SSS.6.157- Surefire SOCOM762-MINI2 and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle
/Surefire SOCOM762-MINI2 on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The SOCOM762-MINI2 is manufactured by Surefire. It is a 30 caliber centerfire rifle silencer, intended to suppress many cartridges with projectiles appropriately sized to travel through the bore, up to and including .300 Winchester Magnum. It has a 1.5-inch diameter and is 6.4 inches in length. The silencer mounts to the host firearm with a proprietary mounting system; the user may choose from various Surefire flash hider and muzzle brake mounts. The outer tube and end-cap are constructed of heat treated stainless steel. The baffles are constructed of Inconel steel alloy. As tested, the silencer weighs 16.6 ounces and the 3-prong flash hider weighs 4 ounces, for a total system weight of 20.6 ounces. The SOCOM762-MINI2 can be obtained from Silencer Shop.
The testing and analysis presented in this Sound Signature Review are of the SOCOM762-MINI2 on the MK18 Automatic AR15 rifle 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 6.157.1 contains SOCOM762-MINI2 test results and analysis using the SOCOM 3-Prong flash hider mount.
Section 6.157.2 contains a Surefire Total Signature Reduction Technology and mount Case Study, comparing the signatures generated by the SOCOM762-MIN2, SOCOM556-RC3, and SOCOM556-RC2 (Members Only).
Section 6.157.3 contains overall Suppression Rating comparisons of the SOCOM762-MINI2 with with dedicated 223 and 30 caliber silencers on the current market, including the KAC QDC/CRS-PRT, KAC QDC/MCQ-PRT, Surefire SOCOM556-RC3, Otter Creek Labs Polonium-30, AAC M4-2000 Mod 08, PTR VENT 3, SilencerCo Velos LBP, 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 6.157.4 contains an article summary and PEW Science laboratory staff opinions.
This review contains results with only the 3-Prong flash hider. The PEW Science laboratory has tested and analyzed the performance of several Surefire rifle silencers with both 3-Prong flash hider and WARCOMP closed-tine flash hider mounts. Through this comprehensive internal research, it was determined that WARCOMP-equipped Surefire systems exhibit a significant, persistent, and universal hazard increase to the system operator, independent of silencer, cartridge, or weapon system action type. This hazard increase results from uncontrolled early-time blast load propagation from a mount-interface leak, which is exacerbated by the WARCOMP ports in close proximity to the jet origin location. This phenomenon, and its influence on increased hazards to both system operators and bystanders, is investigated in the following analytical test report white papers:
PEW Science testing of the SOCOM556-RC2 on a 10.3-in barrel 5.56mm MK18 with both mounts (6.52).
PEW Science testing of the SOCOM556-RC2 on a 14.5-in barrel 5.56mm M4A1 with both mounts (6.128).
PEW Science testing of the SOCOM556-MINI2 on a 14.5-in barrel 5.56mm M4A1 with both mounts (6.144).
PEW Science testing of the SOCOM556-RC3 on a 10.3-in barrel 5.56mm MK18 with both mounts (6.151).
PEW Science has previously evaluated the SOCOM762-MINI2, as summarized in this report:
Cautions:
Although the SOCOM762-MINI2 has not been evaluated by PEW Science with the WARCOMP mount, it is also postulated that its performances with 7.62x51mm NATO, 5.56x45mm NATO, and subsonic 300 BLK are all negatively influenced by WARCOMP mount use for the same reasons detailed above. Therefore, end user caution is advised.
This is a 10.3-in barrel MK18 dataset. Performance is a function of holistic suppressed weapon system characteristics (the silencer in combination with the weapon). Extrapolation of testing and analytical results to and from different weapon systems may produce erroneous and potentially unconservative conclusions. Personnel hazards do not scale directly nor linearly between many host weapon systems.
The Surefire SOCOM762-MINI2 is identical in exterior dimensions to the SOCOM556-RC2. Despite these commonalities, the two silencers differ in both bore diameter and internal geometry. The performance of the two silencers on 5.56mm platforms is drastically different, as summarized in this report.
