SSS.6.134 - SilencerCo Velos LBP and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle (Free Version)
/SilencerCo Velos LBP on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The Velos LBP is designed and manufactured by SilencerCo. It is a 223 caliber centerfire rifle silencer, intended to suppress the 5.56x45mm cartridge, with no barrel length restrictions. It has a 1.73-inch diameter and the silencer is 6.2 inches long with the direct-thread Multiple Accessory Attachment Device (MAAD) mount installed. The silencer may also mount to the host firearm with other MAAD mounts or any other adapters possessing the SilencerCo Charlie rear thread pattern (1.375”-32tpi). The silencer core is constructed from 3D-printed Inconel 625 alloy, with forward and aft welded sections being 17-4 heat treated stainless steel. The Velos LPB weighs 18 ounces with the MAAD direct-thread mount, as tested. The Velos LBP can be obtained from Silencer Shop.
This Sound Signature Review contains single-test results using the Velos LBP mounted with the MAAD Direct-Thread mount on the MK18 Automatic AR15 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 6.134.1 contains the Velos LBP test results and analysis.
Section 6.134.2 contains Suppression Rating comparisons of the Velos LBP with dedicated 223 and 30 caliber silencers on the current market, including the 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 6.134.3 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 SilencerCo Velos LBP mounted with the MAAD Direct-Thread mount achieved a composite Suppression Rating™ of 31.9 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
6.134.1 SilencerCo Velos LBP Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the Velos LBP 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. SilencerCo Velos LBP Sound Metric Summary
6.134.1.1 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 Velos LBP 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, Shot 3, and Shot 5.
Fig 1a. SilencerCo Velos LBP 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. SilencerCo Velos LBP 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature
Figure 2a. SilencerCo Velos LBP 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. SilencerCo Velos LBP 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
The SilencerCo Velos LBP rifle silencer is a so-called hybrid design. For an overview of the three primary classes of rifle silencer designs, the reader is encouraged to review PEW Science Research Supplement 6.124.
As a hybrid design, the Velos LBP contains elements of both conventional and high flow rate designs, combined such that minimization of early-time internal blast impulse accumulation is realized, without regard to the degree to which external gas momentum accumulation occurs. The minimization of blast chamber impulse accumulation (alpha parameter) without regard to the minimization of the PEW Science Omega Metric research parameter (detailed in public Research Supplement 6.40), enables a silencer design to provide both favorable weapon kinematics and more favorable sound field even near reflecting surfaces. In the case of the Velos LBP however, its Omega Metric is still relatively low; this is a consequence of its direct distal venting. Direct distal venting through shorter path lengths has been shown to induce this phenomenon (see Research Note 2, below). This is one of the reasons for the lower muzzle Suppression Rating of the Velos LBP and potentially more severe signature outside of the free field, near reflecting surfaces. This research is ongoing.
PEW Science Research Note 1: The Omega Metric minimization (expedient rise to maximum positive phase impulse, Fig 2a) of the Velos LBP, and its lower impact on weapon kinematics (see Figure 3b, Member Review) is serendipitous. Because this gas momentum behavior is a direct consequence of distal venting, it may be assumed that favorable weapon kinematics, such as slower cyclic rate, always correlate directly with this externally measured parameter. On the contrary, it is a combination of both early time impulse accumulation in the blast chamber and later time externally measured impulse accumulation that define the gas dynamics of the silencer system. In addition to its distal venting, the Velos LBP also possesses internal venting of its blast baffle assembly, which allows blast load propagation to its annular spiral cavities. This internal vent array minimizes early time gas phase blast impulse accumulation near the muzzle orifice, which helps to nullify the additive impulse from the initial shock phase of the loading.
PEW Science Research Note 2: Similar design attributes to those noted above are observed in the following rifle silencers previously evaluated by PEW Science, albeit in varied configurations:
Rifle silencers with CGS Hyperion Technology (Hyperion, Hyperion K, and the Helios QD) - early-time venting to annular space with or without direct distal venting.
