SSS.6.192 - Engaged Industries Operator 5.56 and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle (Free Version)
/Engaged Industries Operator 5.56 on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The Operator 5.56 is designed and manufactured by Engaged Industries. It is a 223 caliber centerfire rifle silencer, intended to suppress the 5.56x45mm cartridge with semiautomatic or fully automatic fire. The Operator 5.56 has a 1.5-inch diameter and is 6.375 inches long with the Stealth Lok QD mount installed; the mount may be attached to a variety of weapon systems threaded 1/2-28tpi. The Stealth Lok QD is a 6-lug-retained taper mount; it does not require user actuation of the secondary retention mechanism as the mechanism locally rotates and locks upon global system rotation. The tube of the silencer is constructed from titanium, whereas the baffles and mount are constructed from heat treated stainless steel. The silencer weighs 13.3 ounces and the Stealth Lok QD mount weighs 2.5 ounces, for a total system weight of 15.8 ounces, as tested. The Operator 5.56 can be obtained from Engaged Industries.
PEW Science is an independent private testing laboratory and also hosts the world’s only independent public suppressed small arms research cooperative. Testing, data analysis, and reporting is generated with funding provided by PEW Science members. Any test data that is generated with any portion of private funding contains this disclosure. The testing and analysis production for this Sound Signature Review was funded in part by PEW Science Project PEW-Engaged-107-001-25. Therefore, data pertaining to the Operator 5.56 in this Sound Signature Review is published with the express written permission of Engaged Industries LLC.
The testing and analysis presented in this Sound Signature Review is of the Engaged Industries Operator 5.56 mounted with the Stealth Lok QD muzzle device on the MK18 Automatic AR15 rifle rifle, chambered in 5.56x45mm NATO with a 10.3-inch barrel. Federal XM193 55gr ammunition was used in the test. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Section 6.192.1 contains Operator 5.56 test results and analysis.
Section 6.192.2 contains overall Suppression Rating comparisons of the Operator 5.56 with with dedicated 223 and 30 caliber silencers on the current market, including the Q Southpaw, Centurion Arms Maximus-L, Otter Creek Labs Infinity, PTR VENT Spiritus 556i, LMT AT ION LT, HUXWRX FLOW 556 Ti, Off Grid Operator Ti, Surefire SOCOM556-MINI2, KAC QDC/CRS-PRT, KAC QDC/MCQ-PRT, Surefire SOCOM556-RC3, Otter Creek Labs Polonium-30, AAC M4-2000 Mod 08, PTR VENT 3, SilencerCo Velos LBP, BOSS Guillotine, CAT WB, PWS BDE 556, CAT ODB, Aero Precision Lahar-30L, Lahar-30, HUXWRX FLOW 762 Ti, Maxim Defense DSX, Thunder Beast Dominus, KAC 5.56 QDC, CGS SCI-SIX, Dead Air Nomad-30, YHM Turbo T2, Dead Air Sandman-S, HUXWRX FLOW 556k, Energetic Armament ARX, KAC QDSS-NT4, Rugged Razor556, Otter Creek Labs Polonium and Polonium-K, Surefire SOCOM556-RC2, HUXWRX HX-QD 556 and HX-QD 556k, Q Trash Panda, CGS Helios QD, SilencerCo Saker 556, Rugged Razor762, and others.
Section 6.192.3 contains an article summary and PEW Science laboratory staff opinions.
Summary: When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Engaged Industries Operator 5.56 with the Stealth Lok QD mount achieved a composite Suppression Rating™ of 29.9 in PEW Science testing.
As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings.
6.192.1 Engaged Industries Operator 5.56 Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the Engaged Industries Operator 5.56 is shown in Table 1. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. The data acquired 0.15 m (6 in) right of the shooter’s ear is only available to membership supporters of PEW Science and the Silencer Sound Standard. You can support public PEW Science testing, research, and development with a membership, here. State-of-the-art public firearm sound signature testing and research conducted by PEW Science is supported by readers like you.