High Level Summary:
1. The hazard to the weapon system operator is somewhat increased with the 762-MINI2 over the 556-RC2, and the bystander hazard adjacent the muzzle is significantly increased. The severe distal jetting from the 762-MINI2 and subsequent blast wave coalescence at the operator’s head nullifies any ejection port blast load hazard reduction from the 762-MINI2’s higher flow rate (lower back pressure). This phenomenon is also evident when comparing the performance of the 726-MINI2 to that of the full-size SOCOM762-RC2 on the MK18.
2. When used with a closed-tine WARCOMP mount, the Surefire SOCOM762-MINI2 would most likely exhibit significantly reduced operator hazard mitigation, potentially being the lowest in the dataset. This postulation is based on the already severe muzzle blast wave coalescence at the operator’s head with the 3-Prong mount that would be exacerbated by an early-time WARCOMP leak-initiated shock load.
3. The Surefire Total Signature Reduction technology in the RC2 series, the MINI2 series, and modifications present in the RC3, are shown to produce less competitive performance on 5.56x45mm platforms than several competing designs when modified from the SOCOM556-RC2 baseline condition. The performance of Total Signature Reduction technology in Surefire rifle silencers does not scale linearly for length, baffle quantity, and bore diameter (See Member Case Study in Section 6.157.2).
Summary: When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Surefire SOCOM762-MINI2 mounted with the SOCOM 3-Prong flash hider achieved a composite Suppression Rating™ of 22.5 in PEW Science testing.
The supersonic .308 performance of the Surefire SOCOM762-MINI2 is detailed in previous Sound Signature Review 6.106, in which it achieved a Suppression Rating of 25.1 with the 3-Prong flash hider.
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
6.157.1 Surefire SOCOM762-MINI2 Sound Signature Test Results (SOCOM 3-Prong Flash Hider)
A summary of the principal Silencer Sound Standard performance metrics of the Surefire SOCOM762-MINI2 with the 3-Prong Flash Hider 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. Surefire SOCOM762-MINI2 (3-Prong FH) Sound Metric Summary
6.157.1.1 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 SOCOM762-MINI2 with the 3-Prong Flash Hider are shown in Figure 1a. The sound signatures of Shot 1, Shot 2, and Shot 3 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 Shots 2, 3, and 5.
Fig 1a. Surefire SOCOM762-MINI2 (3-Prong FH) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. Surefire SOCOM762-MINI2 (3-Prong FH) 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature
Figure 2a. Surefire SOCOM762-MINI2 (3-Prong FH) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. Surefire SOCOM762-MINI2 (3-Prong FH) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
The Surefire SOCOM762-MINI2 is almost identical in overall design envelope to the SOCOM556-RC2 and SOCOM556-RC3. The MINI2 designation, when applied to the 7.62mm Surefire SOCOM silencer family, mirrors the full-size 5.56mm SOCOM silencers in length. The 762-MINI2 shares more in common with the 556-RC2, in base technology. However, due to its over-bore for 5.56mm platforms and reduced baffle count, it also shares some performance similarities with the 556-RC3.
As a whole, hybrid designs possessing Surefire Total Signature Reduction Technology possess early proximal venting structures with dished baffles and progressive venting toward the distal end. One of the earliest forms of hybrid design technology in the PEW Science Silencer Sound Standard research taxonomy, the Surefire designs are highly sensitive to mount geometry, input jet characteristics, and bore size. The sensitivity of the SOCOM762-MINI2 to these parameters is highlighted in the above raw test data, which displays the following attributes:
Relatively expedient blowdown for a non-vented proximal geometry (Fig. 1a).
Significant coupled primary jet amplitude during first-round-pop (FRP), with consistent initial jet coupling, post-FRP (Fig. 1b).
Relatively long duration initial positive phase duration followed by continuous jetting post-FRP that subsides later in the shot string, after Shot 2. (Fig. 1b and Fig. 2).
PEW Science Research Note 1: For the MK18 weapon system, the Surefire rifle silencer forming the baseline performance standard is the Surefire SOCOM556-RC2, which was evaluated in report 6.52. In the same size envelope, changing parameters such as baffle spacing, quantity, primary bore size, and both proximal and distal vent arrays result in significant performance changes. These changes occur regardless of mount choice. In the cases of evaluations using the 3-prong flash hider mount, increasing proximal vent area with the introduction of a downstream proximal passive blast attenuator resulted in highly erratic first shot behavior. This was showcased in the laboratory evaluation of the Surefire SOCOM556-RC3 (6.151). In the present evaluation of the SOCOM762-MINI2, the parameters of bore size and baffle quantity are varied; both downstream expansion volume and axial flow area are increased. With these two increases, much of the same erratic behavior that was noted in the 556-RC3 evaluation results from the 762-MINI2 (see Research Note 2).
