SSS.6.144 - Surefire SOCOM556-MINI2 and the M4A1 Mid-Gas 5.56x45mm 14.5-in Barrel Automatic AR15 Rifle
/Surefire SOCOM556-MINI2 on the M4A1 Mid-Gas 5.56x45mm AR15 with 14.5-in Barrel
The SOCOM556-MINI2 is manufactured by Surefire. It is a 223 caliber centerfire rifle silencer, intended to suppress the 5.56x45mm NATO cartridge from barrels greater than or equal to 14.5 inches in length. It has a 1.5-inch diameter and is 5 inches long. 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 14 ounces and the 3-prong flash hider weighs 3.9 ounces, for a total system weight of 17.9 ounces, as tested. The SOCOM556-MINI2 can be obtained from Silencer Shop.
This review contains results from two separate tests. PEW Science tested the SOCOM556-MINI2 on the M4A1 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 SOCOM556-MINI2 system. Similar phenomena were measured and analyzed in previous testing as summarized in the following 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).
Cautions:
The WARCOMP mount increases postulated hazards in all tested regimes. Personal protective equipment (PPE), including eye and ear protection, is recommended for the operation of suppressed small arms, in general.
This is not 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 each weapon system may produce erroneous and potentially unconservative conclusions. Personnel hazards do not scale directly nor linearly between the two host weapon systems.
Both sets of test results in this Sound Signature Review are of the SOCOM556-MINI2 on the M4A1 Mid-Gas Automatic AR15 rifle, chambered in 5.56x45mm NATO with a 14.5-inch barrel. Federal XM193 55gr ammunition was used in the tests. The standard PEW Science M4A1 test host weapon system is described in Public Research Supplement 6.127.
Section 6.144.1 contains SOCOM556-MINI2 test results and analysis using the SOCOM 3-Prong flash hider mount.
Section 6.144.2 contains test results and analysis using the WARCOMP closed-tine flash hider mount.
Section 6.144.3 contains a detailed comparison of the sound signatures from the SOCOM556-MINI2 silencer on the M4A1 with both of the mount systems (Members Only).
Section 6.144.4 contains overall gross Suppression Rating comparisons of all tested systems.
Section 6.144.5 contains an article summary and PEW Science laboratory staff opinions.
Summary: When paired with the 14.5-in barrel M4A1 and fired with Federal XM193, the Surefire SOCOM556-MINI2 mounted with the SOCOM 3-Prong flash hider achieved a composite Suppression Rating™ of 29.2 in PEW Science testing. When mounted with the WARCOMP flash hider on the same host weapon and fired with the same ammunition, the SOCOM556-MINI2 achieved a composite Suppression Rating of 26.1.
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
6.144.1 SOCOM556-MINI2 Sound Signature Test Results (SOCOM 3-Prong Flash Hider)
A summary of the principal Silencer Sound Standard performance metrics of the Surefire SOCOM556-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 SOCOM556-MIN2 (3-Prong FH) Sound Metric Summary
6.144.1.1 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 SOCOM556-MINI2 with the 3-Prong Flash Hider are shown in Figure 1a. The sound signatures of Shot 1 and Shot 2 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 Shot 2 and Shot 3.
Fig 1a. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Sound Pressure Signature
Figure 2a. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature
The combustion gas propagation characteristics measured from the compact SOCOM556-MINI2 on the M4A1 weapon system are somewhat similar to that measured from the full size SOCOM556-RC2 on the same weapon system (6.128), albeit with some key differences:
Both silencers delay primary jetting until after the first coupled jet, with the SOCOM556-MINI2 signature scaled to a higher pressure amplitude (Fig. 1b).
Both silencers exhibit immediate FRP divergence causing increase gas momentum accumulation during the first shot, with the SOCOM556-MINI2 signature possessing a significantly higher rate increase (Fig. 2b).
Blowdown duration of the SOCOM556-MINI2 is reduced (Fig. 1a).
