Mossberg Maverick pump.

The well-known Aguila Minishell, a 12-gauge 1¾-inch shotshell with a 5⁄8-ounce payload of 11 buckshot pellets (seven No. 4s and four No. 1s) is rated for 1200 fps, and it fired reasonably tight patterns from 18.5-inch-barrel shotguns but blossomed to 13-by-9-inch spreads out of the Shockwaves. The load delivered around 600 foot-pounds of energy on average with its dual load of No. 4 buckshot and No. 1 buckshot. The Aguila is more expensive than the Federal load at $24.38 average for 20 shells. The reason the Aguila shell made such a wide pattern was that the heavier No. 1 buckshot went high over the No. 4 buckshot pattern. While we like the cohesive Federal pattern and higher energy, the Aguila never gave the initial problems with feeding the Federal did. The Aguila shell measured 1.5 inches unfired and 1.9 inches fired.

The Federal Shorty Shotshell is a 12-gauge 1¾-inch cartridge with 15 No. 4 buckshot pellets rated for 1200 fps. It was the most affordable at $11 per 10 shells. We saw the product on-line for $9 at one outlet. We were concerned with reliability after a false start with them in the 590S. The buckshot in this load averaged a 10-by-8-inch pattern at 10 yards and delivered more than 800 foot-pounds of energy. The Federal Shorty shell measured 1.4 inches in length unfired and 1¾ inches fired.

Next, there are six balls in the Firequest Shorty 00 Buck shotshell (Firequest.com), with three over the powder wad, then another wad, and then three balls below a wad beneath the crimp. There’s also a similar load with the six 00 balls situated together under the top and bottom wads (G25-059) and a third (G25-061) that has 12 No. 4 buckshot with two layers of six shot. The Firequest load provided impressive performance. Velocity is 1115 fps, and the load averaged less than 900 foot-pounds of muzzle energy. The pattern is a tight 3.5-by-5.5 inches. By any standard, the extra penetration of 00 buck and the tight pattern make the Firequest load a desirable option. However, the load is pricey, listing at $60 per 25. That is about $50 more than 20 Federal shells. Recoil and muzzle flash are limited. The load also performed well in standard 18.5-inch barrels. Feed reliability in a Remington 870 was a failure; we could not get the first one to chamber, much less feed. The Firequest shell started at an unfired length of 1.65 inches and wound up at a 1.8-inch fired overall length.

The Mason Munitions (MasonMunitions.com) load is affordable at $25 for 20 shells. Mason also offers a well-designed mini-shell adapter ($15) that’s similar to the better-known OpSol clip. This load uses eight No. 1 buckshot (30-caliber) shells, burns clean, and feeds as well as any other mini shell. The Mason starts out at an unfired length of 1.45 inches and finishes at a fired length of 1.5 inches.

The mini-shell adapter installation is pretty easy. Make sure gun is on Safe. Ensure the firearm is unloaded, with no shells in either the magazine tube or chamber. Slide the pump slide into its extended position. Squeeze and insert the back, flat end of the mini-shell adapter into the magazine loading port at an angle.

Push the rest of the adapter down into the magazine well so that it is flush to the rear and the bottom. Slowly rack the slide a few times to make sure that the mini-shell adapter is in the correct position. It should not move. If it does, remove the adapter and repeat steps one through three.

Here’s how the various shells fed and fired in these shotshell-chambered firearms.

Gun Tests Grade: C

$455

We first tested this model in the October 2017 issue, the first year the Shockwave was offered. It earned an A grade, with the review saying, “The Shockwave was like all Model 590 shotguns — built to last and well made. We’d opt for the OpSol Texas Mini-Clip and pack it with Aguila Mini Shells.” A 20-gauge Shockwave 50657 likewise earned an A, as did a .410 bore 50649, both reviewed in the March 2019 issue. However, they weren’t fired with shorty sub-gauge shells, since those didn’t exist until 2022.

We had on hand two 99% identical Shockwave firearms, the 590 and the 590S. The Mossberg 590 features a heavier barrel than the Mossberg 500, making it well suited to Shockwave configuration. The shotgun features synthetic furniture, a raptor-type firing grip, and a standard bead front sight. The receiver is red-dot sight compatible.

The trigger housing is polymer. The safety is the famous tang-mounted ambidextrous Mossberg type. Disassembly is easily accomplished by unscrewing the magazine tube cover and pulling apart the barrel from the receiver.

The safety of the 590 was stiff, even very stiff, and lightened up but little during the test. The action is markedly less smooth than the Remington’s, we felt. The tubular magazine holds five 2¾-inch shells.