PEW Science Research Note 2: Despite the consumption of air supporting ancillary combustion during FRP, Shot 2 through the SOCOM762-MINI2 exhibits highly erratic post-peak blast load propagation and subsequent blast load impulse accumulation. Uncontrolled distal flow exhibited without purposeful venting is typically a negative performance characteristic of over-bore. Loss of efficiency by bore expansion is relatively commonplace, but not necessarily universal:
For example, the Otter Creek Labs Polonium-30 (6.143) provides an excellent case study demonstrating this phenomenon, as it is identical in all aspects other than bore size to its sister silencer, the Polonium (7.75). In the case of the traditional baffle Polonium design, it is shown to possess some scaling of performance as the bore size changes, without significant post-peak divergence (erratic behavior). The performance drops, but it is consistent.
One case of over-bore less significantly influencing performance is demonstrated by Surge Bypass hybrid technology found in the CAT ODB (6.120). Performances losses are uncharacteristically low for both overbore and different combustion regimes for this technology. Nonetheless, even in this advanced technology, cartridge-specific optimization proves to pay significant dividends as evidenced in the 5.56 performance evaluation of the smaller CAT WB (6.129).
Some technologies are extremely sensitive to such changes, including Surefire Total Signature Reduction implemented in the SOCOM762-MINI2. Other silencers demonstrating performance scaling issues with over-bore include the Q Trash Panda (6.61) in both pure suppression performance and consistency. Such inefficiencies are also characterized in measured impulse signatures from over-bored silencers in test reports featuring products such as the Rugged Razor762 (6.58), the Energetic Armament ARX (6.82); the Rugged Razor556 (6.76), and the Dead Air Sandman-S (6.92).
PEW Science Research Note 3: It is important to note that the severe muzzle blast and erratic behavior with the Surefire SOCOM762-MINI2 on the MK18 is not a function of mount. Although this type of blast propagation typically occurs with Surefire silencers that are equipped with WARCOMP mounts or excessive vent arrays, the behavior on the standard MK18 with the 762-MINI2 is driven entirely by the aforementioned internal design characteristics. A detailed comparison of blast and shock dynamics between multiple Surefire systems, illustrating this behavior, is provided to PEW Science Members in Section 6.157.2.
PEW Science Research Note 4: As a result of its fewer baffles and generous over-bore when compared to the Surefire SOCOM556-RC2, the SOCOM762-MIN2 exhibits lower back pressure. However, due to the method by which it achieves this higher gross flow rate, shooter hazard is only partially mitigated. Significant muzzle blast load propagation impacts the operator’s head, as detailed in Member Section 6.157.2. Hybrid design technologies do typically possess increased flow rate, either in early-time, late time, or both, through a variety of design features. Such designs are attractive for end users due to a lower degree of blast momentum transfer potential increase, giving way to less hazard near reflecting surfaces; a negative performance attribute of many Flow-Through design implemented in the HUXWRX FLOW series. In the case of the Surefire Total Signature Reduction hybrid technology in the 762-MIN2, flow rate increase comes at a cost. For a discussion of other various back pressure-reducing designs present in silencers with high early time or late time flow rates (or both), see PEW Science Member Research Supplement 6.124. This supplement provides an overview summary of Flow-Through, Total Signature Reduction, SURGE BYPASS, and Forward Flux technologies.
Although the SOCOM762-MINI2 reduces backpressure, and may somewhat reduce blow-back to the weapon operator on some host weapons when compared to the use of a SOCOM556-RC2, blast overpressure hazard reduction may not be significantly reduced. Furthermore, it is important to note that the FRP behavior from the SOCOM762-MINI2 is persistent for two shots in both blast load impulse accumulation and both bystander and operator overpressure hazard risk.
PEW Science Research Note 5: 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 87 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 6: The closing time of the AR15 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.