The SOCOM556-RC2 and SOCOM556-MINI2 pressure signatures both move into rarefaction relatively quickly, with the SOCOM556-MINI2 not possessing the prolonged impulse plateau exhibited by the full size version (ref. 6.128.1.1, Fig. 2b).
The above similarities and differences are a result of the SOCOM556-MINI2 being a truncated version of the SOCOM556-RC2, for all practical purposes. The same proximal venting adjacent to the first expansion chamber (blast chamber) in the RC2 is present in the MINI2. The six baffles in the MINI2, fewer than the 11 in the RC2, are of similar design. The overall length of the silencers differs by 1.4 inches (the MINI2 is almost 22% shorter than the RC2).
PEW Science Research Note 1: The early-time blast reflection environment inside the silencer, in close proximity to the muzzle orifice, does not appreciably change between the full size SOCOM556-RC2 and the SOCOM556-MINI2. As a result, latent effects on weapon function and kinematics are not significantly influenced from gas dynamics in that time regime. However, the late-time gas flow rate from the two systems does significantly differ; this difference is directly expressed in the rate at which maximum positive-phase impulse accumulation is reached 1.0 m left of the silencer’s end cap, which is the definition of the PEW Science Omega Metric research parameter (6.40), highlighted in (2), above. The aforementioned additional internal blast impulse accumulation from additive shock reflections has been defined by PEW Science as the alpha research parameter. The RC2 and MINI2 design iterations minimize a change in alpha while varying Omega. This results in the MINI2 having lower overall back pressure than the RC2, without significant semiautomatic weapon function changes, on some weapon systems. Users may note less “gas blow back” from the weapon breach when using a SOCOM556-MINI2, than they may notice with a SOCOM556-RC2, on the same weapon system. However, it is also possible that the difference may be negligible, depending on specific weapon system parameters. Regardless of this differential, the hazard to both shooters and bystanders is increased when fielding the MINI2 system on the M4A1 mid-gas platform, when compared to fielding the RC2 system. This increased hazard occurs despite decreased ejection port blast hazard from the MINI2, due to wave coalescence from the more severe muzzle blast. This is reflected in the detailed PEW Science Suppression Ratings at the beginning of this report and further examined in the shooter’s ear signature analysis in Sections 6.144.1.2 and 6.144.2.2 with the 3-Prong and WARCOMP mounts, respectively.
PEW Science Research Note 2: Unlike the negligible performance change with the SOCOM556-RC2 noted when transitioning from 10.3-in MK18 (6.52) to 14.5-in M4A1 combustion (6.128), PEW Science postulates that the SOCOM556-MINI2 would exhibit reduced performance on the MK18 weapon system, when compared to the 14.5-in M4A1 system examined in this report. This is due to the higher system flow rate.
PEW Science Research Note 3: The first-round-pop (FRP) signature of the SOCOM556-MINI2 silencer on the 14.5-in barrel M4A1, to bystanders, is relatively significant, relative to subsequent shots. This is a direct result of the silencer’s reduced baffle count, in this design.
PEW Science Research Note 4: 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 82 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 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 6: Note that the muzzle Suppression Rating of the SOCOM556-MINI2 with the 3-Prong mount is 28.0 and the at-ear Suppression Rating is 21.4; the same zone on the Suppression Rating Dose Chart. The lower back pressure of the SOCOM556-MINI2 compared with the SOCOM556-RC2 contributes to a less severe ejection port blast signature. However, the more severe muzzle blast from the MINI2 increases the overall severity of the signature to the shooter on the standard M4A1 weapon system. The WARCOMP mount may further increase this shooter hazard, as examined in Section 6.144.2.
The signatures measured at the shooter’s ear are presented below.
6.144.1.2 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 and 2. 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 short timescales are shown.
