SSS.6.231 - LayerX Strake 9 and the Heckler and Koch SP5 9x19mm Subgun (Free Version)
/LayerX Strake 9 on the HK SP5 9x19mm Subgun with 8.9-in barrel
The Strake 9 is designed by LayerX. It is a compact 36 caliber subgun silencer, intended to suppress many cartridges with projectiles appropriately sized to travel through the bore, including 5.56 NATO and .308 WIN. The silencer has a 1.5-inch diameter and is 6.4 inches long with no mount. The rear of the silencer is threaded 1.375-24tpi to accommodate HUB compatible mounting systems; the tested direct-thread mount increased the total system length to 6.8 inches. The silencer is 3D-printed titanium and weighs 8.5 ounces with no mount. The tested direct-thread mount weighs 2 ounces, resulting in a total tested system weight of 10.5 ounces. The Strake 9 can be obtained directly from LayerX Suppression.
Silencer Hazard Map:
The predicted personnel hazards generated by the tested weapon system in this report, in the free field, are shown in the adjacent Silencer Hazard Map. Click or tap the Map to enlarge. Please reference Silencer Hazard Map Brief 8.1.28 for further details. The PEW-SOFT HD Blast Hazard Prediction Tool and Hazard Mapper is presented in Report 8.1.1.
LayerX Strake 9 HK MP5 9mm Subsonic Free Field Hazard Map Produced by PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
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-LayerX-157-001-26. Therefore, data pertaining to the Strake 9 in this Sound Signature Review is published with the express written permission of LayerX Suppression.
This Sound Signature Review contains testing and analysis results using the LayerX Strake 9 direct-thread mounted on the semiautomatic Heckler and Koch SP5 subgun, chambered in 9x19mm NATO with a 8.9-inch barrel. Speer Lawman 147gr ammunition was used in the tests, in which its velocity was subsonic. The standard PEW Science HK SP5-A2 test host weapon system is described in Public Research Supplement 6.85.
Section 6.231.1 contains the LayerX Strake 9 test results and analysis.
Section 6.231.2 contains Suppression Rating comparisons of both configurations of the LayerX Strake 9, Otter Creek Labs Universe-36, Dead Air Wolfman, CAT MOB, PTR VENT 2, Otter Creek Labs Lithium, HUXWRX CA$H 9K, Resilient Suppressors RS9, and GSL Phoenix fired on the Heckler and Koch SP5-A2.
Section 6.231.3 contains the review summary and PEW Science laboratory staff technical opinions.
Summary: When paired with the 8.9-in barrel HK SP5-A2 with 80-deg locking piece and fired with Speer Lawman 147gr, the LayerX Strake 9 mounted with a direct-thread mount achieved a composite Suppression Rating™ of 48.5 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
6.231.1 LayerX Strake 9 Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the LayerX Strake 9 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. LayerX Strake 9 Sound Metric Summary
6.231.1.1 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 returned to battery with an empty chamber. The HK MP5 family of submachine guns does not possess a bolt-hold-open feature. 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 dataset and bolt-closing signatures. 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 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 testing; the 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 LayerX Strake 9 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 5-shot test are shown in Figure 2a. In Figure 2b, a shorter timescale is shown comparing the impulse of Shot 1, Shot 2, and Shot 3.
Fig 1a. LayerX Strake 9 subsonic 9x19mm HK SP5-A2 Semiautomatic Subgun Muzzle Sound Pressure Signature
Fig 1b. LayerX Strake 9 subsonic 9x19mm HK SP5-A2 Semiautomatic Subgun Sound Pressure Signature
Figure 2a. LayerX Strake 9 subsonic 9x19mm HK SP5-A2 Semiautomatic Subgun Muzzle Sound Impulse Signature
Figure 2b. LayerX Strake 9 9x19mm HK SP5-A2 Semiautomatic Subgun Muzzle Sound Impulse Signature
The LayerX Strake 9 is a multi-caliber hybrid design silencer that is intended to induce very low backpressure to reciprocating weapon systems. Hybrid designs incorporate both high flow rate features and conventional geometries to control distal blast propagation while reducing adverse influence on weapon function. For an overview of the three primary classes of rifle silencer designs in the PEW Science Silencer Sound Standard research taxonomy, the reader is encouraged to review PEW Science Research Supplement 6.169.