The shape, timing, and magnitudes of the early-time pressure pulses and overall shape of the impulse waveforms measured at the muzzle, from shot-to-shot, are relatively consistent. The consistency of the waveform amplitudes highlight the silencer’s overall sound performance consistency at the muzzle after the FRP, as well as the relative consistency of the tested automatic rifle firearm configuration.
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 7: Note that the muzzle Suppression Rating of the SOCOM762-MIN2 with the 3-Prong mount is 17.2 and the at-ear Suppression Rating is 20.4; the same zone on the Suppression Rating Dose Chart. The lower back pressure of the SOCOM762-MINI2 compared with the SOCOM556-RC2 contributes to a less severe ejection port blast signature. However, the more severe muzzle blast from the 762-MINI2 nullifies the reduction in ejection port blast hazard to the shooter on the standard MK18 weapon system. The WARCOMP mount may further increase this shooter hazard, as discussed in the report introduction.
The signatures measured at the shooter’s ear are presented below.
6.157.1.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 6-shot test 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 6 shots are shown in Figure 3. The primary sound signature history is shown in Figure 3a. An annotated timescale is displayed in Figure 3b, for Shots 1, 2, and 3. The real sound impulse (momentum transfer potential) histories at the ear from the same 6-shot test are shown in Figure 4. Again, full and shorter timescales are shown.
Figure 3a. Surefire SOCOM762-MINI2 (3-Prong FH) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature
Figure 3b. Surefire SOCOM762-MINI2 (3-Prong FH) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 4a. Surefire SOCOM762-MINI2 (3-Prong FH) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature
Figure 4b. Surefire SOCOM762-MINI2 (3-Prong FH) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature Peaks
For the first time in PEW Science laboratory testing of Surefire silencers, the signature at the shooter’s ear from a 3-prong equipped silencer is demonstrating significantly high amplitude pre-peak blast load propagation. Note the following raw blast load waveform features above:
Significant muzzle blast in early time (Fig. 3b)
Coincident rarefaction after early time positive phase jetting (Fig. 3b).
Severe initial jet momentum accumulation (approximately 29 ms, Fig. 4b).
Significant latent accumulation in Shots 1 and 2 (Fig. 4b).
This behavior has previously only been observed in WARCOMP mount tests and RC3 vented model tests. The reader is encouraged to examine the shooter-ear impulse accumulation plots in the referenced WARCOMP and RC3 tests at the beginning on this report, for comparison. Further detailed comparison is provided in Section 6.157.2.
PEW Science Research Note 8: The signatures measured at the operator’s head from the 762-MINI2 have direct relation to those measured in the free field, presented in the previous section. For example, expedient blowdown is noted in Figure 3a. However, additionally, the operator is subjected to ejection port blast load at a close proximity, which is nested with the blast loads from muzzle signature propagation, and in addition to the pre-peak severe blast loads noted above, the late-time erratic momentum accumulation of Shot 2 is also mirrored at the shooter’s ear (Figure 4).
As previously referenced throughout the Standard, front-loaded blast impulse accumulation is often noted in tuned or low-backpressure systems, as a result of muzzle blast wave energy “outrunning” that of ejection port pulse. Although that phenomenon is still present in this test, indicating the benefits of the 762-MINI2 lower back pressure behavior, the severe muzzle blast overwhelms the signatures, nullifying any overpressure mitigating benefits of the silencer’s flow rate. On this host weapon, this in direct contradiction to the performance statements by the manufacturer in their website literature. Therefore, use caution is advised. It should be noted that the silencer is marketed for use on 7.62mm weapons. However, this type of behavior may not necessarily be limited to 5.56mm hosts.
The shift of relative FRP impulse timing is also influenced by FRP severity. As a result, so-called balanced designs may display both front-loaded and back-loaded FRP impulse phenomena. These types of designs may excel at FRP suppression, have high early-time flow rate, and may control momentum propagation in the free field, resulting in overall “high performance.” An example of such silencers is the previous generation SOCOM556-RC2 (see Fig. 4b, 6.52.1.2). A modern, more extreme example of balanced high performance is the CAT WB (see Fig. 4b, 6.129.1.2).
