SSS.6.92 - Dead Air Sandman-S and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle
/Dead Air Sandman-S on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The Sandman-S is designed by Dead Air. It is a 30 caliber centerfire rifle silencer, intended to suppress most cartridges with projectiles appropriately sized to travel through the bore, up to and including 300 Winchester Magnum. It has a 1.5-inch diameter and is 6.8 inches in length with the included flat end cap. Multiple end cap options are available for use with the Sandman-S. The user may also choose from various Dead Air KeyMo muzzle devices on which to mount the silencer to the host weapon with its welded proprietary mount. The outer tube and mount are stainless steel and the cast Stellite baffles of the inner core are fully-welded. The silencer weighs 21.7 ounces with the 3-prong KeyMo flash hider. The Sandman-S can be obtained from Silencer Shop.
This Sound Signature Review contains single-test results using the Dead Air Sandman-S with the 3-prong KeyMo flash hider mount 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 6.92.1 contains the Sandman-S test results and analysis.
Section 6.92.2 contains Suppression Rating comparisons of the Sandman-S with dedicated 223 and 30 caliber silencers on the current market, including the HUXWRX FLOW 556k, Energetic Armament ARX, KAC QDSS-NT4, Rugged Razor556, Otter Creek Labs Polonium, Surefire SOCOM556-RC2, HUXWRX HX-QD 556 and HX-QD 556k, Q Trash Panda, CGS Helios QD, SilencerCo Saker 556, Rugged Razor762, and others.
Section 6.92.3 contains the review summary and PEW Science subjective opinions.
Note that PEW Science Member Research Supplement 6.93 contains an analysis of the Dead Air Sandman-S using the 5.56 mm end cap on the MK18 and compares its performance using the standard 30 caliber endcap.
Summary: When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Dead Air Sandman-S mounted with the 3-prong KeyMo flash hider mount achieved a composite Suppression Rating™ of 24.9 in PEW Science testing. As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
The supersonic .308 performance of the Dead Air Sandman-S is detailed in previous Sound Signature Review 6.11, in which it achieved a Suppression Rating of 32.6.
Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings
6.92.1 Dead Air Sandman-S Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the Sandman-S tested with the 3-prong KeyMo flash hider 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. Dead Air Sandman-S Sound Metric Summary
6.92.1.1 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 Sandman-S 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 Shots 1 through 4.
Fig 1a. Dead Air Sandman-S 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. Dead Air Sandman-S 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature
Figure 2a. Dead Air Sandman-S 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. Dead Air Sandman-S 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
The Dead Air Sandman-S is a 30 caliber rifle silencer and was previously evaluated on a .308 bolt-action rifle in Sound Signature Review 6.11. The propensity for the Sandman-S to exhibit relatively high flow rate or low back pressure with the 7.62x51mm NATO cartridge was highlighted upon the examination of its Omega Metric (Omega_762, Public Research Supplement 6.40). As stated, the Omega Metric correlates with flow restriction for a given cartridge. When over-bored silencers are used on weapon systems, such as the Sandman-S on the 5.56x45mm MK18, relative flow restriction can change.
PEW Science Research Note 1: An excellent example of a change in relative behavior across weapon systems for an over-bored silencer is the comparison of the Dead Air Sandman-S with the Rugged Razor762 on the MK18 (Review 6.58). The Razor762 is shorter than the Sandman-S, and its baffles are more restrictive, though they are less numerous. On a 20-in .308 bolt-action host weapon, the Razor762 possesses nominally higher flow restriction than the Sandman-S. This is reflected in its Omega_762 metric. However, when placing the two silencers on the 5.56x45mm MK18, the Razor762 is unable to trap gas as efficiently, and its flow rate nominally increases over that of the Sandman-S. The holistic signature differences between the two silencers on the MK18 are presented in Section 6.92.2 of this review.