Table 1. Engaged Industries Operator 5.56 Sound Metric Summary
6.192.1.1 SOUND SIGNATURES AT THE MUZZLE
Real sound pressure histories from a 6-shot test acquired with PEW-SOFT™ are shown below. Six cartridges were loaded into the magazine, the fire control group positioned to single-shot, and the weapon was fired until the magazine was empty and the bolt locked back on the follower of the empty magazine. Only five shots are considered in the analysis. The signatures of Shot 6 are displayed in the data presentation but are not included in the analysis to maintain consistency with the overall PEW Science public dataset and bolt-closing signatures. The waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science laboratory sound signature testing is 1.0 MS/s (1 MHz). The peaks, shape, and time phasing (when the peaks occur in relation to absolute time and to each other) of these raw waveforms are the most accurate of any firearm silencer testing publicly available. PEW-SOFT data is acquired by PEW Science independent laboratory testing; the recognized industry leader in silencer sound research. For more information, please consult the Silencer Sound Standard.
The primary sound signature pressure histories for all 6 shots with the Engaged Industries Operator 5.56 with the Stealth Lok QD mount are shown in Figure 1a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 1b, in early time. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 2a. In Figure 2b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shots 2 and 3.
Fig 1a. Engaged Industries Operator 5.56 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. Engaged Industries Operator 5.56 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature
Figure 2a. Engaged Industries Operator 5.56 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. Engaged Industries Operator 5.56 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
The Engaged Industries Operator 5.56 possesses straight nested and notched cone baffles in a 1.5-in outer diameter design envelope. The first expansion (blast) chamber of the silencer is circumferentially ported along the majority of the primary baffle’s outer diameter, which reduces early time blast impulse accumulation. The annular vent allows for controlled blast load clearing off of the first reflector after expansion, that coupled with the traditional baffle design and dedicated bore for the cartridge, produces a relatively consistent signature and a moderate flow rate.
The following performance factors are observed in the above test data:
Blowdown duration is somewhat accelerated (Fig. 1a) with relatively typical early time blast load propagation (Fig. 1b).
FRP divergence is immediate in pressure space (Fig. 1b), as well as in impulse space (Fig. 2a). Accumulation rate mirrors post-FRP shots and peak accumulation does not significantly exceed that of subsequent shots (Fig. 2b).
Overall combustion propagation consistency is high and relatively controlled (Fig. 2a). Accumulation rate in (2) is elevated compared with most conventional baffle designs of similar size.
PEW Science Research Note 1: Engaged Industries has named the baffle system design in the Operator 5.56 “Vacuum Expansion Technology” that is intended to enable downstream restriction of expanding combustion gasses while maximizing early time flow rate. It appears that this behavioral balance has somewhat been achieved in the design, in accordance with observation (3) above. Further discussion is provided in Section 6.192.1.2 and Research Note 8 in the full Member Version of this report.
PEW Science Research Note 2: In the PEW Science Silencer Sound Standard research taxonomy, the Operator 5.56 somewhat meets the definition of a hybrid design, simply through the use of early time venting to reduce adverse blast load impulse accumulation in close proximity to the muzzle orifice. The baffle angle(s) are relatively steep. This type of early venting is in contrast with the geometry in the recently examined Q Southpaw (6.189). A larger diameter silencer, the Southpaw possesses significantly more initial expansion volume, but does not employ venting in the first expansion chamber, which prohibits expedient blast load clearing. The Q Southpaw therefore has lower early time flow rate (higher back pressure) than the Operator 5.56, despite being larger. In late time, the Q Southpaw is able to retain more combustion gasses for a longer period of time, and demonstrates this with a longer blowdown duration. However, the net average blast hazard decrease with the Southpaw is minimal; its muzzle (bystander) Suppression Rating is 29.8 compared with the Operator 5.56 muzzle Rating of 28.2. This difference in personnel hazard reduction is nominal.
PEW Science Research Note 3: Another interesting comparison between the two straight cone baffle silencers (unvented 1.75-in diameter Southpaw, and vented 1.5-in diameter Operator 5.56) is the first-round-pop (FRP) control. In the Q Southpaw impulse accumulation histories, early FRP divergence is noted with a significant rate increase, as well as an abrupt pressure rarefaction prior to peak accumulation. In contrast, the Engaged Industries Operator 5.56 maintains the same accumulation rate with consistent jetting through the entire history. The end result is a degree of FRP masking to bystanders despite early divergence, which is notable for such a simple design. FRP severity differentials are on the order of approximately 10 percent adjacent to the tested weapon system with this silencer.