PEW Science Research Note 9: The Surefire SOCOM762-MINI2 possesses only limited “balanced” performance attributes discussed above, in a gross sense. There are two significant differences between 762-MIN2 performance at the operator’s location when compared to that of the other two aforementioned silencer examples (RC2 and WB), with some parallels to comparison with the RC3:
Like the the RC3, the 762-MINI2 has significantly more intense muzzle blast than the RC2 and WB. This increases operator hazard, particularly away from the free field (indoors, near barriers, etc).
Also like the RC3, the 762-MINI2’s first round signatures are potentially erratic. This pushes blast load positive phase impulse accumulation further to late-time (Fig. 4b); a phenomenon typically only seen in high back pressure systems. Although both the 762-MIN2 and RC3 are “low back pressure,” the hazard to the operator may be similar to firing a high back pressure silencer on the same weapon system, during the first shots.
As discussed in Research Note 4, the 762-MINI2 does subject shooters to less “gas blow back” than the standard 556-RC2 design. This performance attribute may be attractive to some users. However, there exist other high performance silencers with balanced design attributes and dedicated bores that control late-time gas momentum propagation in a superior fashion, like the CAT WB (6.129) and PTR VENT 3 (6.135). As it stands, in the current PEW Science research pedigree, the holistic suppression performance of over-bored models like the 762-MINI2 is lower than that of several other designs on the standard MK18, including those with high flow rate. Such designs include the HUXWRX FLOW 762 Ti, CAT ODB and WB, SilencerCo Velos, Liberty Precision Machine Torch, PTR VENT 3, and others.
The 762-MINI2, 556-RC3, as well as the previous generation 556-RC2 (both full-size and MINI2 systems) present a relatively “balanced” shooter’s ear signature on this weapon system, when considering the contributions from both muzzle blast and ejection port blast to the hazard, with the 3-Prong flash hider. In previous silencer generations, using a ported WARCOMP flash hider induced ancillary blast load propagation potential due to the Surefire mounting system possessing a relatively poor seal, further increasing shooter hazard. However, it is important to note that due the over-bore of the 762-MINI2 and its overall size, the some of the same erratic behavior noted in WARCOMP use is observed with the 3-Prong mount. This reduces the nature of the “balanced” design. This is highlighted in the below Member case study.
6.157.2 Surefire SOCOM762-MIN2, 556-RC3, and 556-RC2 Comparison Case Study
Below, direct comparisons of the measured pressure and impulse waveforms with multiple mounts used in five tests of the Surefire silencers are shown. This is further members-only analysis; 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!
6.157.2.1 Muzzle Signature Variations with Silencer
Figure 9a and Figure 9b show first shot muzzle overpressure and impulse comparisons, respectively, of three Surefire rifle silencer tests (the SOCOM556-RC3, SOCOM556-RC2, and SOCOM762-MINI2, respectively). These comparisons directly illustrate the similarities and differences in gas dynamics at the muzzle in Surefire Total Signature Reduction Technology due to:
Proximal and distal vent arrays (556-RC3)
Overbore and baffle spacing (762-MINI2).
Baffle quantity and dedicated bore (556-RC2).
Note that Figure 9 displays FRP behavior of the three silencers with the 3-Prong flash hider mount.
Fig 9a. Surefire SOCOM Silencer (3-Prong FH) 5.56x45mm NATO MK18 FRP Muzzle Pressure Mount Comparison
Fig 9b. Surefire SOCOM Silencer (3-Prong FH) 5.56x45mm NATO MK18 FRP Muzzle Impulse Mount Comparison
All data is mount-controlled (the 3-Prong flash hider mount was used in all three tests displayed in Figure 9). The data is also length and diameter controlled (each of the three silencers is the same length and diameter). During FRP, two phenomena are persistent with venting or over-bore:
Significant initial jetting.
Significant post-peak muzzle blast impulse accumulation.
These phenomena are clearly visible in both pressure space (Fig. 9a) and impulse space (Fig. 9b). In the case of significant proximal expansion chamber to annulus to the downstream distal passive blast attenuator vent array (RC3), rapid combustion propagation through the void space is shown to occur in many cases regardless of mount. In the case of significant over-bore and baffle spacing, similar effects are noted, with a higher amplitude (762-MINI2).
Shot 2 signatures with the same three systems are compared below, in both pressure space (Fig. 10a) and impulse space (Fig. 10b). Note the significant similarities in mount signatures during Shot 2, when compared to those during FRP. However, note the persistent late-time blast load impulse propagation from the 762-MINI2.
