SSS.6.73 - Surefire SOCOM762-RC2 and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle
/Surefire SOCOM762-RC2 on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The SOCOM762-RC2 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 8.4 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 20.7 ounces and the 3-prong flash hider weighs 4 ounces, for a total system weight of 24.7 ounces. The SOCOM762-RC2 can be obtained from Silencer Shop.
This review contains results from two separate tests. PEW Science tested the SOCOM762-RC2 on the MK18 with the SOCOM 3-Prong flash hider mount and also with the WARCOMP closed-tine flash hider mount. The SOCOM 3-Prong flash hider mount is non-ported and contains so-called “labyrinth seals.” The presence of the seal rings, and more importantly the lack of ports, results in the 3-prong flash hider system exhibiting significantly different gas dynamics than does a ported WARCOMP-equipped SOCOM762-RC2 system. Similar phenomena were measured and analyzed with 7.62x51mm NATO ammunition in the PEW Science test of the SOCOM762-RC2 on a bolt-action rifle in Sound Signature Review 6.26, as well as in the PEW Science test of the SOCOM556-RC2 on the MK18 automatic AR15 rifle in Sound Signature Review 6.52.
Caution: PEW Science does not recommend the WARCOMP mount for prolonged suppressed use, for most operators. Personal protective equipment (PPE), including eye and ear protection, is recommended for the operation of suppressed small arms, in general.
Both sets of test results in this Sound Signature Review are of the SOCOM762-RC2 on the MK18 automatic AR15 rifle, chambered in 5.56x45mm NATO with a 10.3-inch barrel. Federal XM193 55gr ammunition was used in the tests. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Section 6.73.1 contains test results using the SOCOM 3-Prong flash hider mount.
Section 6.73.2 contains test results using the WARCOMP closed-tine flash hider mount.
Section 6.73.3 contains an in-depth comparison of the sound signatures and gas dynamics of the two mount systems.
Section 6.73.4 contains Suppression Rating comparisons of the two systems, and of other silencers on the MK18.
Section 6.73.5 contains the review summary and subjective PEW Science opinions.
Summary: When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Surefire SOCOM762-RC2 mounted with the SOCOM 3-Prong flash hider achieved a composite Suppression Rating™ of 24.9 in PEW Science testing. When mounted with the WARCOMP flash hider on the same host weapon and fired with the same ammunition, the SOCOM762-RC2 achieved a composite Suppression Rating of 22.8. As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
The supersonic .308 performance of the Surefire SOCOM762-RC2 is detailed in previous Sound Signature Review 6.26, in which it achieved a Suppression Rating of 38.4 with the 3-Prong and 24.8 with the WARCOMP.
The subsonic 300 BLK performance of the SOCOM762-RC2 is detailed in previous Sound Signature Review 6.46, in which is achieved a Suppression Rating of 44.0.
Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings
6.73.1 SOCOM762-RC2 Sound Signature Test Results (SOCOM 3-Prong Flash Hider)
A summary of the principal Silencer Sound Standard performance metrics of the SOCOM762-RC2 tested 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-RC2 (SOCOM 3-Prong Flash Hider) Sound Metric Summary
6.73.1.1 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 dataset and bolt-closing signatures. 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.
The primary sound signature pressure histories for all 6 shots with the SOCOM762-RC2 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 5-shot test are shown in Figure 2a. In Figure 2b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shot 2 and Shot 3.
Fig 1a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature
Figure 2a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
The pressure and impulse waveforms shown in Figure 1 and Figure 2, respectively, share many similarities with those measured during the firing of the same SOCOM762-RC2 silencer through a bolt-action rifle with 7.62x51mm NATO ammunition in Review 6.26. The measured first-round-pop (FRP) is visible in both the pressure and impulse regimes, in peak amplitudes, timing, and wave shapes, as is typical from a suppressed rifle. It should be noted that although the measured overpressure and impulse amplitudes during FRP in the free field are significant in this test, their gross influence on overall hearing response severity to bystanders (muzzle Suppression Rating) is not significant. Therefore, PEW Science postulates FRP to be noticeable to bystanders from this silencer on the MK18, but the hearing damage risk to bystanders to be similar to that from subsequent shots.