The internal design of the Strake 9 includes several features that increase surface area and turbulence, beginning in the first expansion (blast chamber) with protrusions and also present in ribs on each stepped-cone baffle. A spiral annulus is fed by venting in each baffle chamber and the structure terminates at the distal end in an eight-vent circumferential array. The early and late time flow rate of the Strake 9 is relatively high, as a result.
The blast overpressure and impulse signatures measured from the Strake 9 demonstrate the behavior of the above design features. The following observations are noted:
Blowdown is of very short duration, with relatively high amplitude (Fig. 1a).
Primary jetting is immediate and forms the highest amplitude pressure feature, in early time. Significant jetting follows (Fig. 1b).
Precursor momentum is relatively consistent (Fig. 1b and Fig. 2b) with first-round-pop (FRP) divergence occurring early but not severely. FRP is somewhat controlled but defined.
Post-FRP combustion propagation is relatively consistent, from shot to shot (Figure 2).
Observations (1) and (2) are consistent with the silencer’s design and its functional intent. Observation (3) is somewhat notable in that FRP from the Strake 9 is much more controlled than from the HUXWRX CASH 9K (6.97), another high flow rate silencer. The FRP is also more controlled than from the short configuration of the Dead Air Wolfman (6.182); a relatively high back pressure silencer. It should be noted that both the HUXWRX and short configuration of the Dead Air silencer are shorter than the Strake 9, which is disadvantageous for FRP control. Nonetheless, given the general size and weight of these compact silencer systems, these comparisons may prove valuable for end users.
PEW Science Research Note 1: Calculations from the test data indicate that the aforementioned FRP from the LayerX Strake 9 is less than 5 percent more severe to bystanders, on average, than are subsequent shots. Its flow rate does not appear to significantly influence this performance factor.
PEW Science Research Note 2: The muzzle signature from the Strake 9 is relatively similar in severity, on average, to the short configuration of the Dead Air Wolfman on the MP5 weapon system. This is a consequence of the higher flow rate from the Strake 9, despite its more advanced internal design. The Strake 9 outperforms the HUXWRX CASH 9K in every signature reduction metric. Some silencers with relatively high early-time flow rates begin to outperform the Strake 9, such as the Resilient Suppressors RS9 (6.90). Generally, the Strake 9 will be outperformed by silencers like the Otter Creek Labs Lithium (6.102) and larger Otter Creek Labs Universe-36 (6.223), though the back pressure from those silencers will be higher, depending on configuration. Users should note that operator (shooter’s ear) Suppression Ratings may be similar between silencers even with back pressure differences, depending upon muzzle blast coalescence, and the time regime in which back pressure manifests in different silencers. For example, although the Lithium has a shooter’s ear Suppression Rating on the MP5 that is very close to that of the Strake 9, the Strake 9 will likely have less “gas blow back” due to its gross flow rate.
PEW Science Research Note 3: Larger or more advanced silencers generally outperform more compact or primitive silencers in pure suppression performance on submachine guns. The GSL Phoenix (6.86), which is an update to the legacy Gemtech MK-9K, has higher suppression performance, but is larger. Advanced hybrid designs like the CAT MOB (6.148) and PTR VENT 2 (6.131) will provide even higher suppression performance, with combined back pressure reduction, at the expense of size.
Operator hazard comparisons are provided in Section 6.231.2 of this report.
PEW Science Research Note 4: As in most semiautomatic 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 85 ms in Figure 1a) the mechanical noise of the bolt closing is observed. The pressure signature of Shot 6 still displays this event due to the bolt not remaining open after the sixth and final round is fired from the magazine on the HK SP5-A2 weapon system. The bolt is closing on an empty chamber.