Fig 10a. Surefire SOCOM Silencer (3-Prong FH) 5.56x45mm NATO MK18 Shot 2 Muzzle Pressure Mount Comparison
Fig 10b. Surefire SOCOM Silencer (3-Prong FH) 5.56x45mm NATO MK18 Shot 2 Muzzle Impulse Mount Comparison
PEW Science Research Note 10: Inefficiencies on the MK18 platform from gross flow rate increases without adequate turbulence generation and heat transfer can result in distal blast propagation that presents as “uncontrolled.” In the case of the SOCOM556-RC3, this is common during initial shots due to the mechanism by which venting feeds the unobstructed annulus. In the case of the SOCOM762-MINI2, the phenomena presents similarly but for a different reason. Rather than secondary path blast propagation, the 762-MINI2 exhibits severe primary bore flow through the entire silencer length. Any propensity for rapid pressurization of the RC2-series annular cavities in the 762-MINI2 is minimized by the over-bore for the smaller diameter 5.56x45mm combustion jet. The technology does not scale with consistency for over-bore, even when longer; see full size Surefire SOCOM762-RC2 MK18 testing (6.73). The much longer silencer does quench ancillary combustion post-FRP, however.
Due to the uncontrolled distal blast propagation from the short over-bored 762-MINI2, high risk phenomena may present to the weapon operator, not unlike that seen in WARCOMP use. This is examined below.
6.157.2.2 Shooter’s Ear Signature Variations with Mount
Figure 11a and Figure 11b show Shot 2 shooter’s ear blast pressure and blast impulse comparisons, respectively. These comparisons directly illustrate the signature similarities to the operator between use of the WARCOMP mount with the RC3 and the RC2, and the 3-prong flash hider equipped 762-MINI2 on the MK18 host weapon.
Fig 11a. Surefire SOCOM Silencer 5.56x45mm NATO MK18 Shot 2 Ear Pressure Mount Comparison
Fig 11b. Surefire SOCOM Silencer 5.56x45mm NATO MK18 Shot 2 Ear Impulse Mount Comparison
In pressure space (Fig. 11a), the 762-MINI2 exhibits significant initial jetting that propagates to the shooter’s head. However, it is important to note that the type of blast load is different than that generated by the WARCOMP leak in the RC2 and RC3 systems. The blast load differs in both rise time and amplitude. However the blast load also differs in duration; the initial propagation of the wave has a significantly longer positive phase. As a result of these different blast load wave dynamics, almost equivalent blast load momentum transfer potential at the operator’s head results (Fig. 11b, approximately 28.5 ms).
The above hazard potential from the 762-MINI2, and its impulse hazard severity similarity to that of a persistent mount blast load leak in WARCOMP systems, illustrates the potential severity of over-bore silencer use on short barrel 5.56mm weapon platforms. The flow rate is increased due to overbore, which decreases the severity of ejection port blast loads, as discussed in the previous section. However, the significant distal propagation of muzzle blast waves completely nullify this benefit to the operator. This is the primary reason why the Suppression Rating at the operator’s head is not able to rise with the 762-MINI2 despite “low ejection port blast due to low back pressure.” Note that the 762-MINI2 continues to exhibit late time blast impulse propagation (30.5 ms, Fig. 11b), despite the signature occurring post-FRP.
These impulse curve comparisons highlight how ejection port blast, WARCOMP leak blast, and end cap blast, all combine to increase shooter’s ear hazard. All blast loads have discrete origins with additive terminal effects.
In summary, when using the 762-MINI2 on the MK18, the design results in blast load propagation that is so severe, it may mimic increased operator hazards typically seen from WARCOMP mount leaks. This phenomenon nullifies any ejection port blast load propagation reduction from its higher gross flow rate. The performance of Total Signature Reduction technology in Surefire rifle silencers does not scale linearly for length, baffle quantity, and bore diameter. The reader is also encouraged to examine the 7.62x51mm testing of the 762-MINI2 in report 6.106.
This concludes the Surefire Total Signature Reduction Member Case study portion of this report. Gross Suppression Rating comparisons of silencers tested on the MK18 in the public research pedigree are provided below.