PEW Science Research Note 1: The initial early-time pressure histories shown in Figure 1b are very similar to those measured from the Surefire SOCOM762-RC2 silencer in Review 6.26 fired on a bolt-action rifle. However, the SOCOM762-RC2 is significantly over-bored for the 5.56x45mm weapon platform. This geometric difference between it and its sister silencer, the Surefire SOCOM556-RC2 (Review 6.52), results in significant signature differences when the SOCOM762-RC2 is used on the MK18 weapon system. FRP signature significantly increases; though the hearing damage potential to bystanders is similar, the higher flowrate of the larger bore is most easily discernable in Shot 1 impulse (Figure 2b). The consistency of the signatures in the impulse regime, after the first shot, is notable; consistent sound signatures from rifle silencers exhibiting significant over-bore on a weapon platform are atypical. For example, the SOCOM762-RC2 produces much more consistent sound signatures than do other 30 caliber silencers tested on the MK18 platform, such as the Rugged Razor (Review 6.58) and Q Trash Panda (Review 6.61). The SOCOM762-RC2 is also more consistent than the CGS Helios QD (Review 6.66) on this platform. It is important to note that both the Trash Panda and the Helios QD are quieter than the SOCOM762-RC2 on the MK18, on average, despite the differences in signature consistency.
PEW Science Research Note 2: Surefire rifle silencers, while sharing some similarities, possess differing design features across model lines. For example, the SOCOM762-RC2 and SOCOM300-SPS are both full-size 30 caliber silencers, but exhibit completely different gas dynamics due to different baffle designs. Whereas the SOCOM762-RC2 exhibits higher flow rate (lower back pressure) suitable for use on semiautomatic host weapons with 7.62x51mm ammunition, the Surefire SOCOM300-SPS exhibits lower flow rate (higher back pressure) suitable for use in suppressing subsonic intermediate rifle cartridges like 300 BLK. Their sister silencer, the SOCOM556-RC2, is significantly different in flow rate and performance on the MK18.
PEW Science Research Note 3: The higher flow rate through the SOCOM762-RC2 than the 5.56mm SOCOM556-RC2 occurs despite the longer length of the 7.62mm silencer and its greater number of baffles. This phenomenon highlights the significant influence of over-bore to silencer behavior, as well as the inherently high flow rate (low backpressure) of the SOCOM762-RC2 design. The low backpressure of the Surefire SOCOM762-RC2, and its implications in different flow regimes, are discussed in its subsonic 300 BLK test report in Section 6.46.3 of Sound Signature Review 6.46.
PEW Science Research Note 4: While a second pressure pulse originates from the ejection-port signature of the weapon, it occurs early enough in time such that its waves coalesce with that of the muzzle signature. However, in late time (at approximately 85 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 5: The closing time of the MK18 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. 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.
Note that the muzzle Suppression Rating of the Surefire SOCOM762-RC2 with the 3-Prong Flash Hider is 21.9 and the at-ear Suppression Rating is 21.0; the same zone on the Suppression Rating Dose Chart. The high flow rate of the Surefire SOCOM762-RC2 assists with reducing ejection port signature, but its muzzle signature is severe enough to increase the overall severity of the signature to the shooter. The use of the WARCOMP mount changes the gas dynamics, and thus the suppression performance, of the SOCOM762-RC2 on this platform. This phenomenon is explored in Section 6.73.2 of this review.
6.73.1.2 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 5 shots are shown in Figure 3. 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 4. Again, full and short timescales are shown.