PEW Science Research Note 5: The closing time of the HK SP5-A2 bolt is directly related to the flow restriction of a silencer used with the weapon system. PEW Science has determined bolt closing time variation from the unsuppressed state may sometimes be used as an indicator of silencer back pressure, with strong correlation with the PEW Science Back Pressure Metric, Omega, with rifle cartridges, particularly on the MK18 weapon system. PEW Science Omega Metric and alpha parameter research in the subsonic 9x19mm combustion regime with the HK SP5-A2 and SP5K-PDW weapon systems is ongoing. Note that the PEW Science HK SP5-A2 possesses an 80-deg locking piece in its bolt carrier group, which may result in lower bolt carrier group rearward velocity than systems possessing standard angle locking pieces. This lower rearward velocity may result in delayed forward return velocity, when compared with other systems.
It is also important to note that PEW Science has determined bolt closing time to be an unreliable indicator upon upper receiver fouling in some weapon systems, such as the MK18 or M4A1. Sound signatures are typically not influenced by this fouling, as these kinematics occur in late time, after gas venting to atmosphere. Note that the roller-delayed blowback action of the HK SP5-A2 is significantly different than the direct gas impingement operated locked bolt action of the MK18. These factors, in addition to the difference in combustion regime amplitudes of supersonic 5.56x45mm and subsonic 9x19mm, result in a different influence of mechanical weapon noise to the total signature to which bystanders and the shooter are subjected.
As always, it is important to note that 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 semiautomatic firearm configuration.
PEW Science Research Note 6: Note that the muzzle Suppression Rating of the LayerX Strake 9 with the direct-thread mount is 47.5 and the shooter’s-ear Suppression Rating is 39.8; which are the different zones on the Suppression Rating Dose Chart. This demonstrates a typical performance attribute for silencers that are both high flow rate and compact when they are fielded on submachine guns. The gross suppression of a silencer, as well as its flow rate, influences the holistic signature on the standard HK SP5-A2 weapon system.
The signatures measured at the shooter’s ear are presented and analyzed in the full Member Version of this report.
The operator hazard level from some silencers with higher back pressure than the Strake 9 on this weapon system is similar, even though their muzzle suppression is higher. These systems are compared in the following section.
6.231.2 Suppression Rating Comparison (Subsonic 9x19mm from the HK SP5-A2)
Figure 9 presents a comparison of the PEW Science Suppression Rating of the LayerX Strake 9 with direct-thread mount to that of the OCL Universe-36, two configurations of the Dead Air Wolfman, CAT MOB, PTR VENT 2, OCL Lithium, HUXWRX CA$H 9K, Resilient Suppressors RS9, and GSL Phoenix on the HK SP5-A2 system. The standard PEW Science HK SP5-A2 test host weapon system is described in Public Research Supplement 6.85.
Figure 9. Suppression Rating Comparisons of the LayerX Strake 9, Otter Creek Labs Universe-36, Dead Air Wolfman with the CAT/MOB/A1, PTR VENT 2, Otter Creek Labs Lithium, HUXWRX CA$H 9K, Resilient Suppressors RS9, and GSL Phoenix on the HK SP5-A2, Using PEW-SOFT 9x19mm Subsonic Test Data and PEW Science Analysis
Figure 9 presents an overall summary of the postulated hazards to the operator and bystanders when fielding a LayerX Strake 9 on the HK MP5 weapon system. Data is also presented for the Otter Creek Labs Universe-36 (6.223), Dead Air Wolfman (6.182), GSL Phoenix (6.86), Otter Creek Labs Lithium (6.102), Resilient Suppressors RS9 (6.90), PTR VENT 2 (6.131), and the CAT MOB (6.148). 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. 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. Signature tone is inherently “baked-in” to the calculation.
The following gross conclusions can be made from the above with details from the other referenced studies:
The muzzle (bystander) Suppression Rating of the LayerX Strake 9 is similar to that of the short configuration of the Dead Air Wolfman and the HUXWRX Cash 9K. However, the back pressure generation of the Wolfman (regardless of its long or short configuration) is higher, and the FRP of the Cash 9K is more severe.