Figure 3a. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature
Figure 3b. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 4a. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature
Figure 4b. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature Peaks
As discussed in the preceding section, the SOCOM556-MINI2 exhibits faster blowdown and less net back pressure than the SOCOM556-RC2. Additionally, due to this higher gross flow rate, the contribution of ejection port blast load to the signature measured at the shooter’s head is reduced. The phenomenon is expressed in the above measured waveforms. Two features of note highlight the change, explicitly:
The expedient pressure amplitude decay in Figure 3b.
The front-loaded FRP impulse accumulation shown in Figure 4b.
PEW Science Research Note 7: For more detail regarding the front- and back-loaded FRP relative impulse accumulation phenomenon noted in (2), and its correlation with ejection port blast load signature dominance, please refer to section 6.111.3 in the Maxim Defense SURG evaluation report. The ejection port blast resulting from the use of the MINI2 on this weapon system is reduced when compared to the use of the full sized RC2. Nonetheless, the muzzle blast wave coalescence at the shooter’s head does increase the hazard to the weapon operator.
The SOCOM556-MINI2 presents 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. However, when using a ported WARCOMP flash hider, the system exhibits ancillary blast load propagation potential due to the Surefire mounting system possessing a relatively poor seal, which further increases shooter hazard. This phenomenon is examined in the test shown in Section 6.144.2, below.
6.144.2 SOCOM556-MIN2 Sound Signature Test Results (WARCOMP Flash Hider)
A summary of the principal Silencer Sound Standard performance metrics of the SOCOM556-MINI2 with the WARCOMP Closed-Tine 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 6.144.1, 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 SOCOM556-MIN2 (WARCOMP) Sound Metric Summary
6.144.2.1 SOUND SIGNATURES AT THE MUZZLE
Real sound pressure histories from a 6-shot test acquired with PEW-SOFT™ are shown below. 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 SOCOM556-RC2 with the WARCOMP Closed-Tine Flash Hider are shown in Figure 5a. The sound signatures of Shot 1 and Shot 2 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, Shot 3, and Shot 4.
Fig 5a. Surefire SOCOM556-MIN2 (WARCOMP) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Pressure Signature
Fig 5b. Surefire SOCOM556-MIN2 (WARCOMP) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Pressure Signature, Short Time Window
Fig 6a. Surefire SOCOM556-MIN2 (WARCOMP) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature
Fig 6b. Surefire SOCOM556-MIN2 (WARCOMP) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature, Short Time Window
Just as was noted in PEW Science testing of the SOCOM762-RC2 on a 20-in barrel .308 bolt-action rifle with the WARCOMP mount (6.26), the testing of the SOCOM556-RC2 on a 10.3-in barrel 5.56mm MK18 with the WARCOMP mount (6.52), and the testing of the SOCOM556-RC2 on the M4A1 with the WARCOMP mount (6.128), the M4A1 testing of the Surefire SOCOM556-MINI2 with the WARCOMP mount displays more severe gas momentum accumulation due to a leak out of the mount-collar interface, than it does with the 3-Prong flash hider. This is visible in both pressure space (Figure 5) and impulse space (Figure 6).
PEW Science Research Note 8: The Surefire SOCOM silencer mount interface possesses a taper that does not enact a complete gas seal. Machined circumferential recesses on some mounts (the so-called “labrynth seals”) create turbulence that disrupt gas flow and may reduce the rate of high pressure gas propagation to atmosphere at the mount interface. The WARCOMP family of mounts, regardless of the presence of these machined recesses, possess drilled ports that direct thrust forces in the unsuppressed state to counteract unfavorable recoil forces. When suppressed, the WARCOMP mount ports direct a significant amount of high pressure gas flow to the mount interface and the lack of adequate seal in the SOCOM silencer mount system results in significant blast load propagation to atmosphere. The blast load from the mount leak propagates in addition to the blast load originating from the end cap of the silencer. The two loads are superimposed at approximately 29.7 ms in Figure 5b. The relatively fast rise-times of the blast loads are indicative of shocks, further indicating a sudden release of high pressure gas to atmosphere, and is consistent with all Surefire suppressed WARCOMP mount silencer test results conducted by the PEW Science laboratory, to date.
