SSS.6.168 - HUXWRX FLOW 556 Ti and the M4A1 Mid-Gas 5.56x45mm 14.5-in Barrel Automatic AR15 Rifle
/HUXWRX FLOW 556 Ti on the M4A1 Mid-Gas 5.56x45mm AR15 with 14.5-in Barrel
The FLOW 556 Ti is designed and manufactured by HUXWRX. It is a 5.56 mm centerfire rifle silencer, intended to suppress the 5.56x45mm NATO cartridge, with no barrel length restrictions. It has a 1.8-inch diameter and is 6.75 inches long. The silencer mounts to proprietary HUXWRX LH-threaded taper-mount muzzle devices. With the muzzle device installed, the total length of the system is 6.9 inches. The entirety of the silencer is DMLS (3D-printed) Grade 5 Titanium. The silencer weighs 10.4 ounces and the Flash Hider-QD 556 taper mount weighs 3.3 ounces, for a total system weight of 13.7 ounces, as tested. The FLOW 556 Ti can be obtained from Silencer Shop.
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-HUX-088-001-24. Therefore, data pertaining to the FLOW 556 Ti in this Sound Signature Review is published with the express written permission of HUXWRX Safety Co. LLC.
! RESEARCH CAUTION !
It is important to note that higher distal gas velocity from HUXWRX Flow-Through designs produces low frequency-biased inner ear response. This signature characteristic is interpreted by bystanders and operators as sounding “boomy,” more so than that of silencers generating high flow rates through different methods. While such descriptors of sound signatures are subjective in nature, the phenomenon responsible for this impression has physical mechanism. This signature characteristic has been examined in-depth by PEW Science and analysis is published in Member Research Supplement 6.169 (Low Back Pressure 5.56 Rifle Silencer Head-to-Head Comparisons). Past Member Research Supplements 6.103 (5.56 NATO), 6.115 (7.62 NATO), and 6.124 (subsonic 300 BLK) are also available on the subject. All Member Research Supplements can be found here.
The testing and analysis presented in this Sound Signature Review are of the FLOW 556 Ti on the M4A1 Mid-Gas Automatic AR15 rifle, chambered in 5.56x45mm NATO with a 14.5-inch barrel. Federal XM193 55gr ammunition was used in the tests. The standard PEW Science M4A1 test host weapon system is described in Public Research Supplement 6.127.
Section 6.168.1 contains FLOW 556 Ti test results and analysis.
Section 6.168.2 contains overall gross Suppression Rating comparisons of the FLOW 556 Ti with other rifle silencers on the current market on the M4A1 Mid-Gas Rifle, including various configurations of the Surefire SOCOM556-MINI2, KAC QDC/CRS-PRT, KAC QDC/MCQ-PRT, CAT/WB/A1, and Surefire SOCOM556-RC2.
Section 6.168.3 contains an article summary and PEW Science laboratory staff opinions.
Summary: When paired with the 14.5-in barrel M4A1 and fired with Federal XM193, the HUXWRX FLOW 556 Ti achieved a composite Suppression Rating™ of 41.1 in PEW Science testing.
When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the HUXWRX FLOW 556 Ti achieved a composite Suppression Rating™ of 41.3 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
6.168.1 HUXWRX FLOW 556 Ti Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the HUXWRX FLOW 556 Ti is shown in Table 1. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. This is a members-only review and includes pressure and impulse waveforms measured at the shooter’s ear. PEW Science thanks you for your support; further testing, research, and development of PEW-SOFT and the Silencer Sound Standard is made possible by members like you!
Table 1. HUXWRX FLOW 556 Ti Sound Metric Summary
6.168.1.1 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 FLOW 556 Ti 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 Shot 2 and Shot 5.
Fig 1a. HUXWRX FLOW 556 Ti 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. HUXWRX FLOW 556 Ti 5.56x45mm NATO M4A1 Automatic Rifle Sound Pressure Signature
Figure 2a. HUXWRX FLOW 556 Ti 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. HUXWRX FLOW 556 Ti 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature
An in-depth examination of the 5.56x45mm NATO suppression performance of the HUXWRX FLOW 556 Ti is published in article 6.167 in which it was tested on the PEW Science standard MK18 weapon system. Much of the same discussion, performance analysis, and gross behavior of the silencer outlined in that test report also apply to the tested case herein. In this report, the same silencer with the same muzzle device were tested on the PEW Science standard M4A1 weapon system. The differences between the two weapon systems are:
Barrel length (the MK18 possesses a 10.3-in barrel, whereas the M4A1RIII possesses a 14.5-in barrel).