The relatively high flow rate of the Strake 9 enables it to achieve an average shooter’s ear (operator) Suppression Rating similar to that of the OCL Universe-36, Lithium, and approaching that of the GSL Phoenix. This occurs despite those silencers having higher gross muzzle suppression performance. This phenomenon is driven by flow rate and a lower degree of ejection port blast hazard from the MP5 as a result of that flow rate. Note that users will certainly perceive silencers like the GSL Phoenix as “quieter” overall, due to the total pressure field and late time effects. However, acute hazard to the operator, in the free field, is similar.
As previously discussed in Research Note 2, users should note that operator (shooter’s ear) Suppression Ratings may be similar between silencers even with back pressure differences, depending upon muzzle blast coalescence, and the time regime in which back pressure manifests in different silencers. For example, although the Lithium has a shooter’s ear Suppression Rating on the MP5 that is very close to that of the Strake 9, the Strake 9 will likely have less “gas blow back” due to its gross flow rate.
As detailed in this report, the Suppression Rating at the shooter’s ear may be significantly influenced by both the muzzle signature and the ejection port signature from reciprocating weapon system; all other things equal.
PEW Science Research Note 11: The signature to which the shooter’s ear is subjected is a function of both ejection port and muzzle signature. When the silencer’s endcap is in closer proximity to the shooter, the severity is increased. The coalescing of the ejection port blast overpressure with the primary muzzle blast may exacerbate the severity of the signature at the shooter’s head position. It is not ejection port signature, alone, that dictates the signature measured at the shooter’s head position. As noted in the full Member Version of this article, mechanical noise factors also play a role in shooter hazard.
As the published suppressed HK MP5/SP5 dataset continues to grow, two significant conclusions drawn in previous articles once again hold true in this data and analysis:
The roller-delayed blow back MP5 operating system is still a blow back system. The delay, even when maximized with the 80-deg locking piece, still does not completely eliminate gas sensitivity during suppressed use. Silencer back pressure still influences the signature at the shooter’s ear on this suppressed weapon system.
The Flow-Baffles in the HUXWRX CA$H 9K, early-time venting in the Resilient Suppressors RS9, PIP technology in the PTR VENT 2, and DiVerge technology in the CAT MOB all significantly reduce back pressure. The suppression performance of those four silencers to the shooter in the subsonic pistol cartridge regime is notable, and the MP5 is gas sensitive enough for their back pressure reduction to have efficacy. The early and continuous venting design of the LayerX Strake 9 evaluated in this report further illustrates the benefit of high flow rate designs, even on the pistol-caliber roller-delayed blow back system.
Further study of the suppressed roller-delayed blow back system is a subject of continued PEW Science research.
The user is encouraged to be mindful of the degree to which sound signature suppression, and resulting personnel hazards, can vary across designs. 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.
6.231.3 Review Summary: LayerX Strake 9 on the HK SP5 9x19mm Subgun with 8.9-in barrel
When paired with the 8.9-in barrel HK SP5-A2 with 80-deg locking piece and fired with Speer Lawman 147gr, the LayerX Strake 9 mounted with a direct-thread mount achieved a composite Suppression Rating™ of 48.5 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 LayerX Strake 9 is a compact, relatively lightweight submachine gun silencer that has lower back pressure than several conventional designs. Though it is 3D-printed titanium, the Strake 9 is robust enough for use on both 5.56 NATO and 7.62 NATO weapons, in addition to pistol cartridges, in accordance with the manufacturer's firing schedule. At only 6.5 inches long and 8.5 ounces without a mount, it is likely that the Strake 9 will find suitable use on personal defense weapons. Users should note that the back pressure of the Strake 9 is very low, and the gross signature suppression performance will be lower than some larger and more advanced submachine gun silencers. Nonetheless, ejection port blast hazards are significantly reduced with the Strake 9, and therefore acute operator hazards in the free field are on par with many competing models.
