Testing and Evaluation

By Al Paulson

Gemtech’s Predator Suppressor

The realm of rifle suppressor design has matured considerably in recent years with the growing popularity of compact variants of the M16 rifle among both the law-enforcement community and military SpecOps units. The M4A1 carbine, in particular, has proved well suited to entry and CQB (Close Quarter Battle) applications, where a more compact and practical sound suppressor would pay substantial tactical dividends for many missions. The Navy stimulated the recent jump in technology by publishing an RFP (Request for Proposals) for a robust, high-performance suppressor for the M4A1 carbine that would include a quick-mount that would attach to the M4A1’s flash hider or a clone of the flash hider. This article will evaluate the design and performance of the Predator suppressor, which is a spin-off of Gemtech’s quest to enter the competition at the Naval Surface Warfare Center in Crane, Indiana.

The Gemtech design team of Dr. Phil Dater, Greg Latka, and Jim Ryan approached the Navy requirements as a three-pronged R&D effort. Dater led the work on a suppressor design. Ryan and Mark Weis ramrodded the cumbersome contractual and specifications requirements. Latka led a simultaneous effort in Michigan to develop a suitable quick mount based upon his patented Tri-Lock system. Separating the effort into three simultaneous projects enabled Gemtech to hit the ground running in their attempt to develop a quantum jump in technology to meet the very ambitious Navy wish list and time constraints.

Despite the nominal separation of the effort, everyone on the Gemtech team did contribute to all three projects whenever an individual’s particular expertise was needed. It was the depth and breadth of expertise brought to the table by every member of the design team, plus a willingness to play to each individual’s unique strengths on a daily basis, that gave the team a remarkable esprit de corps and enabled them to develop a lot of new technology in a very short time. They called their new navspec suppressor with spring-loaded quick mount the M4-96D. They simultaneously developed a more economical variant of the M4-96D for the civilian market. Originally called the M4-96C and now called the Predator, this civilianized suppressor is fabricated from the same materials and uses the same internal design as the M4-96D. The only difference is that the Predator features a 1/2×28 TPI threaded mount instead of Gemtech’s snap-on Bi-Lock mount. Thus, the Predator is also a bit shorter and lighter than the M4-96D, as well as $145 cheaper.

Suppressor Design

The Navy RFP stipulated a maximum acceptable suppressor weight of 26 ounces (737 grams) and an ideal weight of 16 ounces (454 g). The can should have a maximum diameter of 1.75 inches (4.4 cm), with a preferred diameter of 1.4 inches (3.6 cm). And, finally, the new suppressor should have a maximum length of 8.0 inches (20.3 cm) with a preferred length of 6.3 inches (16.0 cm).

The M4-96D is 7.75 inches (19.7 cm) long and 1.5 inches (3.8 cm) in diameter, and the suppressor weighs 24.7 ounces (700 g). All suppressor components are coated in a matte black oxide, and the interface piston receives an additional coating of Sandstrom Products 9A Dry Film Lubricant to enhance corrosion resistance.

The Predator developed by the Gemtech team is 6.2 inches (15.7 cm) long with a diameter of 1.5 inches (3.8 cm). It weighs 20 ounces (680 grams). Clearly, both Gemtech cans have an envelope and weight that fall well within the Navy specs. From a subjective point of view, the relatively modest length and weight of both the M4-96D and the Predator give the suppressors excellent handling characteristics on any member of the AR15/M16 family of weapons. Both suppressors are especially handy when mounted on an M4A1 or CAR-15.

The Predator and M4-96D are both fabricated from 300 and 400 series stainless steels, and feature an improbably small number of baffles: three. These complex baffles of three different designs feature asymmetric geometries that work the combustion gases very hard without adversely affecting accuracy. Since the Navy had a very ambitious requirement for sustaining full-auto fire, Gemtech developed a blast baffle at the rear of the baffle stack made from Inconel. Inconel is particularly resistant to both heat and the erosive effects of hot combustion gases, and this quality is essential if the suppressor will be subjected to full-auto fire. The use of Inconel provides durability that would have been unthinkable several years ago. While the Predator is slightly shorter and lighter than the M4-96D, as a practical matter both provide the same durability and handiness. But how quiet are they?

