SSS.6.56 - Research Supplement: The Quietest 308 Rifle Silencers - Detailed Sound Comparison (Article Preview)

Thunder Beast ULTRA 9, Otter Creek Labs PR30L, CGS Hyperion, and Dead Air Nomad-L on a .308WIN Bolt Action Rifle with 20-inch Barrel

Four 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 high sound suppression performance; silencers maximizing their PEW Science Suppression Rating (Figure 1) on a supersonic centerfire bolt action rifle. Silencers with suppression performance in this range typically have relatively high flow restriction, or back pressure, characterized by a relatively high PEW Science Omega Back Pressure Metric (Figure 2). Suppression Rating Rankings can be found in Section 7 of the Standard.

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Fig 1. PEW Science Suppression Rating Scale

The below is not an exhaustive list of so-called high performance rifle silencers on the current market, but is a relatively varied representation of available current technology in the size and weight regime of interest that possess extreme sound signature suppression. The published Sound Signature Reviews of these four silencers, with supersonic ammunition, are linked below:

• Thunder Beast ULTRA 9 (6.24)

• Otter Creek Labs PR30L (6.48)

• CGS Hyperion (6.27)

• Dead Air Nomad-L (6.55)

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, or 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. PEW Science Silencer Relative Back Pressure Metric, Omega, For 30 Caliber Rifle Silencers

Typically, silencers possessing a high Omega Metric exhibit high sound suppression performance, but there are several significant exceptions. Although gas flow rate reduction (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. 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 the four quietest supersonic 308 rifle silencers in the FRP and total sound signature suppression regimes. This supplement is part of ongoing PEW Science small arm weapon system sound signature research.

The full version of this article is only available to members. You can support PEW Science testing, research, and development with a membership, here. State-of-the-art firearm sound signature testing and research conducted by PEW Science is supported by readers like you. Thank you for your support!