SSS.6.41 - OSS HX-QD 762 and the Savage Model 10 PC .308
/OSS HX-QD 762 on a Savage Model 10 .308 with 20-in Barrel
The HX-QD 762 is designed and manufactured by OSS. It is a 30 caliber centerfire rifle silencer, intended to suppress most cartridges with projectiles appropriately sized to travel through the bore, including 300 Winchester Magnum. It has a 1.62-inch diameter and is 7.1 inches in length. The silencer mounts to proprietary OSS LH-threaded taper-mount muzzle devices. The outer tube of the silencer is constructed of heat-treated 17-4 stainless steel, with the internal components being constructed of both 17-4 stainless steel and Grade 5 titanium. The silencer weighs 22.9 ounces with the Flash Hider-QD 762 taper mount, as tested. The HX-QD 762 can be obtained from Silencer Shop.
The HX-QD 762 Ti is also available, which reduces the system weight by 4.8 ounces while exhibiting similar sound suppression performance.
This review contains single-test results using the HX-QD 762 mounted with the Flash Hider-QD taper mount on the Savage Model 10 Precision Carbine rifle, chambered in .308WIN with a 20-inch barrel. Federal XM80C 149gr ammunition was used in the test.
- Section 6.41.1 contains the HX-QD 762 test results and analysis.
- Section 6.41.2 contains back pressure and Suppression Rating comparisons with selected compact to mid-size .30 rifle silencers possessing a PEW Science Back Pressure Metric, Ω [Pa-1] in Omega Zone 5 and below. Further information about the Ω metric and Omega Zones can be obtained in PEW Science Research Supplement 6.40 (Public Article).
- Section 6.41.3 contains a visual sound signature comparison of several "low back pressure" silencers in impulse [Pa-ms] space.
- Section 6.41.4 contains the review summary and PEW Science opinions.
Summary: When paired with the Savage M10 20” .308 and fired with Federal XM80C, the OSS HX-QD 762 mounted with the Flash Hider-QD 762 taper mount achieved a Suppression Rating™ of 35.1 in PEW Science testing.
Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings
6.41.1 OSS HX-QD 762 Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the HX-QD 762 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. OSS HX-QD 762 Sound Metric Summary
6.41.1.1 SOUND SIGNATURES AT THE MUZZLE
Real sound pressure histories acquired with PEW-SOFT™ are shown below. 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.
Figure 1 shows a 1 millisecond long portion of the first round sound pressure signature of the HX-QD 762 as measured 1.0 m left of the muzzle. There are four significant waveform features labeled:
The maximum amplitude of sound signature from internal weapon system combustion is measured to be 124.5 dB.
The endcap exit event results in an initial overpressure peak magnitude of 148.7 dB.
Peak FRP is reached at a maximum of 151.7 dB.
There is an unusually long duration of initial positive phase overpressure, denoted by the definitive return to negative phase over 0.4 ms after initial jetting.
This is an unusual sequence observed when firing supersonic .308WIN ammunition from a bolt-action rifle with an attached silencer that exhibits low flow restriction (back pressure); internal silencer design can significantly influence the measured timing and pressure amplitudes. Preliminary back pressure comparisons are shown in Section 6.41.2 of this review, with the PEW Science Back Pressure Metric, Ω [Pa-1].
Fig 1. OSS HX-QD 762 First Round Bolt Action Rifle Muzzle Sound Pressure Signature, 20-MAR-2021
Again, the waveform shown in Figure 1 is highly atypical. Unique features include not only an initial endcap exit and combined jet event with relatively high amplitude, but continuous positive phase amplitude for over 0.4 ms of duration; longer than any other centerfire rifle silencer has exhibited in supersonic .308 testing by PEW Science, to date. This phenomenon has not been observed in other low back pressure silencers tested by PEW Science. The Dead Air Sandman-K (Review 6.15), Rugged Radiant in the short configuration (Review 6.12), and even the CGS Helios QD with Vented Endcap (Review 6.13) do not experience this initial long duration positive pressure phase, though the vented Helios QD does come close.
