SSS.6.124 - Research Supplement: Subsonic 300 BLK Suppression Performance - Flow-Through vs. Forward Flux vs. SURGE BYPASS vs. Conventional Silencers. Head-to-Head Comparisons (Article Preview)

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HUXWRX HX-QD 762 vs. Sig Sauer SLH300Ti vs. Combat Application Technologies CAT/ODB/A1/718 vs. Surefire SOCOM300-SPS vs. Sig Sauer SRD762QD-Ti on a 300 BLK Bolt Action Rifle with 8-inch Barrel

There are a variety of technologies implemented in modern rifle silencers. Principally, silencers reduce the severity of the signature produced by a small arm weapon system by modifying the propagation of combustion gasses such that they enter the ambient atmosphere at a lower temperature and pressure than they would otherwise, had a silencer not been installed on the weapon. These parametric differentials, along with the rate of gas propagation, dictate the resulting suppressed small arm signature.

Currently, there exist three different primary classes of rifle silencer technology:

  1. Conventional designs, in which shock and blast loads are significantly reflected in early time, rearward toward the muzzle orifice, with later time gas propagation significantly restricted to atmosphere. Examples of such silencers include the Q Full Nelson (6.99), Surefire SOCOM300-SPS (6.57) and the Otter Creek Labs Hydrogen (6.94).  These silencers use technologies such as legacy straight cone designs, elements of Surefire Total Signature Reduction®, and others.

  2. High Flow Rate designs, in which blast reflections in the proximal expansion chamber are redirected, reduced, or otherwise altered to reduce the influence on reciprocating weapon function, with later time gas propagation expediently venting to atmosphere. Examples of these silencers include the HUXWRX OSS HX-QD 762 (6.45) and the Sig Sauer SLH300Ti (6.107) which use HUXWRX Flow-Through® and Sig Sauer Forward Flux technologies, respectively.

  3. Hybrid designs, in which elements of both Conventional and High Flow Rate silencers are used, coupled with other technology variations and staged elements to provide parametrically varied performance attributes. Such attributes include the ability to reduce early time shock reflections while significantly altering the rate of proximal venting. These silencers may allow for minimal reciprocating weapon functional influence, while at the same time significantly suppressing signature to the operator and bystanders. Hybrid designs span a large range of the market in both brand and performance in different combustion regimes.  These silencers include the CGS Hyperion (6.71), CGS Hyperion K (6.50), the Surefire RC2 family, and others.  Technologies implemented in these types of silencers are varied, including CGS Hyperion Technology, elements of Surefire Total Signature Reduction®, CAT SURGE BYPASS©, and others.

The above three classes of silencers produce varied performance on different weapon systems and with different ammunition types. Of the three classes, the most significant overall performance potentials remain confined to Hybrid designs, in accordance with the PEW Science Silencer Sound Standard public research pedigree, to date. There exists a subcategory of this class of silencers, that is shown to demonstrate efficacy in multiple flow regimes. To date, the best example of such a subcategory includes silencers like the Combat Application Technologies CAT/ODB/A1/718 (6.22). These silencers not only combine performance parameters from all three classes, but have been shown to demonstrate so-called pressure agnostic behavior, in which input variation exemplified by both supersonic and subsonic cartridge combustion regimes both result in high signature suppression efficacy.

It is important to note that many silencers exhibit significantly different performance when using supersonic and subsonic ammunition.  PEW Science Research Supplement 6.115 presented a performance comparison of HUXWRX Flow-Through technology with that of Conventional designs, in the supersonic ammunition combustion regime.  The performances of the Dead Air Nomad-Ti, Q Thunder Chicken, and HUXWRX FLOW 762 Ti were compared in that article, in significant detail.

This Research Supplement compares a different group of silencers, in the subsonic ammunition combustion regime.  In general, increasing gross flow rate through a silencer can significantly reduce signature suppression performance, particularly with subsonic ammunition.  However, certain designs may significantly outperform others in this regard.  Quantifying these performance differentials is essential for characterizing hazards to the system operator and bystanders.

6.124.1 Quantifying Sound Suppression Performance

The severity of a suppressed small arm weapon signature, to the human inner ear, is quantified by the PEW Science Suppression Rating (Figure 1). As the Suppression Rating is a Damage Risk Criterion (DRC), it only expresses the degree to which a human may experience hearing damage. Although complex signature characteristics are included in its computation, the end result is only a DRC. Suppression Rating Rankings can be found in Section 7 of the Standard.