Figure 3a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature
Figure 3b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 4a. SOCOM556-RC2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature
Figure 4b. SOCOM556-RC2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature Peaks
Unlike in the measurements at the muzzle, the FRP from the SOCOM762-RC2 at the shooter’s ear is significant enough to be immediately noticeable to the shooter, and may not diminish until after the third shot. This phenomenon is atypical, and most often occurs with significant over-bore and high flow rate silencers. Like in the measurements at the muzzle, there are waveform indicators measured at the ear consistent with low back pressure (low flow restriction; low PEW Science Omega Metric). Of significant note is the pronounced late-time impulse during Shot 1 (Figure 4). The SOCOM762-RC2 has a flow rate that is high enough to produce this significant FRP, but uniform enough to produce consistency in subsequent shots. As previously stated in Research Note 1, this behavior is atypical.
Significant difference at the shooter’s ear is noted in the behavior between the SOOM762-RC2 and the Rugged Razor, the Q Trash Panda, and even the CGS Helios QD on the MK18. Like noted at the muzzle, there is erratic impulse behavior, indicative of significant silencer over-bore. However, the variation is not as significant with the SOCOM762-RC2 as it is with those other 30 caliber silencers. Notably, the secondary combustion phenomena from the short (10.3-in) MK18 host weapon barrel is suppressed effectively. Research Supplement 6.51 illustrates this secondary blast, unsuppressed in the free field. Note that this secondary blast may not always be as effectively suppressed with the WARCOMP mount (See Section 6.73.2 of this review, below).
PEW Science Research Note 6: Shorter than the 20-in barrel bolt-action rifle host weapon, the 10.3-in barrel automatic rifle places the blast source in closer proximity to the shooter’s ear. In addition to the silencer endcap being closer, the ejection port allows combustion products at higher than atmospheric pressure to vent relatively suddenly in the time regime of so-called chamber blow-down. This venting time, and thus the vented pressure amplitude and wave shape, varies depending upon the pressure history in the chamber and barrel, which are in turn dependent upon the flow restriction (back pressure) of the silencer. Both the close proximity of the muzzle to the shooter’s ear, and the additive ejection port pressure coalescing with the muzzle signature wave front(s), result in a more severe signature at the shooter’s ear than 1.0 m left of the weapon muzzle. Therefore, the at-ear Suppression Rating is lower than the muzzle Suppression Rating with this particular silencer on the MK18 host weapon.
Data acquired with the WARCOMP-equipped weapon system follows.
6.73.2 SOCOM762-RC2 Sound Signature Test Results (WARCOMP Flash Hider)
A summary of the principal Silencer Sound Standard performance metrics of the SOCOM762-RC2 tested with the WARCOMP Flash
Hider is shown in Table 2. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. As stated in Section 6.73.1, 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 2. Surefire SOCOM762-RC2 (WARCOMP Flash Hider) Sound Metric Summary
6.73.2.1 SOUND SIGNATURES AT THE MUZZLE
Real sound pressure histories from the second 6-shot test with the SOCOM762-RC2 acquired with PEW-SOFT™ are shown below, this time with the closed-tine WARCOMP flash hider. 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 sixth shot signatures are displayed in the data presentation but are not included in the analysis to maintain consistency with the overall PEW Science dataset and bolt-closing signatures. 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.
The primary sound signature pressure histories for all 6 shots with the SOCOM762-RC2 on the WARCOMP are shown in Figure 5a. The sound signatures of Shot 1, Shot 2, and Shot 3 are shown in a smaller time window in Figure 5b. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 6a. In Figure 6b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shot 2 and Shot 3.
Fig 5a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle WARCOMP Muzzle Sound Pressure Signature
Fig 5b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle WARCOMP Muzzle Sound Impulse Signature
Figure 6a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle WARCOMP Muzzle Sound Impulse Signature
Figure 6b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle WARCOMP Muzzle Sound Impulse Signature
As was shown in the test with the 3-Prong Flash Hider, the measured first-round-pop (FRP) with the WARCOMP mount is evident in both pressure and impulse space (Figure 5 and Figure 6, respectively).