PEW Science Research Note 4: It is extremely important for the reader to understand the Suppression Ratings are computed with free field test data, and are therefore universal when translating the weapon and operator to different environments without reflections. However, when the environment becomes complex with many reflecting surfaces, performance translation of different systems is not yet possible; sound field shapes and particle velocities result in varied blast wave time-of-arrivals, as well as changes of blast load angles of incidence; these variations change amplitude and phase waveform components. As a result of these inevitable environmental complexities, user impressions will vary, as both the shooter and bystander. Nonetheless, hazard reduction efficacy in the free field, as characterized by the Suppression Rating, holds. The Suppression Rating comparisons are the current state-of-the-art, and the most “apples to apples” sound suppression performance comparisons that currently exist. Further research is ongoing.
PEW Science Research Note 5: As in all semiautomatic AR15 weapon testing, a second pressure pulse originates from the ejection-port signature of the weapon and it occurs early enough in time such that its waves coalesce with that of the muzzle signature. However, in late time (at approximately 87 ms in Figure 1a) the mechanical noise of the bolt closing is observed. The pressure signature of Shot 6 does not display this event due to the bolt remaining open after the sixth and final round is fired from the magazine.
PEW Science Research Note 6: The closing time of the AR-15 bolt is directly related to the flow restriction of a silencer for a given weapon system. PEW Science has determined bolt closing time variation from the unsuppressed state to be a reliable indicator of silencer back pressure, with strong correlation with the PEW Science Back Pressure Metric, Omega and the alpha parameter. However, PEW Science has also determined that the indicator is unreliable upon upper receiver fouling. Sound signatures are not influenced by this fouling, as these kinematics occur in late time, after gas venting to atmosphere. Momentum transfer, weapon condition (upper receiver fouling), and other factors, can significantly influence bolt closing time. PEW Science urges the reader to exercise extreme caution if using the published bolt closing time to make determinations regarding silencer flow restriction (back pressure) or weapon system kinematics. This type of calculation may provide erroneous results, as the weapon condition at the time of each test is not published data. The time-scale duration showing bolt closing time is only published by PEW Science such that the signature data pedigree may be verified.
The shape, timing, and magnitudes of the early-time pressure pulses and overall shape of the impulse waveforms measured at the muzzle, from shot-to-shot, are relatively consistent. The consistency of the waveform amplitudes highlight the silencer’s overall sound performance consistency at the muzzle after the FRP, as well as the relative consistency of the tested automatic rifle firearm configuration.
As typically indicated, first-round sound signatures always differ from subsequent shots, as the atmosphere within the silencer changes. The FRP phenomenon cannot always be shown by viewing only the peak sound pressure. This is one of the reasons why The Silencer Sound Standard requires examining multiple sound signature metrics. Ammunition consistency can play a role in the determination of FRP, however, the close examination of measured pressure and impulse waveforms typically excludes ammunition from the possible factors influencing true FRP, due to the relative consistency of most high quality factory ammunition.
PEW Science Research Note 7: Note that the muzzle Suppression Rating of the Engaged Industries Operator 5.56 is 28.2 and the at-ear Suppression Rating is 23.6; the same zone on the Suppression Rating Dose Chart. The relatively low back pressure of the Operator 5.56 does contribute to a less severe ejection port blast signature, but the muzzle blast propagation from the silencer does somewhat increase shooter hazard on the standard MK18 weapon system. Weapon tuning will influence hazard reduction efficacy, and is outside the scope of this study.
The signatures measured at the shooter’s ear are presented and analyzed in the full Member Version of this report. Performance comparison with other silencers on the standard MK18 are provided below.