The nature of human inner ear response, and human interpretation of such response, dictates further signature examination if one desires information outside the purposes of DRC use. For example, end users may be interested in “how a silencer sounds,” rather than in the hearing damage risk potential of using the silencer on their weapon. The two phenomena are not necessarily coupled for all users.

The Suppression Rating DRC allows the end user to group silencers with similar hearing damage risk potential on a variety of weapon systems. After such grouping, further analysis can provide insight into the aforementioned phenomena. To that end, five silencers evaluated by PEW Science are included in this members-only Research Supplement to examine relative First Round Pop (FRP) and overall sound signature suppression performance characteristics. The silencers in this group were selected for their relevance to the above three rifle silencer technology classes. The five silencers behave differently, even despite some of them exhibiting similar performance quantified by the PEW Science Suppression Rating.  Their subsonic 300 BLK suppression performance provides an excellent case study comparing current rifle silencer technology.

Fig 1. PEW Science Suppression Rating Scale

The published Sound Signature Reviews of these five silencers, with subsonic 300 BLK ammunition, are linked below. Their technology class and subcategory or designation is noted:

Because the Suppression Rating is a DRC, it characterizes the postulated risk of hazard to bystanders, or the weapon operator, from a suppressed small arm weapon system. Despite achieving a similar Suppression Rating, some silencers may have certain signature characteristics that differ from others, and those differences are of interest to users, as noted above. Flow-Through, Total Signature Reduction, SURGE BYPASS, Forward Flux, and legacy baffle systems all respond differently to changes in muzzle blast pressure input.

Sound signature suppression is not the only performance attribute of interest to many users. Back pressure reduction is often paramount for reducing gas toxicity and weapon over-function. The higher flow rate models above do not represent an exhaustive list of silencers that may reduce back pressure; in addition to other existing silencers on the market, there exist new models such as the HUXWRX Ventum 762 and the Surefire SOCOM556-RC3. Both of these silencers are intended to exhibit higher gross flow rates, reduce over-function on reciprocating weapon systems, and reduce gas toxicity to the end user. The HUXWRX Ventum and Surefire RC3 use HUXWRX Flow-Through technology and a higher flow variant of Surefire Total Signature Reduction technology, respectively, to reduce back pressure. These two silencers will be evaluated by the PEW Science Laboratory at a later date.

In addition to flow rate, flash reduction, back pressure reduction, and overall signature suppression performance, sound suppression performance of centerfire rifle silencers, particularly during the first shot, is of significant concern to many weapon system operators. High sound signature amplitude during the first shot from a suppressed weapon system is referred to as First Round Pop (FRP). Prior to the weapon system being fired, a sound suppressor is filled with air from the surrounding environment; this air occupies the internal silencer volume and supports ancillary combustion during the first shot. It is this ancillary combustion that may increase sound signature relative to subsequent shots. The FRP phenomenon is present and measurable in all suppressed systems unless the internal silencer atmosphere is purged such that ancillary combustion is not supported within the silencer.

Fig 2. Suppression Rating Comparisons Of .30 Rifle Silencers Using PEW-SOFT 300 BLK Subsonic Test Data

Typically, silencers possessing a high flow rate also possess lower sound suppression performance with subsonic ammunition. However, there are significant exceptions. Hybrid designs have the potential to exhibit high performance in multiple regimes.

Although changes to gross gas flow rate (flow restriction, or back pressure) strongly correlates to sound signature suppression, there are other flow dynamics and frequency components of silencer sound signatures that result in varying signature severity to the human inner ear for a given suppressed system. These gas dynamics can significantly influence some signature characteristics. Furthermore, certain personnel may have preexisting hearing damage or other hearing sensitivity characteristics that differ from the 95th-percentile inner ear response with which the PEW Science Suppression Rating correlates. The impact of these differences on the human perception of silencer sound suppression performance has been quantified by PEW Science.

This research supplement is intended to provide more information to PEW Science members with regard to specific sound signature characteristics of the tested configurations in the aforementioned reviews and to help frame objective loudness comparisons between five 30 caliber rifle silencers that use various technologies to suppress subsonic 300 BLK sound signatures. Both FRP and total sound signature suppression regimes are examined. This supplement is part of ongoing PEW Science small arm weapon system sound signature research.

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