PEW Science Research Note 9: The SOCOM556-MINI2 generates an FRP signature with the WARCOMP mount that is particularly high amplitude with prolonged positive phase (ref. Figure 5b and Figure 6b). The higher amplitude impulse accumulation, with longer duration positive phase, results from the additive effects of the more severe muzzle blast from the MINI2, coupled with the WARCOMP mount leak.
Due to the reduced leak severity of the M4A1 system, along with a greater standoff distance between the mount interface and the weapon operator, hazards to the operator with the WARCOMP mount with the MINI2 are reduced on the M4A1, when compared to that of the RC2 with the WARCOMP mount the MK18. This differential can be examined using the PEW Science Rankings Table in Section 7 of the Standard. Section 6.144.4 of this report only contains M4A1 comparison data. The SOCOM556-MINI2 is not intended for, nor has it been tested by PEW Science on, the 10.3-in barrel MK18 weapon system.
More detailed comparisons between 3-Prong Flash Hider mount and WARCOMP Closed-Tine Flash Hider mount performance on the 14.5-in M4A1 midgas weapon system are provided in Section 6.144.3.
The signatures measured at the shooter’s ear are presented below.
6.144.2.2 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 with the SOCOM556-MINI2 with the WARCOMP Closed-Tine Flash Hider are shown in Figure 7a. A zoomed-in timescale is displayed in Figure 7b, in the region of peak sound pressure. The real sound impulse (momentum transfer potential) histories at the ear from the same 6-shot test are shown in Figure 8.
Fig 7a. Surefire SOCOM556-MIN2 (WARCOMP) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature
Fig 7b. Surefire SOCOM556-MIN2 (WARCOMP) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Fig 8a. Surefire SOCOM556-MIN2 (WARCOMP) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature
Fig 8b. Surefire SOCOM556-MIN2 (WARCOMP) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature, Short Time Window
As demonstrated in all WARCOMP tests in the Standard, the operator is most vulnerable to the increased hazards from WARCOMP mount leaks. As previously observed in 7.62mm bolt-gun WARCOMP testing and all 5.56mm WARCOMP testing, there are again significant additive blast loads displayed in both the pressure and impulse regimes in this MINI2 M4A1 test. There are blast load shock waves at approximately 29.8 ms (Figure 7b) occurring prior to primary muzzle blast, indicating direct gas venting from the mount area to the shooter’s head position. This gas momentum accumulates at the head as shown in Figure 8.
PEW Science Research Note 10: As discussed in the previous SOCOM762-RC2 and SOCOM556-RC2 test reports with the WARCOMP, this behavior is highly irregular and atypical. This data with the SOCOM556-MINI2 is, again, 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 reflection 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.
It is interesting to note that the front-loaded FRP impulse accumulation is maintained when transitioning from 3-Prong use to WARCOMP use with the MINI2. This again highlights the fact that the MINI2 still reduces ejection port blast hazard to the weapon operator on this host, when compared with the RC2, even if mounted with a WARCOMP. Nonetheless, the shooter’s ear hazard in this configuration is significant. The Suppression Rating at the shooter’s ear is 17.2 with a WARCOMP-equipped MINI2, which is more hazardous than experienced with the RC2, due to the coalescence of more severe muzzle blast. The reader may compare the back-loaded FRP muzzle blast in Figure 8b, above, with that of the same phenomenon in Figure 8b in 6.128.1.2.2. Note the higher amplitude and longer duration of the accumulation with the MINI2.
