SSS.6.53 - SilencerCo Saker 556 and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle
/SilencerCo Saker 556 on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The Saker 556 was manufactured by SilencerCo. It is a 223 caliber centerfire rifle silencer, intended to suppress the 5.56x45mm NATO cartridge from barrels greater than or equal to 7 inches in length. It has a 1.5-inch diameter and is 6.4 inches long with the direct-thread Multiple Accessory Attachment Device (MAAD) mount. The silencer may also mount to the host firearm with other MAAD mounts or any other adapters possessing the SilencerCo Charlie rear thread pattern (1.375”-32tpi). The outer tube and end cap are constructed of heat treated stainless steel and the cast Stellite baffles are fully welded. As tested, the silencer weighs 17.8 ounces with the direct-thread mount installed. The Saker 556 is superseded by the Saker ASR, which can be obtained from Silencer Shop.
This Sound Signature Review contains single-test results using Saker 556 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 test. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Section 6.53.1 contains contains the Saker 556 test results and analysis.
Section 6.53.2 contains Suppression Rating comparisons of the Saker 556 with the Surefire SOCOM556-RC2 rifle silencer on the MK18.
Section 6.53.3 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 SilencerCo Saker 556 mounted with the direct-thread mount achieved a composite Suppression Rating™ of 32.6 in PEW Science testing. 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
6.53.1 Saker 556 Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the Saker 556 tested with the direct-thread mount 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. SilencerCo Saker 556 Sound Metric Summary
6.53.1.1 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 Saker 556 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 4a. In Figure 4b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shot 2.
Fig 1a. SilencerCo Saker 556 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature, 28-AUG-2021
Fig 1b. SilencerCo Saker 556 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature, 28-AUG-2021
Figure 2a. SilencerCo Saker 556 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature, 28-AUG-2021
Figure 2b. SilencerCo Saker 556 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature, 28-AUG-2021
Immediate differences in the the pressure and impulse waveforms shown in Figure 1 and Figure 2, respectively, are noted when compared to those from the Surefire SOCOM556-RC2 in Review 6.52. In addition to the significantly delayed gas jetting after the bullet exit event (Figure 1b), the initial rise to maximum peak positive phase impulse possesses a more gradual slope (Figure 2a). Both of these waveform differences indicate that the Saker 556 possesses a higher PEW Science Back Pressure Metric, Omega, than the SOCOM556-RC2. The Saker 556 has higher flow restriction (back pressure) than the SOCOM556-RC2. Omega metric data for the 5.56x45mm cartridge is the subject of ongoing PEW Science research. The measured first-round-pop (FRP) is visible in the impulse regime, in peak amplitude, timing, and wave shape, as is typical from a suppressed rifle. It should be noted that the FRP measured at the muzzle from the Saker556 is insignificant.
PEW Science Research Note 1: 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 75 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 2: 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 while the muzzle Suppression Rating of the Saker 556 is 32.4, the at-ear Suppression Rating is in a lower zone on the Suppression Rating Dose Chart. Caution should be exercised by the weapon operator.
6.53.1.2 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 on the left. A zoomed-in timescale is displayed on the right, in a sound pressure region of interest 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 4. Full and short timescales are shown.
Figure 3a. SilencerCo Saker 556 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, 28-AUG-2021
Figure 3b. SilencerCo Saker 556 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, Short Time Window, 28-AUG-2021
Figure 4a. SilencerCo Saker 556 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature, 28-AUG-2021
Figure 4b. SilencerCo Saker 556 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature Peaks, 28-AUG-2021
Similar to the measurements at the muzzle, the FRP from the Saker 556 at the shooter’s ear is not significant. However, what is significant, is the positive phase signature after primary muzzle blast, but before ground reflection (Figure 3b). This increase in gas momentum may be observed in the abnormally high late-time impulse waveforms beginning at approximately 35-ms in Figure 4a. This gas jetting, consisting of coalescing pressure waves from the late-time muzzle blast and primary ejection port pressure waves, is so intense that significant negative phase develops after its decay (45 ms, Figure 3b). These at-ear signature features are extreme and indicate the presence of significant gas flow momentum near the shooter’s head.