Gas system length (the MK18 has a carbine-length gas port location, whereas the M4A1RIII has a mid-length gas port location).
Gas port orifice size (the MK18 has a 0.070” diameter gas port, whereas the M4A1RIII gas port has a 0.076” diameter).
All three of the above characteristics change the performance of the gross suppressed small arm weapon system, with any rifle silencer. With regard to the HUXWRX FLOW 556 Ti specifically, the following performance attributes are observed in the above measured test data:
Similar to on the MK18, there is lower amplitude initial jetting on the M4A1RIII (Fig. 1b). Note that the gross pressure amplitudes are higher on the M4A1RIII than on the MK18 with this silencer.
Limited rarefaction, like the MK18, again with long duration gas throttle peaking in late time (Fig. 1b).
Somewhat more severe relative FRP divergence in both pressure space (Fig. 1) and impulse space (Fig. 2), but with lower absolute amplitude and duration.
Similar heat-affected momentum propagation increase later in the shot string as was demonstrated on the MK18 and demonstrated with all other HUXWRX rifle silencers (Fig. 2).
In general, the combustion propagation from the FLOW 556 Ti is somewhat more controlled on the M4A1RIII than it is on the MK18, and again more controlled than the other two HUXWRX silencer models on the MK18 (ref. Fig. 1b above, 6.83, and 6.114).
PEW Science Research Note 1: Like the previous generation HX-QD 762 series, silencers in the HUXWRX FLOW series contain a series of ported helical baffle components within the silencer core. Functionally, the core uses geometric features to induce turbulent flow, while early and continuously routing combustion gasses into annular space for down-stream venting to atmosphere. The distal end of the silencer contains significant exit flow area around its outer circumference. The sound suppression efficiency of this design is directly proportional to cartridge pressure, flow velocity, and duration. There are free field blast overpressures from the FLOW 556 Ti on the 14.5-in barrel system that are higher in peak values than from the 10.3-in barrel system. However, blast load impulse accumulation in the free field on the 14.5-in barrel system presents as lower. The Flow-Through technology, being sensitive to the varying input pressure of the two systems, loses some efficiency in peak pressure attenuation but is able to throttle the momentum accumulation more significantly. The 14.5-in barrel appears to place some of the primary accumulation in later time; the MK18 produces an initially more violent blast load jetting. The Flow-Through technology’s efficiency is therefore increased in early time, “truncating” the suppressed blast load peak. The impulse builds more gradually with the longer barrel system. This lowers immediate efficiency, but lengthens the jetting event. The net result of this overpressure increase and impulse decrease is an almost net balance in muzzle suppression. With a 40% increase in barrel length, the FLOW 556 Ti gross suppression performance at the muzzle only marginally increases from a bystander (muzzle) Suppression Rating of 40.4 to 40.7. This bystander hazard reduction is, essentially, unchanged for all practical purposes.
There are significant technical performance factors of note with regard to both the performance efficacy of HUXWRX Flow-Through technology, as well as regarding its comparison to some other technologies, namely hybrid variations. It is prudent to the repeat a major note from the previous MK18 evaluation report, below:
PEW Science Research Note 2: By their nature, Flow-Through silencers increase wave particle velocity from their distal ends; this is a consequence of the primary goal of reducing gross system backpressure; minimizing both their alpha early-time flow parameter and their Omega (6.40) late-time gas momentum accumulation rate. By minimizing the overall flow restriction downstream of the weapon muzzle, both weapon kinematic influence and hazards to the operator (blast overpressure and toxic gasses) may also be minimized. However, two physical phenomena present, consistently, through the use of this technology:
Higher distal gas velocity produces low frequency-biased inner ear response. This signature characteristic is interpreted by bystanders and operators as sounding “boomy,” more so than that of silencers generating high flow rates through different mechanism (including those using PTR PIP or CAT SURGE BYPASS). While such descriptors of sound signatures are subjective in nature, the phenomenon causing this impression has physical mechanism. This signature characteristic has been examined in-depth by PEW Science with analysis was previously published in Member Research Supplement 6.103 (supersonic 5.56 NATO), Supplement 6.115 (supersonic 7.62 NATO), and Supplement 6.124 (subsonic 300 BLK). To accompany this current study, Member Research Supplement 6.169 has been authored, to include examination of the subject FLOW 556 Ti.