Closer views of the first peak of all shots (Fig 2a) and highest peak of the first shot (Fig 2b) are shown below. Figure 2a illustrates the consistency of the internal weapon system and silencer combustion events between all 5 shots during the test, followed by a consistent endcap exit event with immediately apparent influence of internal silencer atmosphere (noted in FRP and to a lesser extent in Shot 5). It is somewhat atypical for later shots to exhibit higher early-time pressure amplitude during projectile exit and jetting; another anomalous characteristic of the OSS HX-QD 762 sound signature. Prior to this measured anomaly, the early time combustion event consistency in both amplitude and wave shape from the high sample rate and raw, unfiltered data stream from PEW-SOFT is significant. Figure 2b shows points later in time during Shot 1 as the maximum sound pressure occurs from the primary combustion event. Note that the total timescale in Figure 2a is 0.28 milliseconds (280 microseconds) and the total timescale in Figure 2b is only 0.1 milliseconds (100 microseconds). PEW-SOFT provides a sampling point every microsecond and the individual data points are shown in Figure 2b to illustrate this.
Fig 2a. OSS HX-QD 762 Bolt Action Rifle Muzzle Sound Pressure Early-Time Peaks, 20-MAR-2021
Fig 2b.OSS HX-QD 762 Bolt Action Rifle Muzzle Sound Pressure Shot 1 Peak, 20-MAR-2021
The primary sound signature pressure histories for all 5 shots with the HX-QD 762 are shown in Figure 3a. The sound signatures of Shot 1, Shot 2, and Shot 3 are shown in Figure 3b, in early time. The real sound impulse (momentum transfer potential) histories from the same 5-shot test are shown in Figure 4a. In Figure 4b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shot 2 and Shot 3.
Fig 3a. OSS HX-QD 762 Bolt Action Rifle Muzzle Sound Pressure Signature, 20-MAR-2021
Fig 3b. OSS HX-QD 762 Bolt Action Rifle Muzzle Sound Pressure Signature, Short Time Window, 20-MAR-2021
Figure 4a. OSS HX-QD 762 Bolt Action Rifle Muzzle Sound Impulse Signature, 20-MAR-2021
Figure 4b. OSS HX-QD 762 Bolt Action Rifle Muzzle Sound Impulse Signature, Short Time Window, 20-MAR-2021
The HX-QD 762 does not exhibit significantly perceptible first round pop (FRP) at the muzzle on this platform; this is typical for silencers with high flow rate, which is discussed below. Nonetheless, the FRP phenomenon is observable in the pressure regime, and it is further evident upon examination of the impulse waveforms in Figure 4 in both impulse rise time and slope. PEW Science inner ear modeling indicates FRP will be more perceptible to bystanders than to the shooter with the HX-QD 762 on this host weapon platform.
PEW Science Note 1: The OSS HX-QD 762 exhibits a highly atypical muzzle sound signature in impulse space. The rise time to peak is relatively fast, but so is the decay from peak. In addition to this fast rise of impulse accumulation and fast decay rate, the lack of significant oscillatory events in the overpressure history are apparent in the impulse waveforms; that is, the impulse waveforms are smooth. This consistent data trend in impulse space during decay, post-peak, is highly atypical and is postulated to result from consistent flow rate increase and decrease exhibited by the silencer. PEW Science postulates that the flow rate of the HX-QD 762 maintains consistency through a wider gas velocity regime than typical silencer designs.
PEW Science Note 2: Comparisons with other low backpressure compact silencers in impulse space are shown in Section 6.41.3 of this review. There are significant differences in sound signature between the HX-QD 762 and other silencers exhibiting low flow restriction in the supersonic flow regime; namely, peak impulse amplitude and rise/decay.
The overall, muzzle, and ear Suppression Ratings for silencers tested by PEW Science, to date, can be compared directly using the tool in Section 7 of the Silencer Sound Standard - PEW Science Rankings and Section 6.41.2 of this review presents a comparison of Suppression Rating and back pressure for silencers of similar flow rate. Comprehensive silencer back pressure comparisons for .30 rifle silencers are available in PEW Science Public Research Supplement 6.40.