PEW Science Research Note 11: On the M4A1 weapon system, the muzzle sound signature of the SOCOM556-RC2 was more severe when using the WARCOMP mount than the 3-Prong mount, despite the peak pressure amplitude from the WARCOMP mount being lower. Note that in this test of the MINI2, the average peak blast pressure measured at the shooter’s ear in the WARCOMP test is only 0.6 dB greater than that measured in the 3-Prong test. The hazard, in both cases, is still significantly different. This is because it is not only peak pressure amplitude that dictates blast hazard; it is also blast wave shape, phase, and duration. Direct, detailed performance comparisons of the WARCOMP and 3-Prong Flash Hider with the SOCOM556-MINI2 are provided in Section 6.144.3, below.
6.144.3 SOCOM556-MINI2 Detailed Mount Performance Comparisons
Below, direct comparisons of the measured pressure and impulse waveforms with the two different mounts used in two tests of the SOCOM556-MINI2 are shown. This is a 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!
6.144.3.1 Muzzle Signature Variations with Mount
Figure 9a and Figure 9b show first and second shot muzzle overpressure and impulse comparisons, respectively, of the two mount tests. These comparisons directly illustrate the similarities and differences in gas dynamics at the muzzle due to the high pressure gas leak from the WARCOMP mount, compared to use of the 3-Prong Flash Hider.
Fig 9a. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO FRP Muzzle Pressure Mount Comparison
Fig 9b. Surefire SOCOM556-MIN2 (3-Prong FH) 5.56x45mm NATO FRP Muzzle Impulse Mount Comparison
With the 3-Prong mount, the coupled jet and bullet shock occurring in early time (Fig. 9a) immediately give way to a suppressed lower amplitude wave propagation. As the WARCOMP mount leaks, the muzzle blast immediately coalesces with the coupled jet and a substantial shockwave profile is formed. The 3-Prong pressure history moves into the negative phase more quickly, whereas the WARCOMP blast pressure continues to build momentum for a longer duration. This energy from additional muzzle blast is expressed as additional and longer duration momentum transfer potential in impulse-space in Figure 9b.
PEW Science Research Note 12: The WARCOMP not only allows higher amplitude blast pressure to propagate; it does so for a longer duration, with higher gas momentum. This occurs because the leak is present immediately adjacent to the muzzle, near the first expansion (blast) chamber. The combustion gasses are undergoing initial expansion immediately after bullet uncorking, and contain the most energy at this initial external origin. Muzzle blast originating from the silencer’s end cap does not build such momentum, as the combustion gasses have been expanded and cooled significantly, in comparison.
6.144.3.2 Shooter’s Ear Signature Variations with Mount
As previously discussed, the Surefire SOCOM silencer mount interface possesses a taper that does not enact a complete gas seal. Machined circumferential recesses on the 3-Prong mount (the so-called “labrynth seals”) create turbulence that disrupt gas flow and may reduce the rate of high pressure gas propagation to atmosphere at the mount interface. The WARCOMP family of mounts, regardless of the presence of these machined recesses, possess drilled ports that direct thrust forces in the unsuppressed state to counteract unfavorable recoil forces. It is these ports that are the most significant factor influencing the difference in muzzle blast pressure propagation from the mount interface when using the 3-Prong mount or a WARCOMP mount with a silencer.
The mount leakage phenomenon that occurs with the WARCOMP is observed in all previous PEW Science testing and analysis of Surefire rifle silencers.
Despite the different weapons, cartridges, and barrel lengths, 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 shorter barrels 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.
The 3D spherical expansion of the WARCOMP blast load leak is directly measurable at the operator’s head with the SOCOM556-MINI2, as it is in all other cases.
Figure 10a and Figure 10b show first-shot shooter’s ear blast pressure and blast impulse comparisons, respectively. These comparisons directly illustrate the signature difference to the operator between use of the WARCOMP and the 3-prong flash hider equipped system, on the 14.5-in barrel M4A1 midgas host weapon.