As was observed in bolt-action rifle testing with the Surefire SOCOM762-RC2 silencer, irregularities in the wave shapes occur with the WARCOMP, when compared to the test using the 3-Prong Flash Hider. Direct comparisons are provided in Section 6.73.3 of this review. In addition to these irregularities, the overall late-time shapes of the impulse waveforms measured at the muzzle, from shot-to-shot, are less consistent than with the 3-prong flash hider, highlighting possible anomalies in gas dynamics that may occur when using an over-bored silencer with a mount that leaks high pressure gas. Note the highly irregular early-time gas jetting in Figure 5b, beginning at a time of 29.7 ms. This is high pressure gas leakage from the silencer mount interface, originating from the WARCOMP mount ports, as measured 1.0 m left of the silencer end cap. Multiple pressure pulses are measured.
PEW Science Research Note 7: The muzzle sound signature of the SOCOM762-RC2 is slightly more severe when using the WARCOMP mount. A much more significant difference in signature, to bystanders, occurs with the SOCOM556-RC2 when using the WARCOMP mount (see Review 6.52). The greater bystander risk of WARCOMP use with the SOCOM556-RC2 than with the SOCOM762-RC2 is primarily due to overall mass flow rate (back pressure) differences between the two silencers. Regardless of the Surefire silencer used, even if the measured peak pressure and impulse amplitudes are not significantly different, the wave shapes and their durations vary. There is a significant change in gas dynamics with the WARCOMP mount due to early-time gas venting from the mount interface. Again, Section 6.73.3 of this review contains direct comparison of the WARCOMP and 3-Prong Flash Hider.
The gas jetting out of the mount interface with the WARCOMP increases the severity of the sound signature to bystanders and lowers the muzzle Suppression Rating slightly to 21.7. Note that the at-ear Suppression Rating of the SOCOM762-RC2 with the WARCOMP mount on the MK18 occupies an even lower zone on the Suppression Rating Dose Chart than it did with the 3-prong flash hider. Caution should be exercised by the weapon operator. This phenomenon is examined in further detail below. The at-ear waveform differences are extremely significant.
6.73.2.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 6-shot test of the SOCOM762-RC2 with the WARCOMP 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 with the SOCOM762-RC2 are shown in Figure 7a. A zoomed-in timescale is displayed in Figure 7b, in the region of peak sound pressure for Shot 1 and Shot 2. The real sound impulse (momentum transfer potential) histories at the ear from the same 6-shot test are shown in Figure 8. Again, full and short timescales are shown.
Figure 7a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle WARCOMP Ear Sound Pressure Signature
Figure 7b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle WARCOMP Ear Sound Pressure Signature, Short Time Window
Figure 8a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle WARCOMP Ear Sound Impulse Signature
Figure 8b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle WARCOMP Ear Sound Impulse Signature Peaks
The previously observed FRP characteristics measured at the muzzle are evident in the ear measurements. Note the significant magnitude of the peaks in both the pressure and impulse regimes. The peak pressure amplitude is 157.7 dB (Figure 7b); this waveform is a shock wave indicating direct gas venting from the mount area to the shooter’s head position.
PEW Science Research Note 8: As discussed in the previous SOCOM556-RC2 and SOCOM762-RC2 reviews with the WARCOMP, this behavior is highly irregular and atypical. This data is a direct empirical indication of silencer mount leakage on a centerfire rifle platform; a hazardous condition for the operator. PEW Science data and analysis indicates that this behavior occurs with the WARCOMP, independent of silencer model and weapon platform. The behavior is mount (WARCOMP) dependent. This level of direct blast propagation can result in direct impingement at the operator’s head position and can subject the operator’s face to high velocity particulate ejecta, independent of the host firearm, and is not related to semi-automatic or automatic weapon system operation. PEW Science recommends PPE be used for all suppressed weapon operation.