OSS and HUXWRX Helix HX-QD and FLOW series Flow-Through rifle silencers - direct early-time venting to annular space with toroidal overlapping gas paths and direct distal vent arrays.
Sig Sauer SLH series Forward Flux rifle silencers - direct annular porting and direct distal vent arrays.
Liberty Precision Machine Torch - direct early-time venting with or without direct distal venting.
CAT ODB and WB SURGE BYPASS rifle silencers - direct early-time venting to annular cavities with multiple stages and complex distal venting.
There are notable differences between the technologies in all of the above silencer designs, including in the design of the SilencerCo Velos LBP. With respect to the performance attributes of the Velos LBP, the following differences are noted:
The Velos LBP shares partial Hoplon blast baffle geometry with that of the SilencerCo Saker (6.53) with the addition of multiple porting arrays. In function, these arrays are more similar to those in the LPM Torch than other silencers, above. The Velos LBP also uses traditional baffle geometry through much of its core.
The annular cavities of the Velos LBP are similar to those in the Sig and CAT silencers; the Velos has less frequent annular venting than the Sig Forward Flux technology and less gas stages and considerably more simple distal venting than CAT SURGE BYPASS technology.
While the OSS/HUXWRX Flow-Through and CAT SURGE BYPASS technologies do share some similarities with the SilencerCo Velos LBP, the early-time expansion (blast) chamber vent array in the Velos LBP is less pronounced and in a different configuration than in both HUXWRX and CAT rifle silencers.
As a result of the above, the SilencerCo Velos LBP exhibits 5.56x45mm suppression behavior that is similar to Flow-Through and Surge Bypass but not as refined. The following note provides quantitative performance differentials.
PEW Science Research Note 3: There are direct, measurable performance factors exhibited by the SilencerCo Velos LBP that differentiate its behavior from the aforementioned silencers:
From its distal vent array fed from the annular cavities, significant early time pressure in the positive phase is noted, similar to that observed with the HUXWRX FLOW 762 Ti (6.114) and other HUXWRX silencers (Figure 1b). Furthermore, erratic external impulse accumulation is noted later in the shot string, after Shot 3 (see Figure 2b). Like in HUXWRX Flow-Through technology, the SilencerCo LBP technology appears to be heavily temperature sensitive.
The first-round-pop (FRP) signature differential from the Velos LBP is severe. And, in accordance with the temperature sensitive performance noted above, Shot 5 in the string reaches FRP levels of external gas momentum, as shown in the aforementioned figure. With the Velos LBP on this short 10.3-in barrel platform, FRP signature is characterized not only by more severe gas momentum accumulation, but clear delineation of secondary combustion propagation (ref. Fig 2b, 30.6 ms). It is important to note that in the absence of lengthened annular flow paths, direct distal venting often results in this type of severe gas propagation. Whereas the HUXWRX silencers use overlapping geometry to maximize the duration of gas travel through the annular paths, and the CAT ODB (6.120) and CAT WB (6.129) silencers use complex distal vent arrays in the SURGE BYPASS system to nullify this propagation after staged reduction, the Velos LBP appears to simply combine direct annular venting with its traditional baffle geometry. The reader is encouraged to study the differences in gas momentum consistency between these three types of silencers. The consistency of the Velos LBP signature throughout the shot string is much closer to that of the HUXWRX silencers than that of the CAT designs.
Despite the above performance compromise, the SilencerCo Velos LBP does induce less bolt carrier group speed increase than typical rifle silencer designs. Furthermore, the traditional baffle components in its hybrid design may result in more favorable sound signature suppression performance in certain combustion regimes, than some competing designs. More research is needed.