The HX-QD 762 is quieter than the Dead Air Sandman-S (Review 6.11) at both the muzzle and ear on this weapon platform, while exhibiting lower back pressure (a lower Omega zone).
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 has made a concerted effort to characterize the FRP phenomenon with true physiological human inner-ear response analyses. Additional PEW Science Member Research Supplements containing this information will be published in the future.
6.41.1.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 5-shot test of the HX-QD 762 suppressor 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 5 shots are shown in Figure 5. The primary sound signature history is shown on the left. A zoomed-in timescale is displayed on the right, in the region of peak sound pressure for Shot 1, Shot 2, and Shot 3. The real sound impulse (momentum transfer potential) histories at the ear from the same 5-shot test are shown in Figure 6. Again, full and short timescales are shown.
Figure 5a. OSS HX-QD 762 Bolt Action Rifle Ear Sound Pressure Signature, 20-MAR-2021
Figure 5b. OSS HX-QD 762 Bolt Action Rifle Ear Sound Pressure Signature, Short Time Window, 20-MAR-2021
Figure 6a. OSS HX-QD 762 Bolt Action Rifle Ear Sound Impulse Signature, 20-MAR-2021
Figure 6b. OSS HX-QD 762 Bolt Action Rifle Ear Sound Impulse Signature, Short Time Window, 20-MAR-2021
When examining the impulse waveforms measured at the shooter’s ear with the HX-QD 762 (Figure 6), it exhibits less significant FRP in both the pressure and impulse regimes then at the muzzle. In PEW Science inner-ear modeling, there is no significant FRP noticeable to the shooter with the OSS HX-QD 762 on this platform. Despite the relatively high peak pressure and impulse measured at the shooter’s head position, the inner-ear response of the shooter is less pronounced than with silencers exhibiting similar pressure amplitudes, and significantly less pronounced than silencers exhibiting similar low flow restriction. PEW Science postulates this is due to gas velocity, flow rate, and flow consistency, which is apparent in the minimal presence of oscillatory events in the overpressure signature and corresponding smooth impulse waveforms.
The sound signature of the OSS HX-QD 762 and its influence on the human ear merit further study by PEW Science. The influence of waveform oscillations negatively influencing sound signature (especially large swings in impulse space) was noted to be significant in the analysis of the Griffin Armament Explorr EX3 at-ear waveforms in Review 6.36. The OSS silencer design may take advantage of a reduction in such phenomena. More research and testing is needed.
6.41.2 Relative Suppression Rating and Back Pressure Comparisons (.30 Rifle Silencers)
The OSS HX-QD 762 suppressor is intended to produce little to no flow restriction (back pressure) and still moderately suppress small arm weapon system sound signature to both the shooter and bystanders. PEW Science has developed an empirical relation to quantify the back pressure (flow restriction) of silencers. Figure 7 shows supersonic suppression and back pressure comparisons between selected 7.62mm (30 caliber) rifle silencers shown in public PEW Science Sound Signature Reviews, as of the date of this review publication. The results shown in Figure 7 are calculated from real test data acquired with PEW-SOFT. Please note the following:
- The PEW Science Back Pressure Metric, Ω [Pa-1], may be generated for any silencer and suppressed weapon system using any suitable raw external overpressure signature data acquired 1.0 m left of the silencer endcap. PEW Science highly recommends data acquisition in accordance with The Silencer Sound Standard.
- Omega Zones are presented in Table 2, below, which are intended to provide guidance to weapons developers, silencer designers, and end-users, with regard to flow restriction characteristics of different silencer designs. It is very important to note that silencers possessing a relatively high Ω can still provide functional use on weapon systems. Some weapon systems are more sensitive to Ω than others.
- It is important to note that a silencer’s Omega Zone can shift when using a mounting scheme that differs from that used in the testing referenced in the published PEW Science Sound Signature Reviews. This phenomenon occurs due to some silencer mounting schemes significantly influencing flow restriction with some silencer designs.
- The theoretical lower limit of flow restriction, or so-called "zero back pressure" would be represented by the unsupressed state, Ω = 0 [Pa-1].