As a consequence of both the phenomenon in (1) and pressure field shape from the distal vent array, blast load reflections may be perceived as more severe to both bystanders and the operator when fielding Flow-Through silencers. Although the Suppression Rating characterizes personnel risk at the instrumented test locations (MIL-STD muzzle and shooter’s ear), testing and analysis is performed in the true free field away from any reflecting surfaces other than the ground, which is 1.6 m below the weapon system muzzle. Bystanders and operator personnel may be located near berms, vehicles, structures, tree-lines, and other obstacles that act as reflecting surfaces. In these environments, it is likely that Flow-Through silencers and other silencers exhibiting the measured traits of low frequency-biased signatures presented in the above Research Supplements will present as “louder;” the already more noticeable late-time components of their signatures will be further exacerbated by the later-time wave reflection components of the total signature to which personnel are subjected. All weapon systems have more severe signatures near reflecting surfaces. However it is postulated that Flow-Through silencer signatures may be perceived as even more severe in these environments. Research is ongoing.
The above phenomena are one reason why fielding a CAT WB (6.130) on a 14.5-in weapon system may produce significantly different results to a FLOW 556 Ti in certain environments. As summarized in Section 6.168.2 of this report, both the bystander (muzzle) and operator (shooter) Suppression Ratings of the two silencers on this weapon system are very close. Therefore, their bystander and operator hazard reduction, if the weapon is operated in the true free field, are very close in efficacy. However, the two technologies manage pressure propagation extremely differently. In addition to not losing efficiency on the longer barrel system, the CAT WB produces blast load impulse throttle that has lower particle velocity; it has a lower distal flow rate. The aforementioned “boomy” nature of the signatures, the lower frequency inner ear response, and the severe obstacle reflections, are of less concern with the WB than they are with the FLOW 556 Ti. To iterate, in the true free field, their hazard reduction characteristics are extremely similar. The differential between personnel production in various environments is most likely higher with Flow-Through silencers than it is with SURGE Bypass silencers. This performance advantage is not limited to CAT SURGE BYPASS and is postulated to also be present with other hybrid technologies such as PTR PIP.
PEW Science Research Note 3: The first-round-pop (FRP) signature of the HUXWRX FLOW 556 Ti silencer on the 14.5-in barrel M4A1, to bystanders, relative to subsequent shots, is somewhat similar to that on the 10.3-in barrel MK18. This is a direct result of the net muzzle suppression balance described in Research Note 1.
PEW Science Research Note 4: As discussed in Research Note 14 of the FLOW 556 Ti MK18 test report, as is the case with hybrid designs, Flow-Through technology can still not completely alleviate increased hazards on weapon systems in which the gas system delivers increased blast impulse in the unsuppressed state. The increased dwell time and gas port orifice size of the mid-length gas Daniel Defense 14.5-in barrel system create a more hazardous ejection port blast environment for the weapon operator. This is further discussed in the shooter’s ear data and analysis presentation in Section 6.168.1.2.
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 90 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 AR15 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 FLOW 556 Ti is 40.7 and the at-ear Suppression Rating is 27.6; different zones on the Suppression Rating Dose Chart. The lower back pressure of the FLOW 556 Ti contributes to a less severe ejection port blast signature. The back pressure is low enough to reduce the ejection port blast loads to the shooter more significantly than with many other silencers on the standard M4A1 weapon system. However, as discussed above, the M4A1RIII produces more severe ejection port blast hazard than the MK18, in the unsuppressed state.
The signatures measured at the shooter’s ear are presented below.
6.168.1.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 6-shot test acquired with PEW-SOFT at the shooter’s ear are shown below. Again, the waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz).