In summary, the SilencerCo Velos LBP provides an overall signature on the standard MK18 weapon system that is similar in consistency to HUXWRX Flow-Through FLOW rifle silencer systems, but with more severe FRP, and induces similar weapon kinematics as CAT SURGE BYPASS rifle silencer systems, with lower suppression performance to bystanders. While it is possible the near field sound field characteristics near reflecting surfaces with the Velos LBP may be favorable when compared to legacy HX-QD Helix systems, more research in this area is needed. As it stands, free field blast propagation analysis indicates that the overall Suppression Rating parameters of the Velos LBP on the MK18 are nominally less severe than that of the legacy HUXWRX (OSS) HX-QD 556 (6.54). This performance differential may increase outside of the free field.
PEW Science Research Note 4: 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 85 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 5: The closing time of the MK18 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. There are other signature features measured at the shooter’s ear which may further assist with quantifying weapon kinematics.
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 6: Note that the muzzle Suppression Rating of the SilencerCo Velos LBP is 28.7 and the at-ear Suppression Rating is 28.1; the same zone on the Suppression Rating Dose Chart. Unlike many rifle silencers, the high early time flow rate of the Velos LBP is beneficial to the sound signature at the shooter’s ear on the standard MK18 weapon system. The resulting back pressure of the Velos LBP is low, and the muzzle signature is suppressed adequately enough, that the weapon operator is subjected to less significant hearing damage risk.
6.134.2 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 6 presents a comparison of the PEW Science Suppression Rating of the SilencerCo Velos LBP to that of other rifle silences on the MK18 automatic AR15 rifle. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Figure 6. Suppression Rating Comparisons of the SilencerCo Velos LBP and other silencers, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis
Figure 6 presents detailed PEW Science Suppression Ratings, computed at the muzzle and ear, for the listed silencers. The Suppression Rating is a holistic parameter that captures human inner ear damage risk potential from a measured impulsive 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.
It is very important to note that performance differentials outside the free field (e.g. near reflecting surfaces) may not scale linearly across all designs. This is due to blast load reflection factors varying with both amplitude and wave shape, along with other waveform components.
From the above data, it can be concluded that the SilencerCo Velos LBP exhibits extremely competitive performance on the standard untuned MK18 weapon system as a dedicated 5.56mm silencer, with regard to overall hazard reduction and especially hazard reduction to the weapon system operator:
When compared to the legacy SilencerCo Saker 556 (6.53), the design changes introduced in the Velos LBP enable it to provide a significantly higher shooter’s ear Suppression Rating with a marginal drop in bystander protection.
The Suppression Rating at the Shooter’s Ear of the Velos LBP is only bested by CAT and HUXWRX models; rifle silencers using considerably advanced technology. For the SilencerCo system to accomplish this gross suppression performance at the operator’s position with its relatively simple design, is notable.
As discussed in the preceding section, free field blast propagation analysis indicates that the overall Suppression Rating parameters of the Velos LBP on the MK18 are nominally less severe than that of the legacy HUXWRX (OSS) HX-QD 556 (6.54). This performance differential may increase outside of the free field. More research is needed to quantify performance differentials of suppressed weapon systems in varying operating environments.
High flow rate hybrid design silencers like the SilencerCo Velos LBP may provide considerably lower hazard to the weapon operator on untuned weapon systems like the standard MK18, when compared to traditional restrictive rifle silencer designs such as the Otter Creek Labs Polonium (6.75) and YHM Turbo (6.98). When compared with significantly over-bored traditional designs like the Energetic Armament ARX (6.82) or Rugged Razor762 (6.85), hybrid designs like the Velos LBP may provide higher gross hazard reduction in most if not all environments.