6.157.3 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 12 presents a comparison of the PEW Science Suppression Rating of the Surefire SOCOM762-MINI2 with the 3-Prong Flash Hider mount with that of several other silencers on the MK18 weapon system. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Figure 12. Suppression Rating Comparisons of the Surefire SOCOM762-MIN2 and other rifle silencers, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis
Figure 12 presents an overall summary of the postulated hazards to the operator and bystanders when fielding a variety of different silencers on the standard MK18 weapon system. The Surefire SOCOM762-MINI2 with the 3-prong flash hider from this test program is shown in red. Hazards are expressed with the Suppression Rating; a holistic parameter that captures human inner ear damage risk potential from a measured impulsive complex 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. The PEW Science Suppression Rating is a damage risk criterion (DRC), a lower Suppression Rating indicates a higher personnel hazard in the free field - it is not a subjective quantity; it is an objective quantification of hearing damage risk potential.
The following gross conclusions can be made from the above:
The Surefire SOCOM762-MINI2 with the 3-prong flash hider produces a more severe free field hazard than the SOCOM556-RC2 with the same mount on the same weapon system. The hazard to the weapon system operator is somewhat increased with the 762-MINI2 over the 556-RC2, and the bystander hazard adjacent the muzzle is significantly increased. The severe distal jetting from the 762-MINI2 and subsequent blast wave coalescence at the operator’s head nullifies any ejection port blast load hazard reduction from the 762-MINI2’s higher flow rate (lower back pressure). This phenomenon is also evident when comparing the performance of the 726-MINI2 to that of the full-size SOCOM762-RC2 (6.73) on the MK18.
The free field bystander hazard reduction with a 3-Prong mounted Surefire SOCOM762-MINI2 is similar to that of a KAC QDC/MCQ-PRT with 3 Prong Mount (6.156), Energetic Armament ARX (6.82), and Rugged Razor762 (6.58) on the standard MK18 weapon system.
The free field shooter’s ear hazard reduction with a Surefire SOCOM762-MINI2 is similar to that of an Otter Creek Labs Polonium-K (6.95), AAC M4-2000 Mod 08 (6.139), and Dead Air Sandman-S (6.92). Again, despite the 762-MINI2’s high flow rate that reduces ejection port blast hazard, its muzzle blast is severe enough such that the level of protection to the weapon operator is reduced.
When used with a closed-tine WARCOMP mount, the Surefire SOCOM762-MINI2 would most likely exhibit significantly reduced operator hazard mitigation, potentially being the lowest in the dataset. This postulation is based on the already severe muzzle blast wave coalescence at the operator’s head with the 3-Prong mount that would be exacerbated by an early-time WARCOMP leak-initiated shock load.
The over-bore and baffle spacing in the Surefire SOCOM762-MINI2 results in significant performance deficiencies for the 5.56x45mm MK18 platform. Other silencers demonstrating performance scaling issues with over-bore include the Q Trash Panda (6.61) in both pure suppression performance and consistency. Such inefficiencies are also characterized in measured impulse signatures from over-bored silencers in test reports featuring products detailed above, as well as the such as the Rugged Razor556 (6.76).
PEW Science Research Note 11: The Surefire Total Signature Reduction technology in the RC2 series, the MINI2 series, and modifications present in the RC3, are shown to produce less competitive performance on 5.56x45mm platforms than several competing designs when modified from the SOCOM556-RC2 baseline condition. When modified for a high flow rate with over-bore (762-MINI2) or with enhanced proximal and distal vent arrays (RC3), performance deficiencies are noted. Of the high flow rate designs on the current market, including so-called hybrid designs in which high early time flow rate is throttled to control later time gas momentum propagation, such modifications provide lower overall performance than that implemented in the previous generation RC2 series. When compared to more advanced technologies (CAT SURGE BYPASS, HUXWRX Flow-Through, and PTR PIP, for example), these technology modifications are significantly outperformed in several metrics and gross blast and shock dynamics.
As detailed in this report, 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. The evaluations of the Surefire SOCOM762-MINI2 detailed in this report exemplify the limits of applicability of 7.62mm silencer over-bore conditions to 5.56mm short barrel rifle suppression. Uncontrolled distal flow rate significantly influences weapon operator hazard reduction efficacy.
Small arm weapon system suppression performance is a spectrum. The PEW Science Suppression Rating and the Silencer Sound Standard help quantify this spectrum for end users and industry, objectively.
