Review: Thompson Machine Isis-2 Suppressor

Review: Thompson Machine Isis-2 Suppressor

The first thing we have to do is get past the model name. Isis? Hey, when the guys at Thompson Machine made and named that particular model, Isis was still just the ancient Egyptian goddess married to Osiris. The Egyptian pantheon is complicated, more than a little bizarre to modern sensibilities, and not at all connected to the ISIS you see in the news reports of today.

And from Thompson Machine, the Isis-2 is one heck of a good pistol-caliber suppressor.

Available in 9mm, 40 and .45, the Isis-2 is an improvement over their earlier Isis-1, which is a still-excellent suppressor from Thompson. The big deal with the "2" is the non-thread assembly. Well, the partial-thread, really.

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Thompson Machine, located in the picturesquely named town of Panacea, Fla., south of Tallahassee, makes the Isis-2, a first-rate pistol-caliber suppressor.

You see, the Isis-2 is a monocore design, with the core permanently attached to the rear cap. The rear cap and monocore slide into the tube, or shell, and the end of the monocore that goes in first is threaded, for the attachment of the muzzle plate.


The tube and monocore are made from 6061-T6 aluminum. Those of you who are heavy into rifle-caliber suppressors are looking at that and thinking "Hmmm, I'm not so sure about this." Relax. The uncorking pressure of even the hottest factory 9mm, out of the shortest barrel, is nothing close to what a rifle suppressor experiences.


And, unless you have one of the ultra-rare belt-fed 9mm select-fire SMGs out there, you aren't going to put enough ammo, in a short-enough time, through a pistol-caliber can to cause problems.


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The front cap is machined to a non-slip shape, so you can easily hand-tighten or unscrew it, providing, of course, you've kept the threads clean and clear.

There is also the little matter of mass. Remember, most handguns have to have the barrel pivot back and tilt down, in order for the mechanism to work. If you hang enough mass out on the muzzle, you can't get the pistol to work.

I agree that a stainless or Inconel handgun-caliber suppressor would be something marvelous, and would last forever, but you would be making your handgun a single-shot. Who wants that?

To make this short and sweet, aluminum is an entirely acceptable material to be making suppressors out of, if they are meant for handgun calibers.


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Sweeney installed a booster on the Isis-2, so it would properly cycle the Nighthawk host gun. It boosts the recoil to make up for the weight of the suppressor.

But back to the Isis-2. With the monocore inserted into the tube, the threaded front end of it now sits behind the front edge of the tube. You screw the muzzle cap onto the threads of the monocore itself, not into the tube or shell.

The muzzle cap has an interesting ridge on it, instead of being a smooth end cap, so you've got the traction you need to get it on and off. The front edge of the cap is machined as a continuous wave-form around its circumference. This provides a lot of traction for you to hand-tighten it.

The rear cap of the monocore, along with the front cap, traps and clamps the tube, and the tube itself is a simple cylinder of aluminum. An expensive, transfer-form approved cylinder, but still a cylinder without threads.


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The rear of the Isis-2 is threaded to accept any of a number of mounting systems. It's a standard and widely available thread pattern for many manufacturers.

The advantage to this is that if you get ham-handed, or something goes wrong and you mangle the threads, you do not have to send the serial-numbered part back for repair. You send the mangled parts, the monocoreand the muzzle cap, and those can be shipped, repaired and shipped back without a transfer application.

You may say "I'll never do that," but you should talk to someone who has previously neglected to disassemble and clean a handgun-caliber suppressor in time, and as a result carbon-welded it together.

While it is a problem, it isn't the problem, rather the attempts to get it apart become the problem. When frustrated, the use of various prying, levering and wrenching tools by owners becomes the means to wrecking a suppressor for the short-tempered. With the Isis-2 design, if you do end up knarfing things, the parts most likely to get butchered are the ones you can ship without asking "Mother, may I?"

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On the front end, the threads that connect the Isis-2 are on the end cap and the monocore, not the tube. That prevents wear and possible damage to the aluminum tube.

The rear cap is threaded internally for the mounting device or devices of your choice, and Thompson Machine was clever enough to make it a standard suppressor-mount thread, so you can use one of any of the usual suspects when it comes to pistol-caliber suppressor attachment.

You can install a booster for use on handguns. You can use a direct-thread cap, for use on a pistol-caliber carbine with a threaded muzzle. You can use a three-lug mount, for those of you lucky enough to have bought an MP5 before they became absurdly expensive. There's even the option of an Uzi-barrel mount.

Me, I stuck with the not-so-simple but common booster, since I intended to test it on various 9mm handguns. The booster, also known as a Nielsen device, stores energy and then delivers it back to the system to drive the pistol's cycle. This overcomes the problem of the extra weight of the suppressor, hung out on the end of the barrel, which would otherwise cause malfunctions.

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The Isis-2, showing the unthreaded tube, the monocore, the front cap and the booster. Keeping the tube in the form of a cylinder makes repairs a lot easier.

As the first host pistol I grabbed a Nighthawk 9mm set up for suppressors. It has a longer-than-the-slide threaded barrel, and the sights are taller, to "see" over the can.

Installation was simple; screw the booster into the back of the Isis-2, hand-tighten it, then take off the thread protector from the Nighthawk and screw on the Isis-2. Done.

As I don't have the metering system fully set up and wrung out yet, I wasn't able to do decibel measurements of the Isis-2. As a result, I could only go by my impression, but the impression I get from the Isis-2 is, "Wow." Now, just like any other, if you load your 9mm pistol with 95-grain screamers, going out the muzzle at 1300+ fps, you'll be making noise regardless of which suppressor you have on the muzzle.

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The Isis-2 accepts many of the various mounting systems you can use to attach it to a pistol-caliber firearm. This is the booster, to make it work on handguns.

Likewise, 147-grain subsonics will be a lot quieter. But when fed the subsonics, the Isis-2 is a quiet can. We can't do anything about the clack-clack of the slide going back and forth, but the actual muzzle report is definitely hearing-safe with subsonics.

Just as an aside, in a recent suppressor class, I was surprised to find that the bolt closing on an AR-15 is 120 dB all by itself. So unless we start re-building suppressor-ready firearms with rubber or synthetic bumpers inside, to soften the sounds of steel-on-steel, our self-loading firearms are going to have a certain level of unavoidable noise.

The Thompson Machine Isis-2 was not only quiet, but it was well-centered on the target and did not add to group size.

The range time I had to test the Isis-2 coincided with a winter storm, and 2 feet of snow and temperatures in the teens are not the best conditions for wringing out the last quarter-inch of group size. But when I can shoot consistent 3-inch groups at 25 yards, centered on the target, both with and without the suppressor, at 17 degrees, I'm happy.

And, since the monocore design of the Isis-2 makes it so easy to disassemble, I'll have no one to blame but myself if I ever forget, and carbon-weld the system together. If that happens, it will be cause for another column; how to disassemble a pistol suppressor without breaking it.

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