PEW Science Research Note 3: 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. The Saker 556 produces significant ejection port signature at the shooter’s head position with this weapon system. This is a direct result of its low flow rate (high back pressure).
Note that the at-ear Suppression Rating is in a low zone on the Suppression Rating Dose Chart. Caution should be exercised by the weapon operator.
6.53.2 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 5 presents a comparison of the PEW Science Suppression Rating of the SilencerCo Saker 556 to that of the Surefire SOCOM556-RC2 with two different mounts on the MK18 automatic AR15 rifle. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Figure 5. Suppression Rating Comparisons of the Saker 556 with the SOCOM556-RC2 , Using PEW-SOFT 5.56x45mm Supersonic Test Data
From the above data, it can be concluded that the SilencerCo Saker 556 has a more severe sound signature than the Surefire SOCOM556-RC2 to bystanders, and to the shooter, on this weapon platform. The louder signature of the Saker 556 occurs despite its higher flow restriction (higher back pressure). Furthermore, the higher back pressure of the Saker 556 results in a severe at-ear signature, lowering the Suppression Rating experienced by the weapon operator. There is no gas leak present from the Saker 556 on this platform. However, its back pressure is high enough that the at-ear Suppression Rating is significantly influenced. The low at-ear Suppression Rating is also function of the silencer’s proximity to the shooter’s ear; the MK18 possesses a 10.3-in barrel length. The coalescing of the ejection port overpressure with the primary muzzle blast exacerbates the severity of the signature at the shooter’s head position.
Note that the at-ear Suppression Rating is lower than the muzzle Suppression Rating with this particular silencer on the MK18 host weapon. The disparity in muzzle and ear Suppression Ratings is significant. Caution should be exercised by the weapon operator.
6.53.3 Review Summary: Saker 556 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 SilencerCo Saker 556 mounted with the direct-thread mount achieved a composite Suppression Rating™ of 32.6 in PEW Science testing. As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Subjective Opinion:
The SilencerCo Saker 556 is a full-size 5.56mm machine gun rated rifle silencer that possesses competitive sound signature suppression performance with many silencers on the market, while possessing significant flow restriction (back pressure) compared to some designs. Users should note that full-size 5.56mm rifle silencers are often smaller than their full-size 7.62mm (.30) counterparts.
The modular nature of the Saker MAAD mounting system is relatively straight forward. The newer Saker ASR series silencers supersede the original Saker model line. Differences between the original and updated Saker model lines largely consist of mount thread interface. The sound signature suppression differences between the two model lines are postulated to not be significant, but testing and analysis of the Saker ASR series is required to verify.
The Saker series is also offered in a 30-caliber (7.62mm) variant. All silencers in the series possess cast Stellite baffles. While extremely durable, the baffle design of the Saker consists of un-ported and notched curved cones, reminiscent of feature-reduced Omega baffles with no coaxial elements. The blast baffle of the Saker is cast differently; the so-called “Hoplon” geometric blast baffle shape prolongs resilience when subjected to significant muzzle blast from short barrel weapons by increasing the angle of incidence to the primary blast. The quantity of baffles, their geometry, and the bore aperture of the Saker 556, result in significant sound signature suppression at the muzzle, at the expense of high back pressure. The significant flow restriction, further exacerbated by lack of venting (porting) in the baffle stack, may result in significant ejection port signature at the shooter’s head position on many semiautomatic and automatic AR15 weapon systems. The ejection port signature with the Saker 556 on the MK18 weapon system is severe.
PEW Science highly recommends users exercise caution when fielding silencers with high flow restriction (high backpressure) on semiautomatic and automatic weapon systems. The weapon may unlock during its operating cycle prior to the occurrence of adequate pressure blowdown in the chamber and barrel, resulting in significant overpressure from the ejection port. This overpressure coalesces with the primary muzzle blast and exacerbates the severity of the signature at the shooter’s head position. This flow restriction may also result in abnormally high weapon cyclic rate. Host weapon tuning may be needed for reliable operation.
In this review, the Saker 556 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.