PEW Science Research Note 2: The nominally increased flow restriction with the Dead Air Sandman-S is also reflected in the muzzle signatures (Figure 1), in which there is clear decoupling between the first muzzle jet events and the first major jetting which builds from approximately 30 ms (Figure 1b). Despite this consistent early-time flow shaping, the Sandman-S produces a common artifact of primary axial over-bore for the cartridge, in later-time impulse accumulation. Figure 2 displays these irregularities as the shot string continues. Shot 2 and Shot 3 are suppressed after FRP, as typical. After Shot 3, the Sandman-S signature becomes erratic; the over-bored baffle stack being unable to contain the secondary combustion and excess propellant burning from the 10.3-in MK18 rifle. Similar behavior on the MK18 is noted with the Energetic Armament ARX (Review 6.82), the aforementioned Rugged Razor762, and the Q Trash Panda (Review 6.61). Over-bored silencers that do not exhibit these inconsistencies include silencers like the Surefire SOCOM762-RC2 (Review 6.73) and CGS Helios QD (Review 6.66). Both the Surefire and CGS silencers have significantly more advanced flow geometry than the aforementioned silencers and are less overwhelmed by the high pressure jetting from the 10.3-in MK18. Primary axial over-bore, without additional flow paths, consistently demonstrates erratic impulse accumulation in PEW Science MK18 testing.
The flow rate of the Dead Air Sandman-S, like most over-bored silencers, is higher than that of dedicated silencers for the cartridge. For example, the Otter Creek Labs Polonium (Review 6.75), Surefire SOCOM556-RC2 (Review 6.52), SilencerCo Saker 556 (Review 6.53), and KAC QDSS-NT4 (Review 6.78) all possess lower flow rate (higher back pressure) than the Dead Air Sandman-S on the MK18 weapon system.
PEW Science Research Note 3: It should be noted that although the Dead Air Sandman-S is a 30 caliber rifle silencer, it produces significantly higher back pressure on the MK18 than silencers exhibiting very high flow rates, such as the OSS HX-QD 556 (Review 6.54), OSS HX-QD 556k (Review 6.64), and the HUXWRX FLOW 556K (Review 6.83).
Interestingly, the Dead Air Sandman-S exhibits extremely similar holistic performance to the Rugged Razor556 (Review 6.76) on the MK18. By removing a baffle from the Razor762 to form the Razor556, the expansion volume and baffle design produces almost identical signatures to the Sandman-S on this weapon system, with regard to hearing damage potential and gross gas dynamics. The Surefire SOCOM762-RC2 is also extremely similar is gross signature severity to these two silencers on the MK18, albeit in a more consistent fashion. The three silencers each possess drastically different design elements, are different lengths, and achieve similar sound signature suppression, overall. The silencers differ in their signature consistency.
PEW Science Research Note 4: The Dead Air Sandman-S exhibits significant first round pop (FRP) to bystanders, in that the severity of hearing damage risk to bystanders is postulated to be significantly higher during the first shot with the Sandman-S than with subsequent shots, in accordance with PEW Science inner ear modeling. The ancillary combustion during Shot 1 is observed in both pressure space (Figure 1b) and impulse space (Figure 2a).
PEW Science Research Note 5: As in all semiautomatic AR15 weapon testing, a second pressure pulse originates from the ejection-port signature of the weapon and it occurs early enough in time such that its waves coalesce with that of the muzzle signature. However, in late time (at approximately 80 ms in Figure 1a) the mechanical noise of the bolt closing is observed. The pressure signature of Shot 6 does not display this event due to the bolt remaining open after the sixth and final round is fired from the magazine.
PEW Science Research Note 6: The closing time of the 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, until the aforementioned late-time irregularities resulting from primary axial over-bore.
As typically indicated, first-round sound signatures always differ from subsequent shots, as the atmosphere within the silencer changes. The FRP phenomenon cannot always be shown by viewing only the peak sound pressure. This is one of the reasons why The Silencer Sound Standard requires examining multiple sound signature metrics. Ammunition consistency can play a role in the determination of FRP, however, the close examination of measured pressure and impulse waveforms typically excludes ammunition from the possible factors influencing true FRP, due to the relative consistency of most high quality factory ammunition.
PEW Science Research Note 7: Note that the muzzle Suppression Rating of the Dead Air Sandman-S with the flash hider mount is 22.0 and the shooter’s-ear Suppression Rating is 20.8; the same zone on the Suppression Rating Dose Chart. The Sandman-S produces a relatively severe overall signature on the standard MK18 weapon system; its high flow rate 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 5.56 mm end cap changes the gas dynamics, and thus the suppression performance, of the Sandman-S on this platform. This phenomenon is explored in PEW Science Member Research Supplement 6.93.
The signatures measured at the shooter’s ear are presented below.
6.92.1.2 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. A zoomed-in timescale is displayed in Figure 3b, 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 4. Again, full and short timescales are shown.