Fig 10a. Surefire SOCOM556-MIN2 5.56x45mm NATO FRP Ear Pressure Mount Comparison
Fig 10b. Surefire SOCOM556-MINI2 5.56x45mm NATO FRP Ear Impulse Mount Comparison
The same WARCOMP leak shock load measured 1.0 m left of the end cap displayed in Figure 9a, nested with end cap muzzle blast, propagates rearward toward the shooter’s head and is displayed in Figure 10a, decoupled from the end cap muzzle blast. The blast load is decoupled in this case because its time of arrival happens more quickly due to its origin (the silencer mount) being in closer proximity to the shooter’s head than the silencer’s end cap. Therefore, the shock load displayed in Figure 10a is the pure mount leak, with no other blast wave coalescence. Note that the rise time is slightly longer than a pure shock (though it is still a supersonic shock phenomenon). This slightly reduced rise time is most likely due to the orifice obstruction of the mount interface.
The added energy from the early-time WARCOMP blast load leak is expressed in impulse space at approximately 29 ms in Figure 10b. The added positive phase energy from the persistent leak, and its coalescence with end cap muzzle blast, maintains a higher positive phase impulse amplitude for much of the accumulation history. The impulse curve comparisons highlight how ejection port blast, WARCOMP leak blast, and end cap blast, all combine to increase shooter’s ear hazard. The WARCOMP leak is not the only hazard; it is a tertiary source of blast load hazard to the weapon operator on this weapon system. All blast loads have discrete origins with additive terminal effects.
Gross hazards and behaviors with the M4A1 weapon system are compared in the following section.
6.144.4 Suppression Rating Comparison (5.56x45mm from the M4A1)
Figure 11 presents a comparison of the PEW Science Suppression Rating of the Surefire SOCOM556-MIN2 and SOCOM556-RC2 with both the 3-Prong Flash Hider and WARCOMP Closed-Tine Flash Hider mounts with that of the CAT WB on the M4A1 weapon system. The standard PEW Science M4A1 test host weapon system is described in Public Research Supplement 6.127. As PEW Science research with the M4A1 system continues, the dataset will be further populated.
Figure 11. Suppression Rating Comparisons of the Surefire SOCOM556-MIN2 and SOCOM556-RC2 with different mounts and the CAT WB, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis
Figure 11 presents an overall summary of the postulated hazards to the operator and bystanders when fielding a Surefire SOCOM556-MINI2 on the M4A1 weapon system with two different muzzle devices. Data is also presented for the fielding case of the Surefire SOCOM556-RC2 (6.128) on the same muzzle devices, along with fielding of the CAT WB (6.130). 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 SOCOM556-MINI2 with the 3-Prong flash hider provides comparable hazard reduction to the weapon operator as the SOCOM556-RC2 with a WARCOMP mount, on this weapon system in the free field.
Use of the WARCOMP mount with the MINI2 is significantly more hazardous to the weapon operator than other configurations on the M4A1, though not as hazardous as use of the WARCOMP mount with the RC2 on the MK18 (ref. 6.52).
The WARCOMP increases hazards to both the shooter and to bystanders, regardless of silencer. However, the hazard to the shooter is inversely proportional to the standoff between the mount interface and the shooter’s head; the increase in operator hazard from a suppressed WARCOMP is more pronounced on shorter-barrel weapons. This is expected.
The performance gap between the two extremes of suppressed systems displayed in the current M4A1 dataset is significant; the difference in signature severity produced by the CAT WB on this weapon system, compared with that of a WARCOMP-equipped SOCOM556-MINI2, is pronounced.
Increased gross flow rate (lower back pressure) does pay dividends in ejection port blast hazard reduction to the 14.5-in barrel M4A1 midgas weapon operator, but an accompanying increased severity of suppressed muzzle blast may negate the benefit to the operator. The MINI2 still produces greater hazard to the operator than the RC2 on this weapon system, despite its lower back pressure.