The primary sound signature pressure histories at the ear for all 6 shots are shown in Figure 3. The primary sound signature history is shown in Figure 3a. An annotated timescale is displayed in Figure 3b, for Shots 1 and 2. The real sound impulse (momentum transfer potential) histories at the ear from the same 6-shot test are shown in Figure 4. Again, full and short timescales are shown.
Figure 3a. HUXWRX FLOW 556 Ti 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature
Figure 3b. HUXWRX FLOW 556 Ti 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 4a. HUXWRX FLOW 556 Ti 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature
Figure 4b. HUXWRX FLOW 556 Ti 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature Peaks
As expected, the blast pressure and impulse measured at the shooter’s head indicate the FLOW 556 Ti is achieving a very high level of operator protection. The blowdown speed is significant and clear, definitive ejection port blast reduction indicators are present. As previously discussed in article 6.167, in systems in which ejection port blast is greatly diminished, the FRP generation at the shooter’s head, in impulse space, will present as “front-loaded.” This is evident in Figure 4b. However, this phenomenon is more limited than observed in the MK18 testing of the same silencer. The ejection port blast from the M4A1RIII is simply more severe; it is not possible for the FRP impulse to present as fully decoupled in early time.
PEW Science Research Note 7: It is likely that the Daniel Defense M4A1RIII weapon system, as fielded, is “over-gassed”. Although this type of weapon parameter trait can increase reliability of the system in adverse conditions (e.g. lacking lubrication, use of weaker ammunition, debris inference in the reciprocating system, etc.) it is undesirable from a pure blast overpressure reduction standpoint, to the weapon operator. The primary benefit of a HUXWRX Flow-Through silencer is being able to maintain unsuppressed system behavior while suppressed; this allows for less modification to the systems, high reliability, and less user-error when fielding. However, when a system is already “over-gassed,” less hazard reduction may be noted. The FLOW 556 Ti still provides exceptional ejection port blast hazard reduction on this weapon system. However, its combined efficiency losses with lower muzzle pressure and the over-gassed host result in a net shooter’s ear Suppression Rating that is only marginally different than that of the CAT WB on this weapon system; a smaller silencer that had lower Suppression Rating potential on the MK18. The CAT WB increases in performance efficiency on the longer barrel, while still having a high enough early time flow rate to mitigate ejection port blast hazards on the over-gassed system.
Nonetheless, as discussed in the MK18 test report, operator hazard reduction is a function of all system parameters. It is also important to note that the above discusses only blast overpressure hazard reduction. Gas toxicity hazards, even if reduced by weapon tuning, will most likely not be reduced to the lower levels of FLOW 556 Ti use with many other silencers, for example. This is particularly the case with rapid fire weapon operation, etc, in which the environment for expanding combustion gasses in the silencer becomes super-heated and downstream expansion is limited. This is sometimes colloquially referred to as the “gas stack” phenomenon.
PEW Science Research Note 8: There are almost no heat-driven performance differentials throughout the shot string measured at the operator’s head, compared to at the muzzle, with this silencer on both the M4A1RIII or MK18 (ref. Research Note 11, 6.167). This is further exacerbated in the M4A1RIII test here by the severe ejection port blast of the host weapon.
The HUXWRX FLOW 556 Ti presents an extremely “balanced” shooter’s ear signature on this weapon system, when considering the contributions from both muzzle blast and ejection port blast to the hazard.
Gross hazards and behaviors with the M4A1 weapon system are compared in the following section.
6.168.2 Suppression Rating Comparison (5.56x45mm from the M4A1)
Figure 5 presents a comparison of the PEW Science Suppression Ratings of the HUXWRX FLOW 556 Ti with that of other rifle silencers on the M4A1 weapon system. The standard PEW Science M4A1 test host weapon system is described in Public Research Supplement 6.127. As PEW Science research with the M4A1 system continues, the dataset will be further populated.