Figure 3a. Dead Air Sandman-S 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature
Figure 3b. Dead Air Sandman-S 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 4a. Dead Air Sandman-S 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature
Figure 4b. Dead Air Sandman-S 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature Peaks
Unlike in the measurements at the muzzle, the FRP from the Sandman-S at the shooter’s ear is less severe and less noticeable on this weapon system.
PEW Science Research Note 8: The severe FRP of the Dead Air Sandman-S at the muzzle on the MK18 begins to be apparent in the shooter’s ear signatures, starting with a nontrivial pressure divergence at approximately 28.75 ms in Figure 3b. The secondary impulse accumulation continuing until 30.8 ms in Figure 4 is further evidence of this. It is not until later shots that impulse accumulation in late time is noted after FRP, though it is due to a different phenomenon:
As highlighted in Figure 4a, the overall impulse at the shooter’s ear is erratic in later shots, similar to that measured at the muzzle. These waveform indicators measured at the ear are consistent with erratic secondary combustion due to its significant over-bore for the MK18.
The erratic nature of the gas flow and its duration components also negatively influence the impact on the human inner ear. For example, the Sandman-S is measured to possess lower peak impulse than the HUXWRX FLOW 556k at the shooter’s ear, on the same platform, but it also exhibits a lower Suppression Rating (the Sandman-S is more damaging to the ear; it is objectively louder on the platform). The Suppression Rating is a holistic sound signature metric that takes into account not only signature amplitude, but duration, timing, phase, and frequency components of the sound signature. The Rating is an indicator of inner ear response which directly correlates with hearing damage potential.
Like with other silencers utilizing primary axial over-bore for a given cartridge on a weapon system, the erratic combustion behavior in Figure 4 may be uncharacteristic of the Sandman-S with 5.56x45mm use through longer barrels. Without secondary burning, the bore aperture and baffle geometry may produce more normalized flow, as measured in its .308 bolt-action rifle in Sound Signature Review 6.11. This type of flow normalization (use of the Sandman-S on longer barrel 5.56x45mm host weapons) is postulated to increase the Suppression Rating in conjunction with the increase in distance of muzzle pressure source to the shooter’s ear.
Holistic suppression performance comparisons on the MK18 weapon system are examined in the section below.
6.92.2 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 5 presents a comparison of the PEW Science Suppression Rating of the Dead Air Sandman-S with the 3-prong KeyMo flash hider mount to that of other 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 5. Suppression Rating Comparisons of the Dead Air Sandman-S 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 Dead Air Sandman-S performs extremely similarly in sound signature suppression to some other 30 caliber silencers on the MK18. For example, the Sandman-S and Surefire SOCOM762-RC2 (Review 6.73) exhibit the same Composite Suppression Rating on the weapon system, and only slightly differ in muzzle and shooter’s ear signatures. Interestingly, the Dead Air Sandman-S also exhibits extremely similar holistic performance to the Rugged Razor556 (Review 6.76) on the MK18. By removing a baffle from the Razor762 to form the Razor556, the expansion volume and baffle design produces almost identical signatures to the Sandman-S on this weapon system, with regard to hearing damage potential and gross gas dynamics. These three silencers each possess drastically different design elements, are different lengths, but achieve similar sound signature suppression on the MK18, overall. The silencers differ in their signature consistency. Whereas the Sandman-S and Razor556 have relatively simple baffle geometries, the SOCOM762-RC2 possesses more complex vent paths. The flow rates of the silencers are similar on the weapon system, and advanced venting of the RC2 series results in more efficient gas dynamics.
Another interesting comparison is that on the MK18, the Dead Air Sandman-S produces a signature that is extremely similar in severity to that of the vented end cap configuration of the CGS Helios QD (Review 6.66). Given the extremely high flow rate of the Helios QD in that configuration, the Sandman-S having the same signature severity at the muzzle, with higher back pressure, demonstrates its relatively inefficient suppression performance on this platform. In the context of the holistic Silencer Sound Standard pedigree, to date, the data and analysis indicates that the Dead Air Sandman-S is more efficient at balancing flow rate and sound suppression on a conventional length 7.62x51mm weapon system than it is on a short barrel 5.56x45mm weapon system.
