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: B

$536

The big question is how did Mossberg modify the 590 to feed mini shells successfully in the 590S? It isn’t that difficult because Mason offers a magazine port insert to cure feeding issues. The problem is the shotgun is then limited to mini shells. The competency in Mossberg engineering is that the company was able to design a shotgun that feeds both full-length shells and mini shells interchangeably.

They do that by redesigning the shell lifter. In the old-style 590 Shockwave reviewed above, the center of the lifter has a type of tab that feeds shells. That is no longer true in the 590S. Also, the 590S has a stamped plate that acts as a ramp or trunnion for bolt movement. This plate is attached to the action bars. Bolt tilt and movement locking and unlocking is affected by this part. This part is different from the 590. The 590S features what Mossberg has termed an energy-absorbing bumper in front of the trigger-assembly housing. Placing the shotgun upside down and observing the action as shells feed, it seems that a mini-shell-sized elevator space is created. Yet, function with full-length shells is retained.

We fired the 590S more than the others combined for several reasons. It didn’t take long to confirm the 590 Shockwave and Remington TAC-14 would not feed mini shells but they did feed standard shells. No use wasting the mini shotgun shells. On the other hand, the 590S has made claims to complete reliability with mini shells and full-length shells as well. We had to confirm this.

As it happened, the 590S is indeed mostly reliable. However, when attempting to test with the Federal Shorty, we racked the pump with the action upside down (you never know) and experienced failures to feed. A shotgun like the Black Aces will feed 2¾-inch shells upside down. The first full 590S magazine resulted in several failures to feed, reminiscent of the standard 590. Vigorously stroking the action, we were able to fire two magazines of the Federal Shortys without incident. Next, we cycled and fired 20 shells of the Aguila without incident. Also, the Mason and Firequest shells performed well.

Elsewhere, we had no more surprises. From the stabilizing strap on the fore end to the Raptor grip, handling was identical to the original 590.

Our Team Said: Save for a few inexplicable malfunctions in the beginning, the 590S Shockwave fed mini shells well. This ups the capacity of the 590S Shockwave from five to eight shells. Considering the shells exhibit no more recoil than birdshot loads in this firearm, there is some appeal. Because the 590S is useful with minis shells, we spent more time with this version. With firing limited to 5 yards, some of the raters got decent hits on the target. But those who managed hits practiced a lot, and all were much slower than with a standard-stocked shotgun.

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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