PEW Science Research Note 9: Due to the breadth of the Silencer Sound Standard testing and analysis pedigree, the reader is encouraged to examine the spectrum over which suppression performance on the MK18 has been demonstrated. There exist silencers evaluated on the 5.56x45mm short barrel rifle platform that have significantly lower performance. Because the PEW Science Suppression Rating is a damage risk criterion (DRC), a lower Suppression Rating indicates a higher personnel hazard in the free field. Therefore, silencers such as the Thunder Beast Dominus (6.105), the Dead Air Sandman-S (6.92), and WARCOMP-equipped Surefire silencers, are postulated to be more hazardous to the unprotected ear than silencers like the SilencerCo Velos LBP. To iterate, the Suppression Rating is a DRC - it is not a subjective quantity; it is an objective quantification of hearing damage risk potential.
As shown in Figure 6, the Suppression Rating at the shooter’s ear may be significantly influenced by the ejection port signature from the MK18; 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.
Further laboratory testing of the SilencerCo Velos LBP on the standard PEW Science 14.5-in M4A1 test host weapon system is forthcoming.
6.134.3 Review Summary: SilencerCo Velos LBP 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 SilencerCo Velos LBP mounted with the MAAD Direct-Thread mount achieved a composite Suppression Rating™ of 31.9 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 SilencerCo Velos LBP is a full size 5.56mm machine gun rated rifle silencer that exhibits significant back pressure reduction and blast load hazard reduction for the weapon system operator on standard automatic rifles. The silencer is of hybrid design, utilizing both traditional silencer baffle elements and vent arrays to manage gas flow. For the SilencerCo system to accomplish high gross suppression performance at the operator’s position with its relatively simple design, is notable. The silencer is partially 3D-printed from Inconel alloy and is reported to exhibit significant durability.
When compared to the legacy SilencerCo Saker 556, the design changes introduced in the Velos LBP enable it to provide a significantly higher shooter’s ear Suppression Rating with a marginal drop in bystander protection. The Suppression Rating at the Shooter’s Ear of the Velos LBP is only bested by CAT and HUXWRX models; rifle silencers using considerably advanced technology.
As discussed in this white paper, free field blast propagation analysis indicates that the overall Suppression Rating parameters of the Velos LBP on the MK18 are nominally less severe than that of the legacy HUXWRX (OSS) HX-QD 556. This performance differential may increase outside of the free field. More research is needed to quantify performance differentials of suppressed weapon systems in varying operating environments.
High flow rate hybrid design silencers like the SilencerCo Velos LBP may provide considerably lower hazard to the weapon operator on untuned weapon systems like the standard MK18, when compared to traditional restrictive rifle silencer designs such as the Otter Creek Labs Polonium and YHM Turbo. When compared with significantly over-bored traditional designs like the Energetic Armament ARX or Rugged Razor762, hybrid designs like the Velos LBP may provide higher gross hazard reduction in most if not all environments.
The design of the Velos LBP does share some similarities with that of the legacy Saker 556, including the modular MAAD mounting system, which is relatively straightforward to use. It also shares partial Hoplon blast baffle geometry, with the addition of multiple porting arrays. The Velos LBP also uses traditional baffle geometry through much of its core. The annular cavities of the Velos LBP are similar to those in the Sig and CAT silencers; the Velos has less frequent annular venting than the Sig Forward Flux technology and less gas stages and considerably more simple distal venting than CAT SURGE BYPASS technology. While the OSS/HUXWRX Flow-Through and CAT SURGE BYPASS technologies do share some similarities with the SilencerCo Velos LBP, the early-time expansion (blast) chamber vent array in the Velos LBP is less pronounced and in a different configuration than in both HUXWRX and CAT rifle silencers. As a result, the SilencerCo Velos LBP exhibits 5.56x45mm suppression behavior that is similar to Flow-Through and Surge Bypass but not as refined.
It is likely, given the blast baffle shape, construction, and venting geometry of the Velos LBP, that the silencer is relatively durable on automatic weapons. No barrel length or firing schedule restrictions are stipulated. Nonetheless, the reader is encouraged to contact the manufacturer for guidance in accordance with their desired use case.
In this review, the SilencerCo Velos LBP 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.