Figure 5. Suppression Rating Comparisons of the HUXWRX FLOW 556 Ti, KAC QDC/CRS-PRT, KAC QDC/MCQ-PRT, Surefire SOCOM556-MIN2, CAT WB, and SOCOM556-RC2 with different mounts, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis
Figure 11 presents an overall summary of the postulated hazards to the operator and bystanders when fielding a HUXWRX FLOW 556 Ti on the M4A1 weapon system. Data is also presented for the fielding case of the Surefire SOCOM556-RC2 (6.128), SOCOM556-MINI2 (6.144), and KAC QDC PRT units (6.156) on different muzzle devices, along with fielding of the CAT WB (6.130). Hazards are expressed with the Suppression Rating; a holistic parameter that captures human inner ear damage risk potential from a measured impulsive complex 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.
The following gross conclusions can be made from the above:
The HUXWRX FLOW 556 Ti achieves comparable hazard reduction to bystanders, in the free field, to the CAT WB on the standard untuned M4A1RIII weapon system. This occurs despite the higher performance of the FLOW 556 Ti on the short barrel MK18; this is due to efficiency loss factors discussed in Research Note 1, along with host factors discussed in Research Note 4.
The free field operator (shooter) hazard reduction with the FLOW 556 Ti on the standard untuned M4A1RIII weapon system is also on par with that of the CAT WB. Again, this is somewhat due to host factors previously discussed. The M4A1RIII is an “over-gassed” rifle. Significant hazard reduction efficacy is extremely difficult to achieve without weapon modification. Nonetheless, it is important to note that the mechanisms by which the operator hazard reduction on the standard untuned M4A1RIII is achieved with the Flow-Through technology in the HUXWRX silencers and the SURGE BYPASS hybrid technology in the CAT WB is different. The waveform parameters vary significantly as a result, and the Suppression Rating allows one to distill the overall severity into a single metric for free field hazard prediction. As discussed published with in-depth analysis in Member Research Supplement 6.169 on the MK18, specific signature attributes and environmental factors can and will influence user perception and experience.
The Surefire SOCOM556-RC2 with the 3-Prong flash hider provides relatively high hazard reduction for both the operator and bystanders when compared to several other systems. The RC2 uses a legacy version of Surefire Total Signature Reduction hybrid technology and it does pay dividends with this system.
The performance gap between the two extremes of suppressed systems displayed in the current M4A1 dataset is significant; the difference in signature severity produced by the FLOW 556 Ti and CAT WB on this weapon system, compared with that of a WARCOMP-equipped SOCOM556-MINI2, for example, is pronounced. The performance of a MAMS-equipped KAC 556 QDC/MCQ-PRT produces significantly higher blast load hazard reduction to both bystanders and the weapon operator.
Increased gross flow rate (lower back pressure) does pay dividends in ejection port blast hazard reduction to the 14.5-in barrel M4A1 midgas weapon operator, but without weapon modification, shooter’s ear protection levels may plateau.
As detailed in this report, the Suppression Rating at the shooter’s ear may be significantly influenced by the ejection port signature from an AR15; all other things equal. For details on performance increases that are possible when “tuning” an AR-15 weapon system for a silencer, please see Review 6.111. It is important to note that not all silencers will possess a significant increase in shooter’s ear Suppression Rating from weapon tuning. 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.
6.168.3 Review Summary: HUXWRX FLOW 556 Ti on the M4A1 Mid-Gas 5.56x45mm AR15 with 14.5-in Barrel
When paired with the 14.5-in barrel M4A1 and fired with Federal XM193, the HUXWRX FLOW 556 Ti achieved a composite Suppression Rating™ of 41.1 in PEW Science testing.
When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the HUXWRX FLOW 556 Ti achieved a composite Suppression Rating™ of 41.3 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 HUXWRX FLOW 556 Ti is a lightweight full size 5.56 mm rifle silencer with significant back pressure reduction, without compromise of gross sound suppression performance. Optimized for the 5.56 mm cartridge, the FLOW 556 Ti improves upon the performance of the FLOW 762 Ti on AR15 weapon systems in both bystander and operator hazard reduction. At less than 14 ounces of system weight, its performance and maneuverability are significantly notable. Acute blast overpressure hazards from the ejection port of standard AR15 systems are significantly reduced through the use of this silencer. The silencer is constructed of 3D-printed Grade 5 Titanium. The Flow-Through technology implemented in the FLOW series from HUXWRX continues to represent one of the most advanced systems evaluated by PEW Science, to date.