Sound Reduction

I conducted sound testing employing the specific equipment and testing protocol advocated at the end of Chapter 5 in the book Silencer History and Performance. The microphone was placed 1.00 meter to the left of the suppressor or muzzle according to U.S. Army testing procedures specified in MIL-STD-1474C. The ambient temperature during the testing was 50øF (10øC). Velocities were measured in feet per second using a P.A.C.T. MKIV timer/chronograph with MKV skyscreens set 24.0 inches apart and the start screen 8.0 feet from the muzzle. The speed of sound during the testing was 1,107 fps (337 mps).

Two kinds of ammunition were tested using an M4A1 carbine with 14.5 inch (36.8 cm) barrel with 1 in 9 rate of twist as the test weapon: M855 ball ammunition and an experimental lot of 5.56x45mm subsonic rounds being developed by Whit Engel of Engel Ballistics Research. These White Tip rounds were developed with 55 grain (3.56 gram) projectiles for 1 in 9 barrel twists and 62 grain (4.03 gram) projectiles for 1 in 7 barrels twists. I used the former for this testing.

The Engel ammunition is intended for maximum stealth, and therefore does not cycle the action. With the mechanical clatter and the ballistic crack eliminated, the silenced M4 carbine with subsonic ammunition subsequently proved deadly on a community of ground squirrels. An improved version of this subsonic 5.56x45mm ammunition will be available commercially by the time you read this. Featuring a moly-coated 53 grain (3.45 gram) flat-base match Sierra bullet, the new round from Engel Ballistics Research is reportedly more accurate and a bit quieter.

The performance of the Predator was compared side by side with one of the great 5.56mm suppressors of all time, a 1994 vintage HRT from AWC Systems Technology. Constructed entirely of 304 stainless steel, measuring 6.5 inches (16.5 cm) long with a diameter of 1.5 inches (3.8 cm), the HRT was finished in a matte black textured powder coating. The M4-96D with Bi-Lock mount was also tested as was a new Gemtech P90 suppressor for the FN P90 Personal Defense Weapon. Although the P90 PDW uses the diminutive Five-seveN (5.7x28mm) cartridge, I test fired Gemtech’s prototype P90 suppressor on the M4A1 using full-powered M855 ball… a real trial by ordeal. Together, these results promised to provide some interesting insights into several important new technologies.

The data of suppressed and unsuppressed sound signatures in Table 1 represent the mean (average) value of at least 10 shots. Table 2 provides the net sound reductions, which provide a more useful measure for comparing the performance of suppressors tested on different days or on different weapons. Figures 1-3 compare the external ballistics of the M855 and White Tip subsonic rounds. The Navy required that competitors achieve at least a 25 dB net sound reduction using M855 ball ammunition as measured 1 meter from the left of the muzzle, with a design goal of at least a 30 decibel reduction. The Gemtech Predator suppressor met the Navy’s minimum sound suppression goals using M855 ball and came within 3 dB of meeting the Navy’s wish list goal of a 30 dB reduction. Remarkably, addition of the Bi-Lock quick-mount to Predator (to make a new model called the M4-96D) improved the suppressor performance enough to meet the Navy’s design goal of a 30 dB reduction. The M4-96D was 3 dB quieter than Gemtech’s Predator and 2 dB quieter than AWC’s HRT.

Gemtech’s Predator provides an unusually small solution for suppressing compact variants of the M-16 rifle. (*Dr. Philip H. Dater Photographer*)

Furthermore, the Predator was within 1 decibel as quiet as the outstanding HRT suppressor from AWC Systems Technology despite the fact that it is smaller and lighter and hundreds of dollars less expensive. The M4-96D is quieter than the HRT, has a superior mounting system, should be more durable when subjected to full-auto fire (thanks to Gemtech’s Inconel blast baffle), and retails for about the same as the wholesale price of the HRT. Gemtech’s Predator and M4-96D not only provide superior overall technology to the HRT, they do so at a better price. Getting more for less is downright compelling.