The impulse (Figure 8) is severe; note the relatively fast rise time from the direct shock wave at the ear position, after the gas exits the host weapon and enters the silencer (impulse peak at approximately 28.8 ms, Figure 8b). PEW Science recommends against the use of the WARCOMP mount with the SOCOM762-RC2 (or any Surefire silencers) on this platform due to potential operator hazard and potential mount debris and maintenance issues. Excessive combustion products entering the mount interface from the WARCOMP ports may result in premature mount seizing or binding.
Comparisons of the 3-prong flash hider and WARCOMP equipped systems are provided below.
6.73.3 SOCOM 3-Prong Flash Hider and WARCOMP Flash Hider Mount Comparison
Below, direct comparisons of the measured pressure and impulse waveforms with the two different mounts used in the two tests of the SOCOM762-RC2 are shown. 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!
Figure 9a and Figure 9b show first-shot muzzle overpressure and impulse comparisons, respectively. These comparisons directly illustrate the changes in gas dynamics at the muzzle due to WARCOMP mount leakage at the silencer-mount interface.
Fig 9a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signatures - Mount Comparison, FRP
Fig 9b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signatures - Mount Comparison, FRP
The 3-Prong Flash Hider is non-ported and equipped with “labyrinth seals;” these circumferential machined ridges on the mount help to prevent gasses from escaping the mount interface. PEW Science postulates that the porting is the most significant factor influencing the difference in muzzle blast pressure propagation from the mount interface. During the first shot, the flow rate of the SOCOM762-RC2 is so high that ancillary combustion from FRP masks some of the primary differences in gas dynamics between the use of the two mounts. After FRP, the difference is more easily discerned; Figure 10 displays comparisons of Shot 2.
Fig 10a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signatures - Mount Comparison, Shot 2
Fig 10b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signatures - Mount Comparison, Shot 2
Note that after the ancillary combustion ceases, subsequent shots display pure differences in gas dynamics during the use of different mounts. The WARCOMP leak occurs in early time (29.7 ms, Fig 10a); the leak is so severe that it delays gas propagation through the silencer and subsequent leaks coalesce with the delayed muzzle blast, continuing to build significant impulse until 30.7 ms (Fig 10b). The severe gas leak propagation from the WARCOMP results in greater impulse than from the 3-Prong during the entire positive phase.
The mount leakage phenomenon that occurs with the WARCOMP (but not with the 3-prong Flash Hider) was observed in the previous PEW Science testing and analysis of the Surefire SOCOM762-RC2 on a bolt-action rifle with both mount types and also during the PEW Science testing of the Surefire SOCOM556-RC2 on the MK18 with both mount types. When examining the results from the aforementioned four tests and the two subject tests, five primary variables are noted:
The silencer (SOCOM762-RC2 vs. SOCOM556-RC2)
The ammunition (7.62x51mm vs. 5.56x45mm)
The barrel length (20-in vs. 10.3-in)
The weapon operating mechanism (bolt-action rifle vs. automatic gas-operated rifle)
WARCOMP timing (the mount was simply installed on the bolt-action host weapon, whereas the mount was properly timed on the MK18 in all tests)
Despite the above five variables, the testing and analysis results are consistent. The silencers possess similar locking collars, the ammunition propellant combustion occurs with sufficient pressure to induce blast waves when released to atmosphere suddenly, the secondary blast waves from unburnt propellant from the shorter barrel only contribute further to the issue, the leakage happens in early time so weapon type is inconsequential, and finally, blast waves from the mount interface expand spherically, in three dimensions. Timing of the mount, even if it did influence blast propagation amplitude, would only do so negligibly in the free field.
The WARCOMP performance differential on the MK18 with the SOCOM762-RC2 is examined in further detail, below. The waveform differences at the shooter’s ear are extremely significant, just as they were with the SOCOM556-RC2 on the same weapon system.