6.192.2 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 5 presents a comparison of the PEW Science Suppression Rating of the Engaged Industries Operator 5.56 with that of several other silencers on the MK18 weapon system. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Figure 5. Suppression Rating Comparisons of the Engaged Industries Operator 5.56 and other rifle silencers, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis
Figure 5 presents an overall summary of the postulated hazards to the operator and bystanders when fielding a variety of different silencers on the standard MK18 weapon system. The Engaged Industries Operator 5.56 from this test program is shown in red. Hazards are expressed with the Suppression Rating; a holistic parameter that captures human inner ear damage risk potential from a measured impulsive complex blast overpressure signature during the entire time regime of weapon operation, including combustion, complete blowdown, and all mechanical operation, including the carrier group returning to battery, in the true free field. The parameter may be used with the dose chart at the beginning of this report. The PEW Science Suppression Rating is a damage risk criterion (DRC), a lower Suppression Rating indicates a higher personnel hazard in the free field - it is not a subjective quantity; it is an objective quantification of hearing damage risk potential. Due to its true free field test data origin and complete waveform analytical calculation basis, it is the only known universal suppressed weapon system signature comparison metric available. Analytically computed metrics are color-coded in the Rankings Table and keyed to the dose chart for user interpretation.
The following gross conclusions can be made from the metrics presented in Figure 5, above:
The Engaged Industries Operator 5.56 produces free field bystander hazard reduction on par with that of the following silencers:
The free field operator (shooter) hazard reduction of the Engaged Industries Operator 5.56 with the standard untuned MK18 weapon system is somewhat lower than it is with other low(er) back pressure designs due to its more severe muzzle blast. The operator protection with the Operator 5.56 is on par with that of the:
Aero Precision Lahar-30 (again, though the Lahar-30 has higher back pressure than the Operator 5.56)
PEW Science Research Note 11: The Operator 5.56, for its size, exhibits relatively competitive performance. For the same (or lower) length and weight, the only silencers that outperform it in muzzle (bystander) Suppression Rating in the research pedigree are the previously mentioned Q Southpaw, Boss Silencers Guillotine (6.133), short PWS BDE 556 (6.123), and the Otter Creek Labs Polonium (6.75) and Polonium-K (6.95). Each of those five silencers have higher back pressure than the Operator 5.56, and all of them except for the Polonium series produce muzzle Suppression Ratings that are not significantly higher. In that respect, the overall performance of the Operator 5.56 is notable. There is a silencer in the MK18 research pedigree that is shorter and lighter than the Operator 5.56; the Energetic Armament ARX (6.82). However, the blast hazard protection performance of the ARX is significantly lower, particularly adjacent to the muzzle of the weapon system.
The hybrid design elements in the Operator 5.56, albeit minimal, do make a meaningful difference in performance as tested and analyzed, particularly for the weight and length envelope of the system. From more efficient stagnation relief, lower back pressure, and smaller size than silencers such as the Q Southpaw, the Operator 5.56 is an example of improvements to legacy baffle designs that can still show incremental improvement. It is possible that “Vacuum Expansion Technology” may be somewhat of a misnomer in that low or negative pressure regions have not been verified by testing; however, the silencer does produce low(er) back pressure than several competing designs.
As detailed in this report, signature at the operator’s head is a function of both muzzle and ejection port signatures from the AR-15 weapon system. Specific weapon system parameters will dictate modification efficacy.
Small arm weapon system suppression performance is a spectrum. The PEW Science Suppression Rating and the Silencer Sound Standard help quantify this spectrum for end users and industry, objectively.
6.192.3 Review Summary: Engaged Industries Operator 5.56 on the MK18 5.56x45mm AR15 with 10.3-in Barrel
When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Engaged Industries Operator 5.56 with the Stealth Lok QD mount achieved a composite Suppression Rating™ of 29.9 in PEW Science testing.
As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Laboratory Staff Opinion:
The Engaged Industries Operator 5.56 is a full length reduced diameter 5.56mm rifle silencer possessing a secondary retention mounting system that is simple to operate. The silencer also has lower back pressure than several competing models; the suppression performance of the silencer is relatively balanced, especially for its size and weight. Notable aspects of the silencer’s performance include its consistent signature and only moderate first-round-pop. At 1.5-in diameter, and less than 16 ounces including its mount system, the Operator 5.56 performance is relatively competitive in the broad 5.56 silencer market.
