SSS.6.65 - Research Supplement: Taming the MK18, Part 1 - Surefire vs. OSS (Article Preview)
/The Surefire SOCOM556-RC2 with 3-Prong and WARCOMP, and the OSS HX-QD 556 on the MK18 5.56x45mm AR15 with 10.3-in Barrel
Two 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 two silencers were selected for their relatively high sound suppression performance; silencers exhibiting a relatively high PEW Science Suppression Rating (Figure 1) on the standard PEW Science MK18 test host weapon system described in Public Research Supplement 6.51.
Suppression Rating Rankings can be found in Section 7 of the Standard.
Fig 1. PEW Science Suppression Rating Scale
The below three silencer configurations are a small subset of those available for the MK18 weapon system on the current market. The Surefire SOCOM556-RC2 and the OSS HX-QD 556 represent significantly different technologies in the size and weight regime of interest that possess relatively high sound suppression performance on the MK18 platform. The published Sound Signature Reviews of these three silencer configurations, with supersonic ammunition on the aforementioned platform, are linked below:
Bolt-action weapons allow for the elimination of variables to study pure sound signature suppression phenomena. Other than sound transmission through the weapon system itself, there is one primary source of overpressure to atmosphere (the bare muzzle or silencer endcap, if equipped). The MK18, however, is an automatic rifle. During the firing of an automatic or semiautomatic AR15 weapon system, a second pressure pulse originates from the ejection-port of the weapon and it occurs early enough in time such that its waves coalesce with that of the muzzle signature. It is not ejection port signature, alone, that dictates the signature measured at the shooter’s head position when firing an AR15.
Given the two origins of overpressure from a suppressed automatic weapon system such as the MK18, the holistic sound signature to which the operator and bystanders are subjected is dependent upon the so-called pure suppression performance of the silencer, as well as the silencer’s flow rate. The balancing of the two performance attributes; the relationship between the system’s muzzle Suppression Rating and ear Suppression Rating, dictates overall performance.
In addition to the balance of flow rate and suppression parameters, silencer mounting schemes may significantly influence the parameters themselves. Silencer mounts may inherently change flow rate, leak gas introducing a tertiary origin of overpressure, or both. This phenomenon was observed and quantified in PEW Science testing of Surefire silencers with the WARCOMP mount in both 7.62 mm and 5.56 mm cartridge regimes, with both bolt-action and automatic rifles.
The Surefire SOCOM556-RC2 exhibits a relatively high muzzle Suppression Rating on the MK18. The OSS HX-QD 556 exhibits a relatively high ear Suppression Rating on the MK18. The published Suppression Rating data with the MK18, to date, is shown in Figure 2.
Fig 2. Suppression Rating Comparisons Of The HUXWRX HX-QD 556k, HX-QD 556, Trash Panda, R556, Razor, Saker 556 And The SOCOM556-RC2 , Using PEW-SOFT 5.56x45mm Supersonic Test Data
The interaction of muzzle signature and ejection port signature, as they coalesce and impact the shooter’s ear, is complex. Nonetheless, the Suppression Rating allows for the quantification of hearing damage risk to the weapon operator due to the combined signature; the quantity of origins of overpressure is inconsequential. Only the holistic signature measured during the full gunshot time regime is required.
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 three silencer configurations exhibiting high sound suppression performance on the MK18 weapon system. Both the FRP and average sound signature suppression regimes are examined. 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!