As detailed in this report, the Suppression Rating at the shooter’s ear may be significantly influenced by the ejection port signature from an AR15; all other things equal. For details on performance increases that are possible when “tuning” an AR-15 weapon system for a silencer, please see Review 6.111. It is important to note that not all silencers will possess a significant increase in shooter’s ear Suppression Rating from weapon tuning. 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.
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.
6.144.5 Review Summary: Surefire SOCOM556-MIN2 on the M4A1 Mid-Gas 5.56x45mm AR15 with 14.5-in Barrel
When paired with the 14.5-in barrel M4A1 and fired with Federal XM193, the Surefire SOCOM556-MINI2 mounted with the SOCOM 3-Prong flash hider achieved a composite Suppression Rating™ of 29.2 in PEW Science testing. When mounted with the WARCOMP flash hider on the same host weapon and fired with the same ammunition, the SOCOM556-MINI2 achieved a composite Suppression Rating of 26.1.
As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Laboratory Staff Opinion:
The Surefire SOCOM556-MINI2 is a compact 5.56mm rifle silencer that possesses competitive sound signature suppression performance for its size, while possessing reduced back pressure compared to some designs. Users should note that the MINI2 is only 5 inches long and its suppression performance does not reach the levels of some larger designs. The SOCOM556-MINI2 is intended for use on 5.56x45mm weapons with barrels 14.5-in and longer.
Two mounts (the SOCOM 3-Prong Flash Hider and WARCOMP) were used in the testing of the SOCOM556-MINI2 silencer on the M4A1 rifle. Previously, PEW Science has tested a variety of Surefire silencers on multiple weapon systems and cartridges with both mounts. Testing and analysis results indicate that the use of the WARCOMP is unfavorable for hazard reduction when compared with the 3-Prong Flash Hider mount, regardless of cartridge, barrel length, and silencer.
In this test program, it was concluded that the Surefire SOCOM556-MINI2 with the 3-Prong flash hider provides comparable hazard reduction to the weapon operator as the SOCOM556-RC2 with a WARCOMP mount, on this weapon system in the free field. Use of the WARCOMP mount with the MINI2 is significantly more hazardous to the weapon operator than other configurations on the M4A1, though not as hazardous as the use of the WARCOMP mount with the RC2 on the MK18.
It should be noted that the WARCOMP increases hazards to both the shooter and to bystanders, regardless of silencer. However, the hazard to the shooter is inversely proportional to the standoff between the mount interface and the shooter’s head; the increase in operator hazard from a suppressed WARCOMP is more pronounced on shorter-barrel weapons. This is expected. As previously discussed, the Surefire SOCOM silencer mount interface possesses a taper that does not enact a complete gas seal. Machined circumferential recesses on the 3-Prong mount (the so-called “labyrinth seals”) create turbulence that disrupt gas flow and may reduce the rate of high pressure gas propagation to atmosphere at the mount interface. The WARCOMP family of mounts, regardless of the presence of these machined recesses, possess drilled ports that direct thrust forces in the unsuppressed state to counteract unfavorable recoil forces. It is these ports that are the most significant factor influencing the difference in muzzle blast pressure propagation from the mount interface when using the 3-Prong mount or a WARCOMP mount with a silencer.
The performance gap between the two extremes of suppressed systems displayed in the current M4A1 dataset is significant; the difference in signature severity produced by the CAT WB on this weapon system, compared with that of a WARCOMP-equipped SOCOM556-MINI2, is pronounced. Increased gross flow rate (lower back pressure) does pay dividends in ejection port blast hazard reduction to the 14.5-in barrel M4A1 midgas weapon operator, but an accompanying increased severity of suppressed muzzle blast may negate the benefit to the operator. The MINI2 still produces greater hazard to the operator than the RC2 on this weapon system, despite its lower back pressure.
In this review, the Surefire SOCOM556-MINI2 performance metrics depend upon suppressing a supersonic centerfire rifle cartridge on a commonly fielded 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.