6.157.4 Review Summary: Surefire SOCOM762-MINI2 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 Surefire SOCOM762-MINI2 mounted with the SOCOM 3-Prong flash hider achieved a composite Suppression Rating™ of 22.5 in PEW Science testing.
The supersonic .308 performance of the Surefire SOCOM762-MINI2 is detailed in previous Sound Signature Review 6.106, in which it achieved a Suppression Rating of 25.1 with the 3-Prong flash hider.
As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Laboratory Staff Opinion:
The Surefire SOCOM762-MINI2 is a compact 30 caliber machine gun rated rifle silencer that possesses reduced sound signature suppression performance compared with many larger 7.62 silencers on the market, while possessing significantly reduced back pressure. The silencer may also be used on 5.56 weapon platforms; relative to dedicated 5.56 silencers, it may be considered full-size. The 762-MINI2 is identical in size to the 556-RC2, but exhibits significantly lower performance on 5.56 systems.
The SOCOM762-MINI2 utilizes a similar internal design to other silencers in the Surefire SOCOM family such as the Surefire SOCOM762-RC2 (the full size version of the silencer) and the Surefire SOCOM556-RC2. The SOCOM-RC and -MINI subfamilies of silencers utilize vented dished baffles along with early venting in the first expansion (blast) chamber; it is through these geometric attributes that the silencers exhibit relatively high flow rate for their design envelopes. However, the combustion pressure and duration from the 7.62x51mm cartridge overwhelms this design if baffle quantity is significantly reduced. In this program, 5.56x45mm combustion is also shown to overwhelm the design, highlighting scaling irregularities of over-bore and baffle spacing for the Total Signature Reduction technologies in Surefire rifle silencers.
This study specifically highlights the lack of performance scaling that is possible for 30-caliber silencers on 5.56x45mm platforms. With the standard MK18, the hazard to the weapon system operator is somewhat increased with the 762-MINI2 over the 556-RC2, and the bystander hazard adjacent the muzzle is significantly increased. The severe distal jetting from the 762-MINI2 and subsequent blast wave coalescence at the operator’s head nullifies any ejection port blast load hazard reduction from the 762-MINI2’s higher flow rate (lower back pressure). This phenomenon is also evident when comparing the performance of the 726-MINI2 to that of the full-size SOCOM762-RC2 on the MK18. When used with a closed-tine WARCOMP mount, the Surefire SOCOM762-MINI2 would most likely exhibit significantly reduced operator hazard mitigation, potentially being the lowest in the dataset. This postulation is based on the already severe muzzle blast wave coalescence at the operator’s head with the 3-Prong mount that would be exacerbated by an early-time WARCOMP leak-initiated shock load. Finally, the Surefire Total Signature Reduction technology in the RC2 series, the MINI2 series, and modifications present in the RC3, are shown to produce less competitive performance on 5.56x45mm platforms than several competing designs when modified from the SOCOM556-RC2 baseline condition. The performance of Total Signature Reduction technology in Surefire rifle silencers does not scale linearly for length, baffle quantity, and bore diameter.
Only the SOCOM 3-Prong flash hider was used in the testing of this silencer. PEW Science has presented a significant amount of test data and analysis demonstrating the comprised suppression performance of the WARCOMP mount and increased hazards to the weapon operator. Surefire advises that the WARCOMP mount, while able to be used with the SOCOM762-MINI2, is intended for operators that are using their weapon unsuppressed and may use their silencer to suppress their weapon system infrequently. The WARCOMP provides an enhancement to shooting dynamics when unsuppressed, and these benefits are part of the intended design. Note that PEW Science has not performed an in-depth evaluation of the WARCOMP without a silencer mounted. For users that may only seldomly suppress their weapon system, the WARCOMP mount may offer benefits that make it an attractive choice.
The use of the Surefire locking collar is relatively straight forward. Note that some users have indicated carbon build-up on the mount that may prevent an operator from removing the silencer. Furthermore, carbon buildup may result in the silencer not being properly aligned upon reattaching; this misalignment may result in baffle strikes. PEW Science has experienced this in testing and highly recommends users of the Surefire mounting system clean their mounts regularly.
In this review, the Surefire SOCOM762-MINI2 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.