The Shockwave firearms were loaded with a mix of 2¾-inch birdshot loads for familiarization. Mossberg recommends the Shockwave be fired from the hip. Raising the barrel to almost eye level invites a broken nose and/or a trip to the dentist. It is awkward to hold the Shockwave in any manner in which the bead is visible to the eye. All raters agreed a standard-stocked shotgun with an 18-inch barrel is much faster into action and leagues ahead in every firing course. The weight of the original Shockwave is well balanced.

With concentration on the proper hold and a firm grip, we were able to run the Shockwave reliably and get hits out to 5 yards under controlled range conditions. From the hip, it is true you have an excellent view of the field for fast reaction. The problem is getting a hit with the Shockwave. The drawbacks are many. A major problem is that the wrist cannot be locked when firing the Shockwave due to the Raptor grip. Next, we have only a two-point engagement, the forward and rear hands. The usual cheek weld is not possible. With the Shockwave-type shotgun, the forward and rear hands are not together as they are on a handgun and are not aligned with a cheek weld, as on a full-size shotgun. As a result, only a slight change in the position of either hand results in a miss.

We had difficulty in putting a full pattern on the target at 5 yards. Most raters fired high. These are experienced shotgunners, with two instructors in the crew, one police and one military. Opinions about the original Shockwave ranged from perhaps it would be useful for close-range home defense to useless. We all agreed that there is accountability for every round fired in home defense. The Shockwave makes hits very difficult to come by.

We tried a few of the mini shells and found reliability was poor. The shells would point out the bottom of the loading port during the firing cycle. We only got three consecutive shells to feed properly, and this was the best effort. All the shells did chamber properly if we got that far in the feed cycle. We tried to fire the Aguila during the combat firing test and were unimpressed.

To try to get the gun going, we moved to 2¾-inch shells and found Federal Ballisticlean cartridges with eight pellets of 00 frangible buckshot functioned fine, and with this training buckshot round, recoil was surprisingly not a problem. The Shockwave remained controllable. The shotgun was fired above hip level in a line with the pectoral muscles with a little better accuracy. The blast and flash with standard buckshot was awesome, and we felt it because the muzzle wasn’t that far ahead of our faces.

Our shooters had to consciously avoid aiming using the bead so as not to fire high. Some raters consistently fired into the cranial region of the B27 target at only 5 yards, even though they were trying for low center mass. Good we have a high berm at the firing range.

Our Team Said: The original Shockwave exhibited poor firing results as far as hit probability is concerned. Reliability with standard shells is flawless, but reliability with the all the shorties was flawed. The trigger at 7.0 pounds is manageable with a rapid reset.

The Bottom Line

After you read the sidebar reviewing the Black Aces Tactical Pro Series S Max, come back over here and read our conclusions on choosing a Shockwave-style firearm versus a short semi-auto or pump for home defense.

The logic of choosing a mini shell with about 50% of the energy of a standard buckshot load doesn’t make much sense to us. Better to learn to control recoil or use reduced-recoil buckshot loads that remain effective. Also, save in a single from-the-factory shotgun, the 590S, mini shells are unreliable in every short gun we’ve tested. Moreover, our team noticed some other issues:

Sacrificing a three-point hold on the shotshell firearms leads to misses. A slight movement of either hand on a Shockwave-style firearm results in an errant shot, which can create lifelong trouble.

There is no viable means of firing a Shockwave from cover.

Another serious concern is retention, which includes using leverage to free the shotgun from an attacker’s grasp and butt-stroke the adversary. This isn’t as feasible with the Shockwave.

Rapid reloads are problematic. It is difficult enough to practice quickly reloading the shotgun’s tubular magazine with the weak-side hand. During high-stress events, shooters often drop 2¾-inch shells. This results in many using the violin-type reloading drill, which uses the strong-side hand to reload the shotgun riding on the shoulder. Mini shells are extremely difficult to handle quickly using a standard or violin reload technique.

A folding stock or pistol grip shotgun isn’t as desirable as a fully stocked shotgun, but they remain well ahead of the Shockwave-type firearm. Yes, you could buy a 590 Shockwave and add an OpSol Mini Clip or Mason mini-shell adapter, but why? A regular shotgun with either a standard stock or a pistol grip stock, or both, as with the Black Aces shotgun, seems to be a better choice for most people.

Just the same, if your mind is made up and you must have one of the shotshell firearms, the Mossberg 590S Shockwave is an answer to many problems. As a boat gun for dispatching sharks at close quarters, or in a carefully considered home-defense situation for use at a few feet, or in an auto, where legal, the Shockwave has one overwhelming advantage over a pistol, and that is power.

If you own Mossberg 500 or 590 or the Maverick 88 shotguns and you want to fire mini shells for fun and practice, order the Mason Mini Shell Adapter or the OpSol clip. We find they work at least as well as the 590S, are affordable, and are easy retrofits. Just be certain your shells feed from all the firing positions you might encounter.

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