Defender Tactical minishell mini shell adapter
The Universal Minishell Adapter fits in Mossberg pump shotguns. (Travis Pike for TTAG)
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I’ve talked a lot about mini shells, and I’ve experimented with all the varieties I can get my hands on. I’m still trying to get my hands on some of the Mason Munitions No.1 mini shells, but they are continually sold out.

One of my biggest complaints about mini shells is compatibility. Recently Defender Tactical came to my attention, and their Universal Mini Shell Adapter seemed too good to be true. I reached out, and they agreed to send me one to test and review.

Defender Tactical sends the Universal Minishell Adapter with an aluminum follower. (Travis Pike for TTAG)

Adapters like the Opsol exist, and the Opsol is fantastic. The main problem with the Opsol, though, is that all you can shoot is mini shells when it’s installed. To shoot shells of other lengths, you had to move the adapter.

As most of us now know, mini shells come in a variety of sizes. Mossberg released the 590S series that eliminates the problem, but that means I have to purchase an entirely new shotgun.

Since I already own a number of Mossberg 500s, 590s, and Shockwaves, I wasn’t planning to buy a 590S series, especially when I could spend $25 and get an adapter that claims to do the exact same thing. And sure enough, the Defender Tactical Universal Minishell Adapter allows you to shoot any size shotgun shell from 3 inches to 1.75 inches without complaint.

Installing the Universal Minishell Adapter

Grab your Mossberg shotgun of choice and pop out the trigger retaining pin, hen remove the trigger. Inside the gun sits two grooves. The Universal Minishell Adapter slides into these grooves. It has a tongue, and the tongue faces downward. The little flapper is made of soft rubber that easily flexes.

Installation takes nothing more than a punch and about a minute. (Travis Pike for TTAG)

Defender Tactical includes a bright red aluminum follower. They say the setup is optimized for this follower. It’s also possible you won’t need to swap followers. I did because why keep a polymer follower when you have an aluminum model?

Pop the trigger out and slide the Univer Minishell Adapter in place. (Travis Pike for TTAG)

Installation takes about a minute. The soft rubber flapper is what ensures the shells are oriented correctly regardless of their length. The design flexes, so it moves out of the way to accommodate longer shells but provides enough extra length to keep the mini shells from bouncing around.

Defender Tactical produced a handy video showing how it’s done . . .

To The Range

I brought out all of my many minishells along with a few 3-inch magnum slugs and a variety of 2.75-inch shells. With the Universal Minishell Adapter locked in place, I hit the ground running.

I started by just loading the littlest fellas, the 1.75-inch shells, and working my way up to the 3-inch shells. From the little Federal and Aguila rounds to the big and mean 3-inch magnums, I had zero issues.

You can fit a bit of everything with the Universal Minishell Adapter. (Travis Pike for TTAG)

The gun fed and chambered and ejected every length of shell. I used the aforementioned 1.75-inch, 3-inch, and 2.75-inch shells alongside 2-inch and 2.5-inch shells. Every single one of them fed reliably.

After that, I mixed up the shells. I started going from smallest to largest, then reversed it. You can mix and match at will, and the Universal Minishell Adapter ate its way through any blend of shell lengths.

It’s almost silly how much the ammo varied in recoil and feel between shots. Feeling the poof of the 1.75-inch birdshot shell and then the thud of a 3-inch magnum slam into your is an interesting way to play redneck roulette with your shoulder.

All this fits in one magazine tube. (Travis Pike for TTAG)

I also tried a variety of 2.75-inch shells. Shell length is measured prior to crimping, so some 2.75-inch shells are longer than others. Rio and Monarch, for example, are a bit longer than Federal and Hornady. (Rio is long enough to reduce capacity by a round.) Even so, they all functioned fine and without any complaint.

Does It Get In the Way?

When you look at the Universal Minishell Adapter, it seems like it might get in your way for reloads. However, that isn’t the case. It moves out of the way and allows you to easily load the gun. The flexible design keeps it out of your way and doesn’t provide any additional challenges when it comes to reloading.

The Universal Minishell Adapter fits in Mossberg pump guns. (Travis Pike for TTAG)

I fired a total of 200 shells with the Minishell Adapter installed, mostly 2.75-inch birdshot and my crazy mix of mini shells. I had no reliability issues outside of a single 3-inch shell. For some reason, it wouldn’t load from the magazine to the chamber.