Several rifle silencers are marketed as possessing increased flow rate or “low back pressure.” The method by which flow rate is increased, and back pressure reduced, is paramount to overall performance. The Silencer Sound Standard illustrates numerous examples of high flow rate achieved through primary axial over-bore resulting in significant performance detriment in suppressing the MK18 automatic short barrel rifle. The Standard also illustrates some examples of primary axial over-bore resulting in performance compromise, but with favorable complimentary design features resulting in more balanced performance. Significant sound suppression performance dividends are often noted when silencers use dedicated bores, and these performance increases are also possible with supplementary venting. The difference between primary axial over-bore and complex additional flow path venting, in silencer performance, is significant.
PEW Science research indicates that sound signature suppression optimization for the short-barrel automatic 5.56x45mm AR15 platform is best achieved through one or more of the following primary mechanisms:
Silencer over-bore.
Baffle stack venting arrays.
Annular venting.
Continuous venting (lengthened flow path geometry).
The above four mechanisms of optimizing silencer sound suppression, and flow rate, are continued subjects of PEW Science internal research.
It is important to note that 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. 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.
Bystanders may perceive the Dead Air Sandman-S to be louder than many silencers shown in Figure 5 when fired on the MK18 host weapon. Personnel firing the weapon may experience hearing damage risk on par with that from using the vented CGS Helios QD, the Surefire SOCOM762-RC2 with its 3-prong mount, or the Rugged Razor556. It is important to note that the signature from the Dead Air Sandman-S will change when using the 5.56 mm end cap instead of the standard 30 caliber end cap. This phenomenon is explored in PEW Science Member Research Supplement 6.93.
6.92.3 Review Summary: Dead Air Sandman-S 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 Dead Air Sandman-S mounted with the 3-prong KeyMo flash hider mount achieved a composite Suppression Rating™ of 24.9 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 Dead Air Sandman-S is a compact 30 caliber machine gun rated rifle silencer that possesses moderate sound signature suppression performance with moderate back pressure on 5.56x45mm host weapons. When compared to dedicated 5.56 mm silencers, it should be considered full-size or large. The silencer is advertised to have extreme durability and is one of the heavier silencers on the market for its size, at a total system weight of 21.7 ounces, as tested.
The Sandman-S uses an iteration of a feature-reduced and modified stepped-cone baffle, similar to the feature-reduced curved-cone baffle used in the Omega 300 from SilencerCo and other companies, with the primary difference being an enlarged center orifice to facilitate higher axial gas flow rate. The influence of the larger center orifice on rise-time to peak impulse is more evident on 7.62x51mm weapons with the Sandman-S, as the expansion volume configuration of its baffle stack produces a less efficient combination of flow rate and sound suppression on 5.56x45mm weapons. The gas dynamics of the Dead Air Sandman-S are most similar to that of the Rugged Razor556. Both those silencer produce similar holistic signatures to that of the Surefire SOCOM762-RC2 on the MK18. However, the RC2 series, with its more advanced flow paths, produces the most consistent gas dynamics of the three silencers.
The user may choose to install a 5.56 mm bore end cap in place of the standard 30 caliber endcap on the Dead Air Sandman-S. The use of the 5.56 mm end cap changes the gas dynamics, and thus the suppression performance, of the Sandman-S on this platform. This phenomenon is explored in PEW Science Member Research Supplement 6.93.
The ratcheting proprietary mount welded to the rear of the Sandman-S that interfaces with Dead Air KeyMo muzzle devices is relatively simple to operate. The mount can facilitate the installation of the silencer underneath a handguard or on barrels that have exterior obstructions which may prevent the fastening of traditional locking collars. This capability is achieved by rotating the entire silencer body during installation, rather than actuating a localized mount ring or lever. However, it is important to note that radiant heat during use of a silencer placed under the handguard of a semiautomatic rifle can be significant. PEW Science urges users to consider radiant heat when deciding on specific silencer mounting configurations.
The Sandman-S is marketed to be durable and is advertised to not have any restrictions on barrel length; therefore it may be used with aggressive semiautomatic and automatic firing schedules. Despite this allowance, the designers of the silencer rate the system for pressures generated by cartridges up to 300 Winchester Magnum and not a higher pressure rating (300 Remington Ultra Magnum, for example). It is postulated that the reduction in rating is due to the KeyMo system limitations. Therefore, PEW Science encourages the user to contact the silencer designer prior to use with high power magnum rifle cartridges. This caution may not be intuitive to some users due to the Sandman-S being marketed as a machine gun silencer. Note that this paragraph is a carry-over from the .308 bolt-action review of the Sandman-S and is repeated here, as this information was accurate at the time of that publication and those silencers are still in circulation.
In this review, the Sandman-S 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.