Figure 11a and Figure 11b show first-shot shooter’s ear overpressure and impulse comparisons, respectively. These comparisons directly illustrate the extreme signature difference to the operator between use of the WARCOMP and the 3-prong flash hider equipped system. The differences are significant; the shockwave in Figure 10a from the WARCOMP represents an approximately 167% increase in overpressure at the shooter’s head position. Despite its short duration, it contributes to a significant early-time impulse event (Figure 11b).
Fig 11a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signatures - Mount Comparison, FRP
Fig 11b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signatures - Mount Comparison, FRP
At the shooter’s head position, the severity of WARCOMP use is immediately apparent during FRP. During subsequent shots, the trends continue (See Figure 12, below). The pressure waveforms occurring at approximately 26 ms (Fig 12a and 12b) are severe shock loads.
Fig 12a. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signatures - Mount Comparison, Shot 2
Fig 12b. SOCOM762-RC2 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signatures - Mount Comparison, Shot 2
Again, PEW Science does not recommend the use of the WARCOMP mount with the SOCOM762-RC2 or any Surefire silencer, on this platform, or any platform, for dedicated suppressed use. Other Surefire mounts, particularly those with the labrynth seals, exhibit measurably less hazardous performance for the weapon operator.
6.73.4 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 13 presents a comparison of the PEW Science Suppression Rating of the Surefire SOCOM762-RC2 with the 3-prong flash hider mount and the closed-tine WARCOMP mount to that of other 30 caliber silencers and 223 caliber rifle silences on the MK18 automatic AR15 rifle. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Figure 13. Suppression Rating Comparisons with the Surefire SOCOM762-RC2 and different Mounts, and other silencers, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis
From the above data, it can be concluded that the SOCOM762-RC2 suppressor has significantly higher sound suppression performance when used with the 3-prong flash hider mount, instead of the WARCOMP mount, at the shooter’s head position. Unlike during the use of the WARCOMP with the SOCOM556-RC2 on the MK18, the higher flow rate (lower back pressure) of the SOCOM762-RC2 results in a muzzle signature that is almost as severe with the gas leak as without; the SOCOM762-RC2 is significantly over-bored for the 5.56x45mm cartridge, and is designed for high flow rate, in general.
The extremely low at-ear Suppression Rating with the WARCOMP mount (regardless of silencer) is a function of the relatively high blast pressure originating from the mount interface leak and its proximity to the shooter’s ear; the MK18 possesses a 10.3-in barrel length. Note that the WARCOMP can also produce hazardous signature to the weapon operator on bolt action weapons, as was demonstrated in the testing and analysis of the Surefire SOCOM762-RC2 silencer in Review 6.26.
Note that the at-ear Suppression Rating is lower than the muzzle Suppression Rating with this particular silencer on the MK18 host weapon, regardless of mount.
It can also be concluded that the significant over-bore of the Surefire SOCOM762-RC2, and 30 caliber silencers in general, is detrimental to overall sound suppression performance on the MK18 weapon system. While the bore size significantly increases the flow rate (reduces the back pressure; reduces the PEW Science Omega Metric on the platform), it does so at the expense of signature severity to the shooter’s ear. The barrel length of the MK18 is short, and silencer’s flow rate so high, that the muzzle signature overwhelms the shooter. The signature to which the shooter’s ear is subjected is a function of both ejection port and muzzle signature. When the silencer’s endcap is in closer proximity to the shooter, the severity is increased. This phenomenon is observed in other over-bored silencers such as the Rugged Razor 762 (6.58) and the CGS Helios QD (Review 6.66). This phenomenon is less pronounced with the Q Trash Panda (6.61) due to the higher flow restriction (higher back pressure) of the Q Trash Panda on the MK18.
The coalescing of the ejection port overpressure with the primary muzzle blast exacerbates the severity of the signature at the shooter’s head position. It is not ejection port signature, alone, that dictates the signature measured at the shooter’s head position.