It turned out to be a shell issue, and a portion of the shell was flat. It was likely part of an experiment I did with leaving shotgun mags loaded for a year. It wouldn’t feed in any gun, so it wasn’t a problem with the Universal Minishell Adapter. This thing works flawlessly.

Specifications: Defender Tactical Universal Minishell Adapter

Compatibility – Mossberg 500/590 and Maverick 88
MSRP – $30.00 (on sale for $25 at this writing)

Ease of Use * * * * *
It drops in without a problem, and once it’s installed, you’ll forget it’s there.

Reliability * * * * *
From 3 to 1.75-inch shells, the little Universal Minishell Adapter cycles without complaint.

Value * * * * *
For $30, it’s well worth the investment if you like to shoot mini shells. It’s a bit more than the Opsol, but a helluva lot cheaper than the price of a new 590S shotgun.

Overall * * * *
The Defender Tactical Minishell Adapter just works. And it works for the piddling price of $30 (or less right now), letting you shoot anything you can load into your 3-inch chambered Mossberg pump gun. I can’t think of any reason not to have one installed in your Mossy pump. Go buy one.

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  1. I like the idea of 2.25″ buckshot shells for getting one additional load into my 6+1 and making it a 7+1 for potential indoor defense, but I’m not a fan of the much-ballyhooed Minis. Maybe for range fun, but the Minis don’t interest me.

    That being said, I’ve never seen anything other than the usual 2.75″ standard and 3″ or 3.25″ Magnums on any shelf. I once saw a box of Aguila Minis in a store, but that’s it. I’ve never seen 2.25″ in person, and I can’t buy online and have it shipped to me (at least, until Judge Benitez knocks down our ammo BGC law, too).

    • I still have a few 10 round boxes of Herters 2.25″ shells. They work. No after market adapter needed in a Maverick88. Wish they still made ’em but Cabelas kinda sux after they were bought by Bass Pro…

    • looks like one more thing i’ll have to buy….right now i’ve got the mossberg shockwave set-up for the mini’s…[with the side saddle you can mount nearly an entire box of shells (20 rds) in or on the gun] and the adapter…and my 88 set-up for regular shells and equipped with a laser…that means one gun is set-up for extremely close work and the other can reach out a the way, i’ve noticed quite a weight difference between the two…more steel in the shockwave?….

  2. I stocked up on Aguila mini shells years ago for my mossberg 590. And I got the Opsol adapter back then as well. I love it when the gun industry comes up with new technology. I’m going to have to get this new one!!!

  3. Definitely grabbing one.
    I’m still pissed Mossberg won’t sell a retrofit parts kit for their non “S” shotguns. I can’t imagine the receiver itself is any different.

    • Yup. I already have two shotguns. I’d be willing to spend money on a worthwhile upgrade to the ones I have- yes, I got an OpSol- but I’m not buying a third shotgun.

  4. I might get one despite the fact that mini shells are minimum 90 cents each these days. Another interesting option on the website is the safety button that has a rear sight built into it. it’s an Express sight that you can use with your front bead. That I think I will definitely get.

  5. When are shot shell manufacturers going to make mini-shells in 20 gauge? And when will Defender Tactical make this universal adapter for Mossberg 500 and 590 series shotguns chambered in 20 gauge?

  6. I like the option of mini-shells for reduced recoil. For almost any purpose a mini slug is still overkill. Having dramatically increased magazine capacity and significantly reduced recoil makes the Mossberg 500 viable for youth and smaller adults.

    It also makes reduced recoil introductory training with a 12 gauge possible. There are some government agencies that I will not name that do their new hires dirty by using the 12 gauge as their first long gun in training. Machismo and stupidity preclude using a cheaper 22 to develop a greater accuracy before introducing recoil.

  7. Air Force likes to train their rookies on the M-16 with a .22 rimfire adapter…easy to use on an indoor range…and we all know how the Air force likes to avoid the mud!…buddy of mine wound up with shrapnel in his arm because he refused to leave his bunk (for a trench) during a rocket/mortar attack……

  8. I got one for my new Shockwave. Works a charm. I’ve tested with a mix of shell sizes loaded simultaneously in the magazine, as well. Flawless!

    If you have a Shockwave, I also cannot recommend highly enough their Recoil Strap. It makes controlling the Shockwave a breeze. It makes gripping the Shockwave like putting on a glove.

    I’ve tricked out my Shockwave with all manner of Defender Tactical goodies, including the Highball front sight and rear Safety Sight. Also their overmolded forend grip. All are excellent in quality and at their prices, exceptional values.


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