- PEW Science acknowledges that other dynamic events occur within a suppressed weapon system that can also influence weapon function. Therefore, PEW Science acknowledges that Ω is not the sole parameter one must consider for total supppressed weapon system operation. However, PEW Science postulates that the Ω metric influence can be significant.
Figure 7. Omega Back Pressure Metric And Suppression Rating Comparisons Of .308 Rifle Silencers Using PEW-SOFT Data and Analysis
Omega characterizes silencer back pressure. It is important to note that back pressure is not blow back. The back pressure of a silencer is the flow restriction it introduces to a suppressed weapon system. The blow back phenomenon that can occur during the use of a suppressed weapon system is caused by the reciprocating system actuating too early relative to overpressure decay within the weapon system, resulting in exposure of excessive internal system overpressure to atmosphere. Some weapons may be tuned to function well with silencers in a high Omega Zone. Some weapons may require low-Omega silencers due to constraints in their operating system(s). Omega metric technical details can be found in PEW Science Public Research Supplement 6.40.
Table 2. PEW Science Back Pressure Metric Omega Zones And Suppressed Weapon System Functional Descriptions
In Section 6.41.1.1, it was noted that the HX-QD 762 exhibits significantly longer positive phase pressure duration, 1.0 m left of the silencer endcap, than any other 30 caliber silencer tested by PEW Science, to date. Ordinarily, one may surmise that such a positive phase duration would result in significantly low sound suppression performance. In the case of the OSS HX-QD 762, this is not the case. PEW Science postulates that the phenomenon may contribute to not only its low Omega Zone (back pressure) but its sound signature suppression performance balance with that low flow restriction.
The HX-QD 762 represents one of the most significant performance outliers in PEW Science testing, to date, as shown in Figure 7, above. The silencer exhibits significantly low back pressure (approaching that of the Dead Air Sandman-K) but with significantly higher sound suppression performance than the Sandman-K. Three silencers in Figure 7 exhibit similar “balanced” performance traits to the OSS HX-QD 762:
The HX-QD 762, Hyperion K, Sandman-S, and SOCOM762-RC2 each posses radically different silencer designs with similar performance balance of low back pressure with moderate sound suppression. The Hyperion K silencer achieves this balance through immediate venting to an outer annulus and generous bore. The Sandman-S addresses the issue with a generous bore and conventional baffle type. The SOCOM762-RC2 tackles the problem with aggressive venting. The HX-QD 762 uses helical ported elements to maintain flow, which is a key differentiator from the other silencers. Regardless of method, all four silencers are able to significantly reduce flow restriction (back pressure) and still keep their overall Suppression Rating above 30 on this host weapon platform. For this reason, PEW Science notes these silencers as significant performance outliers in the current 30 caliber silencer market.
The OSS HX-QD 762 uses a relatively complex internal geometry to maintain flow rate during operation. In addition to being included in the above group of four so-called balanced silencers, it is the current leader with regard to back pressure and sound signature suppression balance. The silencer is on the cusp of Omega Zone 1. For a silencer to exhibit such low back pressure; a level at which semiautomatic and automatic host weapon operation may not influenced by the silencer, and achieve a Suppression Rating in the mid-30s on this host weapon system, is unprecedented in PEW Science testing. It is very important to note that data in the supersonic flow regime should not be extrapolated to the subsonic flow regime.
6.41.3 Detailed Supersonic Waveform Comparisons of Low Back Pressure Silencers
It is prudent to discuss, and highlight visually, the sound signature components indicative of silencers exhibiting low flow restriction (low back pressure) in the supersonic flow regime. Figure 8a shows seven waveforms in impulse space; each of Shot 2 from a 5-shot test of each silencer. Shot 2 is presented, rather than Shot 1, to compare impulse rise-time and initial slope (the rate of rise) of the silencers without the influence of ancillary FRP combustion:
The Dead Air Sandman-K is significantly loud, but extremely fast to vent combustions gasses. It is the lowest back pressure silencer.
The YHM Resonator K delays venting and has the highest back pressure of this “low back pressure” group.