PEW Science Research Note 9: With the 3-prong flash hider, the SOCOM762-RC2 is unable to achieve the suppression performance of the 3-Prong equipped Surefire SOCOM556-RC2 (Review 6.52) on this platform. However, at the shooter’s head position, the hearing damage risk with the two silencers is comparable; this due to a net balance in signature severity; the back pressure of the SOCOM556-RC2 is high enough that the ejection port signature with that silencer induces similar signature severity as the significant muzzle signature from the SOCOM762-RC2 wrapping around the shooter’s head. This signature balance remains one of the most significant challenges of suppressing a short barrel rifle (SBR). To date, the most efficient balance shown in PEW Science testing and analysis is achieved from the HUXWRX OSS HX-QD 556 (6.54).
Although the WARCOMP’s gas leak effects are not immediately apparent in the muzzle Suppression Rating of the SOCOM762-RC2 when compared to that with the 3-Prong, this is only due to the silencer’s flow rate and its influence on muzzle signature. Relatively hazardous signature components at the shooter’s ear are still pervasive when using the WARCOMP, regardless of silencer or weapon platform.
6.73.5 Review Summary: SOCOM762-RC2 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-RC2 mounted with the SOCOM 3-Prong flash hider achieved a composite Suppression Rating™ of 24.9 in PEW Science testing. When mounted with the WARCOMP flash hider on the same host weapon and fired with the same ammunition, the SOCOM762-RC2 achieved a composite Suppression Rating of 22.8. As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Subjective Opinion:
The Surefire SOCOM762-RC2 is a full-size 30 caliber machine gun rated rifle silencer that possesses competitive sound signature suppression performance in the supersonic flow regime with 7.62x51mm cartridges, while also possessing significantly reduced back pressure. The performance of the SOCOM762-RC2 in short barrel 5.56x45mm applications is reduced.
The use of the Surefire locking collar is relatively straight forward. The SOCOM762-RC2 is compatible with the mounts for the SOCOM556-RC2, though its overall sound suppression performance on a short barrel 5.56x45mm weapon system is not comparable. The SOCOM762-RC2 is not only over-bored for the 5.56mm cartridge, but its flow rate is relatively high for a 30 caliber silencer. Both of these factors contribute significantly to its performance degradation on the MK18 when compared to the SOCOM556-RC2. Though the shooter may be subjected to similar hearing damage risk on this platform, the overall signatures differ.
Two mounts (the SOCOM 3-Prong Flash Hider and WARCOMP) were used in the testing of the SOCOM762-RC2 silencer, in the same test session. Previously, PEW Science tested the SOCOM556-RC2 silencer on the MK18 with both mounts and the SOCOM762-RC2 on a bolt action rifle with 7.62x51mm ammunition, with both mounts. Regardless of silencer, or platform, the testing and analysis results indicate that the use of the WARCOMP is unfavorable. The resulting gas leaks from the mount interface result in relatively high hazard to the weapon system operator.
Surefire advises that the WARCOMP mount 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 SOCOM 3-Prong Flash Hider with “labyrinth seals” and no porting offers significantly different suppressed performance than the WARCOMP with all Surefire rifle silencers. The seals are marketed by Surefire to prevent aft gas leakage at the mount interface. PEW Science data indicates that this claim is true, but the absence of ports is postulated to be a significant factor.
PEW Science highly recommends the use of a non-ported “labyrinth seal” equipped mount with the SOCOM762-RC2 (and with the SOCOM556-RC2) for the reasons stated in this review. It is possible that prolonged use of a ported WARCOMP with a silencer could result in higher sight or hearing risk to an operator if not properly equipped with the recommended PPE. Hearing and eye protection is recommended for the operation of suppressed small arms, in general. It is also possible that prolonged use of a ported WARCOMP mount may result in the need for more frequent mount maintenance intervals, as the silencer may seize or become “carbon-locked” to the mount more easily due to the combustion products venting through the WARCOMP ports. PEW Science highly recommends users of the Surefire mounting system clean their mounts regularly.
In this review, the SOCOM762-RC2 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.