Engaged Industries produced a design in the Operator 5.56 system that is intended to enable downstream restriction of expanding combustion gasses while maximizing early time flow rate. It appears that that this balance has somewhat been achieved in the design, in accordance with the test data analyzed in this program. In the PEW Science Silencer Sound Standard research taxonomy, the Operator 5.56 somewhat meets the definition of a hybrid design, simply through the use of early time venting to reduce adverse blast load impulse accumulation in close proximity to the muzzle orifice. The baffle angle(s) are relatively steep. This type of early venting is in contrast with the geometry in the recently examined Q Southpaw. A larger diameter silencer, the Southpaw possesses significantly more initial expansion volume, but does not employ venting in the first expansion chamber, which prohibits expedient blast load clearing. The Q Southpaw therefore has lower early time flow rate (higher back pressure) than the Operator 5.56, despite being larger. In late time, the Q Southpaw is able to retain more combustion gasses for a longer period of time, and demonstrates this with a longer blowdown duration. However, the net average blast hazard decrease with the Southpaw is minimal; its muzzle (bystander) Suppression Rating is 29.8 compared with the Operator 5.56 muzzle Rating of 28.2. This difference in personnel hazard reduction is nominal. Another interesting comparison between the two straight cone baffle silencers (unvented 1.75-in diameter Southpaw, and vented 1.5-in diameter Operator 5.56) is the first-round-pop (FRP) control. In the Q Southpaw impulse accumulation histories, early FRP divergence is noted with a significant rate increase, as well as an abrupt pressure rarefaction prior to peak accumulation. In contrast, the Engaged Industries Operator 5.56 maintains the same accumulation rate with consistent jetting through the entire history. The end result is a degree of FRP masking to bystanders despite early divergence, which is notable for such a simple design. FRP severity differentials are on the order of approximately 10 percent adjacent to the tested weapon system with this silencer.
The Engaged Industries Operator 5.56 produces free field bystander hazard reduction on par with that of the HUXWRX (OSS) HX-QD 556, LMT AT ION LT, 556 End Cap, SilencerCo Velos LBP, Otter Creek Labs Polonium-30, YHM Turbo T2, Aero Precision Lahar-30, and WARCOMP-equipped Surefire SOCOM556-RC2. The free field operator (shooter) hazard reduction of the silencer with the standard untuned MK18 weapon system is somewhat lower than it is with other low(er) back pressure designs due to its more severe muzzle blast. The operator protection with the Operator 5.56 is on par with that of the Aero Precision Lahar-30, HUXWRX (OSS) HX-QD 556k, KAC QDSS-NT4, KAC 556 QDC/CRS-PRT, and Surefire SOCOM556-RC3.
The Stealth Lok QD mount is simple to operate. When the muzzle device is installed on the weapon system, the silencer may be rotated to tighten it to the device in the conventional (right-hand) direction. As the silencer is rotated, the secondary retention mechanism also rotates, retaining the 6 lugs on the muzzle device. Loosening of the silencer off of the device is accomplished by rotation in the opposite direction, which forces the secondary latch open and frees the muzzle device lugs.
PEW Science has not evaluated the durability of the Operator 5.56 silencer. The manufacturer of the silencer states that it is rated for any barrel length, and fully automatic fire for 100 rounds prior to requiring a cool down down period. The user is encouraged to contact the manufacturer for further information on durability metrics in accordance with their use case.
In this review, the Engaged Industries Operator 5.56 performance metrics depend upon suppressing a supersonic centerfire rifle cartridge on a short barrel gas-operated rifle, which is an incredibly difficult task. PEW Science encourages the reader to remain vigilant with regard to all supersonic centerfire rifle suppression claims. The gas volume and combustion products created by the firing of the supersonic 5.56x45mm cartridge are significant; the measured pressure and impulse magnitudes, and their durations, illustrate this fact. Silencer performance on automatic (reciprocating) rifles depends on many factors. Weapon configuration may significantly influence total suppressed small arm system performance.
The hearing damage potential of supersonic centerfire rifle use is significant. PEW Science encourages the reader to consider the Suppression Rating when deciding on an appropriate silencer and host weapon combination for their desired use.