Then there is the performance of P90 suppressor, which was as quiet on an M4A1 as the Predator despite the fact that the P90 can was designed for a much smaller cartridge.

Finally, we should examine the phenomenon of first-round pop, which is produced when powder residue and secondary combustion gases combine with oxygen in the suppressor. Minimizing first-round pop can have tactical or social implications if only one round is required and that cold shot is too loud. Virtually eliminating first-round pop requires considerable design prowess. I was impressed that the Predator’s first-round pop averaged +3.1 dB over the course of the testing; some rifle suppressors generate a first-round signature as much as 6-10 decibels louder than the second shot. Adding the Bi-Lock mount to transform the Predator into the M4-96D reduces the FRP to just 0.8 dB. Gemtech’s P90 suppressor, which was designed for the much lower gas volume produced by the 5.7x28mm cartridge, produced a very low first-round pop of +1.1 dB. Clearly, Gemtech’s P90 suppressor merits its own in-depth evaluation. AWC’s HRT also performed well in this category, producing a respectable FRP of +1.7 dB.

A diagonal close-up of the Predator shows its distinctive radial pattern of assembly holes on this sealed unit, which is cleaned by immersion.
(*Dr. Philip H. Dater Photographer*)

These suppressors became very stealthy indeed when employed with subsonic ammunition, producing sound signatures that were dramatically below an MP5 SD and even well below commonly encountered integrally suppressed .22 rimfire rifles. Even jaded suppressor cognoscenti found it hard not to giggle the first time they fired these suppressors with Engel subsonic ammunition. As the accompanying figures show, the trajectory and bullet drop produced by the subsonic ammunition suggest that subsonic rounds will be difficult to place accurately at long range. When employed tactically, these rounds should probably be limited to an effective range of 80 yards (73 meters) to ensure reliable CNS (Central Nervous System) hits on a man-sized target.

Conclusions

Subjectively, the Gemtech Predator sounds almost indistinguishable from the AWC HRT, which is an outstanding suppressor. Yet the Predator, is smaller, lighter, and cheaper. The Gemtech M4-96D has a much better mounting system than either the Predator or HRT. The M4-96D snaps on and off and will return to the same zero every time the suppressor is mounted. Most important of all, the Bi-Lock mount will not loosen during firing. Thread-mount suppressors for the AR15/M16 are notorious for loosening during prolonged firing, which can adversely affect accuracy if not corrected. Since the M4-96D is only $145 more than the Predator—and since the M4-96D is cheaper and quieter and presumably more durable than the HRT—the conclusion seems to be a no-brainer for the tactical user: the Gemtech M4-96D is the only logical choice, in my opinion.

With such an outstanding and affordable product as the M4-96D suppressor with Bi-Lock mount in Gemtech’s stable, I have to ask a rather rude question. Why even bother making the Predator?

The only application where I would consider using the Predator would be on bolt-action varmint rifles where size and weight (or cost) might be factors. I have a tiny single shot .22 Hornet that would be well suited to the Predator. But for sporting or tactical use with a semiautomatic or full-auto rifle or carbine, I’d choose the M4-96D over the Predator every time.

The Predator and the M4-96D with Bi-Lock mount were developed in just four weeks, enabling Gemtech to submit the M4-96D suppressor to the Naval Surface Warfare Center within the time constraints stipulated in the RFP. This represents a significant improvement in the state of the art in an unbelievably short time. No wonder SAR Technical Editor Dan Shea has referred to the Gemtech design team of Phil Dater, Greg Latka, and Jim Ryan as the “Dream Team.”

Both the Predator (with its 1/2×28 TPI threaded mount) and the M4-96D (with its snap-on mount and proprietary replacement flash hider) are now available commercially. Government agencies and qualified U.S. residents can write Gemtech. Catalogs are $5 unless requested on agency letterhead. Gemtech also has a site on the World Wide Web (the URL is http://www.gem-tech.com).