The internal design of the Strake 9 includes several features that increase surface area and turbulence, beginning in the first expansion (blast chamber) with protrusions and also present in ribs on each stepped-cone baffle. A spiral annulus is fed by venting in each baffle chamber, and the structure terminates at the distal end in an eight-vent circumferential array. The early and late time flow rate of the Strake 9 is relatively high as a result.
The muzzle signature from the Strake 9 is relatively similar in severity, on average, to the short configuration of the Dead Air Wolfman on the MP5 weapon system. This is a consequence of the higher flow rate from the Strake 9, despite its more advanced internal design. The Strake 9 outperforms the HUXWRX CA$H 9K in every signature reduction metric. Some silencers with relatively high early-time flow rates begin to outperform the Strake 9, such as the Resilient Suppressors RS9. Generally, the Strake 9 will be outperformed by silencers like the Otter Creek Labs Lithium and larger Otter Creek Labs Universe-36, though the back pressure from those silencers will be higher, depending on configuration. Users should note that operator (shooter’s ear) Suppression Ratings may be similar between silencers even with back pressure differences, depending upon muzzle blast coalescence, and the time regime in which back pressure manifests in different silencers. For example, although the Lithium has a shooter’s ear Suppression Rating on the MP5 that is very close to that of the Strake 9, the Strake 9 will likely have less “gas blow back” due to its gross flow rate.
Larger or more advanced silencers generally outperform more compact or primitive silencers in pure suppression performance on submachine guns. The GSL Phoenix, which is an update to the legacy Gemtech MK-9K, has higher suppression performance, but is larger. Advanced hybrid designs like the CAT MOB and PTR VENT 2 will provide even higher suppression performance, with combined back pressure reduction, at the expense of size.
With regard to system performance and user perception, the relatively high flow rate of the Strake 9 enables it to achieve an average shooter’s ear (operator) Suppression Rating similar to that of the OCL Universe-36, Lithium, and approaching that of the GSL Phoenix. This occurs despite those silencers having higher gross muzzle suppression performance. This phenomenon is driven by flow rate and a lower degree of ejection port blast hazard from the MP5 as a result of that flow rate. Note that users will certainly perceive silencers like the GSL Phoenix as “quieter” overall, due to the total pressure field and late time effects. However, acute hazard to the operator, in the free field, is similar.
The LayerX Strake 9 is 3D-printed titanium, and the manufacturer lists it as being compatible with full-power rifle cartridges like 5.56 NATO and .308 WIN. PEW Science has not evaluated the durability of the Strake 9. The user is encouraged to contact the manufacturer to ensure their desired use case is supported.
In addition to fixed-barrel weapons, it is possible that the Strake 9 may be used on semiautomatic handguns as it is HUB mounting system compatible. The use of a silencer on a modified tilting-barrel Browning action may be accomplished through the use of an inertial decoupler assembly. PEW Science has not evaluated the Strake 9 in such a configuration. In general, PEW Science recommends the user contact both the silencer manufacturer and weapon manufacturer prior to creating and operating a suppressed weapon system from these components.
In this review, the LayerX Strake 9 performance metrics depend upon suppressing a subsonic centerfire pistol cartridge on a roller-delayed blowback submachine gun. While the sound signature of such cartridges can be suppressed to levels that may result in the desire of the shooter and bystanders to not wear hearing protection, PEW Science encourages the reader to remain vigilant with regard to all subsonic pistol cartridge suppression claims. The gas volume and combustion products created by firing a subsonic centerfire pistol cartridge such as 9x19mm are still significant; the measured pressure and impulse magnitudes, and their durations, illustrate this fact. Silencer performance on automatic (reciprocating) weapons depends on many factors. Weapon configuration may significantly influence total suppressed small arm system performance.
The hearing damage potential of subsonic submachine gun use is not insignificant. PEW Science encourages the reader to consider the Suppression Rating when deciding on an appropriate silencer and host weapon combination for their desired use.