Like the previous generation HX-QD 762 series, silencers in the HUXWRX FLOW series contain a series of ported helical baffle components within the silencer core. Functionally, the core uses geometric features to induce turbulent flow, while early and continuously routing combustion gasses into annular space for down-stream venting to atmosphere. The distal end of the silencer contains significant exit flow area around its outer circumference. The sound suppression efficiency of this design is directly proportional to cartridge pressure, flow velocity, and duration. The FLOW technology, taking advantage of additive manufacturing (3D-printing), is more advanced than that of the previous generation HX-QD series and the measured performance illustrates this advancement.
The FLOW 556 Ti removes the over-bore compromise from the FLOW 762 Ti. Externally, the design envelope of the two silencers is identical, with the FLOW 556 Ti weighing one ounce less than the 762 model. Internally, the design has been optimized for the 5.56x45mm cartridge. Therefore, the FLOW 556 Ti may be considered the full-size version of the FLOW 556k, but constructed from titanium instead of Inconel alloy. All three silencers use the same mounting system and all testing was performed with the same flash hider mount.
In contrast with its performance on the untuned standard MK18 weapon system, the FLOW 556 Ti bystander and operator hazard reduction on the 14.5-in M4A1RIII, in the free field, is similar to that of high performing competing models like the CAT WB. The performance gap closes due to efficiency factors of the Flow-Through technology discussed herein, along with host weapon factors. Nonetheless, the FLOW 556 Ti hazard reduction has an extremely high level of efficacy. However, again, when moving to environments other than the free field, including those in which berms, tree lines, vehicles, and structures are present, silencers with HUXWRX Flow-Through technology may produce more severe user perception. A function of both wave particle velocity and field shape, this phenomenon is a pervasive performance attribute. Nonetheless, gas momentum rate throttling with silencers such as the FLOW 556 Ti and FLOW 762 Ti, when compared to shorter implementations in the FLOW 556K, does offer somewhat of a severity reduction. Low frequency inner ear response bias does remain, as reported and analyzed in detail in Member Research Supplement 6.169 for the shorter barrel MK18 system.
One consequence of high mass flow rate through a silencer is a potential increase in flash signature. However, the FLOW series silencers possesses flash-hiding features on their endcaps and increased internal surface roughness through additive manufacturing, compared with the previous generation HX-QD series. PEW Science postulates that these design factors influence flash suppression performance, but has not yet evaluated the flash hiding performance of the FLOW 556 Ti. Qualitative measurements of flash using the FLOW 556K on short barrel 5.56x45mm weapons have indicated adequate flash suppression for lab personnel. Qualitative measurements of flash using the FLOW 762 Ti on short barrel 7.62x51mm weapons have also indicated adequate flash suppression for lab personnel, albeit with some sparking.
The left-hand (LH) threaded taper mounts from HUXWRX are simple to operate. They may be installed on the weapon system with an adjustable wrench. As the silencer is LH threaded to the mount, the mount is easily removed from the silencer, should the mount be detached from the weapon while still in the silencer. One can then tighten the entire assembly to the conventionally right-hand (RH) threaded barrel muzzle, and continued RH tightening will subsequently loosen the silencer from the mount. Although proper mount installation torque mitigates such a solution from being absolutely necessary, this mechanical feature is welcome for practicality. The distal vents of the silencer produce thrust which actively tighten the silencer to the mount, during use. This feature is unique to HUXWRX rifle silencers; PEW Science confirms that this feature demonstrates efficacy in the field.
PEW Science has not evaluated the durability of the FLOW silencer system(s) on semiautomatic or automatic host weapons. Note that the nature of low flow restriction (low back pressure) silencers may positively influence durability, as the silencers are designed to vent more quickly than traditional designs, relative to the time regime of combustion. As the FLOW 556 Ti is 3D-printed in its entirety, PEW Science postulates that it may exhibit increased durability when compared to the previous HX-QD generation. These phenomena are subjects of further research. HUXWRX reports this postulation to be correct, in accordance with their internal testing.
In this review, the HUXWRX FLOW 556 Ti performance metrics depend upon suppressing a supersonic centerfire rifle cartridge on a commonly fielded 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.