The OSS HX-QD 762 exhibits an extremely fast rate of rise to peak impulse, but is able to keep the amplitude relative low. Furthermore, the decay occurs faster than the other silencers, all while having minimal waveform oscillation, as previously discussed in this review.
The vented CGS Helios QD mirrors the impulse accumulation of the OSS HX-QD 762 in early time, but is unable to control the gas flow and this chaotic venting is postulated to be one of the reasons why it loses sound suppression performance compared to the HX-QD 762.
The short configuration of the Rugged Radiant also vents gas very quickly, but is also very loud.
The CGS Hyperion K suppresses relatively well, but does sacrifice some back pressure reduction to do so.
The Griffin Explorr EX3 exhibits very low flow restriction, but violent early time jetting prevents its Suppression Rating from reaching that of many higher performing silencers.
Figure 8a. Bolt Action Rifle Supersonic .308 Muzzle Sound Impulse Signature Comparison (Shot 2)
Peak sound pressure [dB], peak sound impulse [dB-ms], and Omega (Ω) [Pa-1], alone, do not determine the sound supression performance of a silencer. It is the combination of these and other waveform parameters that form the total sound signature and the influence on human inner ear response.
6.41.4 Review Summary: OSS HX-QD 762 on a Savage Model 10 .308 with 20-in Barrel
When paired with the Savage M10 20” .308 and fired with Federal XM80C, the OSS HX-QD 762 mounted with the mounted with the Flash Hider-QD taper mount achieved a Suppression Rating™ of 35.1 in PEW Science testing.
PEW Science Subjective Opinion:
The OSS HX-QD 762 is a mid-size, relatively heavy, and durable .30 rifle silencer that exhibits class-leading back pressure reduction with a notable balance of sound signature suppression performance in the supersonic flow regime. The HX-QD 762 is also offered in a titanium version which reduces the weight of the system by almost 5 ounces. Users should note that most silencers exhibit significantly different sound suppression characteristics in different flow velocity regimes, i.e. when suppressing supersonic vs. subsonic cartridges. This sound suppression performance variation, across different flow regimes, is more pronounced with silencers possessing high flow rate (low back pressure) characteristics, like the HX-QD 762.
The HX-QD 762 contains 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 aforementioned method by which the HX-QD 762 shapes gas flow and allows it to exit the silencer is significantly different than many silencers on the current market. As shown in this review, the flow characteristics of the silencer are observable in the measured data; the continuity of the impulse waveforms indicates flow consistency that would otherwise only be seen with flow associated with unsuppressed sound signatures. The significant reduction in peak sound signature overpressure and impulse amplitudes, with simultaneous high flow rate and flow consistency, is highly atypical. PEW Science is of the opinion that the presented test data and analysis validates the efficacy of specific attributes of the so-called OSS “Flow-Through” technology; namely the reduction in back pressure combined with moderate sound suppression. To date, the OSS HX-QD 762 represents the best balance of Suppression Rating and back pressure reduction in the supersonic flow regime measured by PEW Science.
The left-hand (LH) threaded taper mounts from OSS are simple to operate. They may be installed on the weapon system with an adjustable wrench; the mount bodies, themselves, serve as wrench-flats. The mount sits flush with the rear of the silencer when fully installed; there is no mount protrusion. 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 silencer is also offered in a titanium version, as stated above. The Ti version may be attractive to some users due to the weight reduction; PEW Science has tested the Ti version and noted similar Suppression Rating performance to the steel version tested. Detailed signature comparisons between the steel and Ti versions of this silencer are the subject of future PEW Science research. Durability of the steel silencer is expected to be higher than that of the Ti silencer. PEW Science has not evaluated the durability of the HX-QD 762 silencer system(s) on semiautomatic or automatic host weapons. Note that the nature of low flow restriction (low back pressure) silencers may influence durability. These phenomena are subjects of further research.
In this review, the HX-QD 762 performance metrics depend upon suppressing a supersonic centerfire rifle cartridge; no easy 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 .308WIN cartridge are significant; the measured pressure and impulse magnitudes, and their durations, illustrate this fact.
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.
