SSS.6.76 - Rugged Razor556 and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle
/Rugged Razor556 on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The Razor556 is manufactured by Rugged Suppressors. It is a 223 caliber centerfire rifle silencer, intended to suppress the 5.56x45mm NATO cartridge. It has a 1.5-inch diameter and is 6.4 inches in length. Like other Rugged rifle silencers, the endcap is removable and interchangeable to accommodate other apertures. However, the endcap possesses features integral to the holistic design of the Razor556 and differs from the Rugged 5.56mm endcap. The user may choose from various Rugged muzzle devices on which to mount the silencer to the host weapon with its welded proprietary dual-taper locking mount. The outer tube and mount are stainless steel and the cast Stellite baffles of the inner core are fully-welded. The silencer weighs 13.5 ounces and the included 5.56mm M2 muzzle brake weighs 1.8 ounces, for a total system weight of 15.3 ounces, as tested. The Razor556 can be obtained from Silencer Shop.
This Sound Signature Review contains single-test results using the Rugged Razor556 with the M2 muzzle brake 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 6.76.1 contains the Razor556 test results and analysis. The Razor556 is not the same silencer as the Razor762, in construction, features, or performance.
Section 6.76.2 contains contains Suppression Rating comparisons of the Razor556 with dedicated 223 and 30 caliber silencers on the current market, including the Otter Creek Labs Polonium, Surefire SOCOM556-RC2, HUXWRX HX-QD 556, Q Trash Panda, CGS Helios QD, SilencerCo Saker 556, Rugged Razor762, and others.
Section 6.76.3 contains the review summary and PEW Science subjective opinions.
Note that PEW Science Member Research Supplement 6.77 contains comparative analysis of the performance of the Razor556, the Razor762 with its standard 30 caliber endcap, and the Razor762 using the 5.56 mm endcap on the MK18.
Summary: When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the Rugged Razor556 mounted with the M2 muzzle brake mount achieved a composite Suppression Rating™ of 24.3 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
6.76.1 Razor556 Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the Razor556 tested with the M2 muzzle brake 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. Rugged Razor556 Sound Metric Summary
6.76.1.1 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 Razor556 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 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. Rugged Razor556 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. Rugged Razor556 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature
Figure 2a. Rugged Razor556 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. Rugged Razor556 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
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 Rugged Razor762 in Review 6.58. One of the most significant differences is the delayed shock rise from the Razor556 on the MK18 (Fig 1b). Like the Razor762, the Razor556 produces a coupled bullet shock and muzzle blast jet event in early time, which is a consequence of the over-bore present in each silencer for the 5.56x45mm NATO cartridge. The consistent rise time and jet delay present in the Razor556 signatures is postulated to be the result of two primary factors:
Razor556 endcap orifice geometry (jet nozzle recess and exterior nozzle chamfer).
Baffle quantity and spacing (the Razor556 possesses three baffles, in contrast to the four in the Razor762).
The above two factors result in both differing internal muzzle blast jet expansion and external muzzle blast jet propagation, when using the Razor556 instead of the Razor762 on the MK18.
PEW Science Research Note 1: Note the less severe early time rarefaction following the primary muzzle blast with the Razor556 (Fig 1b) than with the Razor762 (Fig. 1b, SSS.6.58.1.1). PEW Science postulates this to be a direct result of jet nozzle orifice shape and recess (endcap features). Furthermore, the differing internal jet expansion timing, facilitated by the removal of baffle 3 and repositioning of baffle 2, induces a distinct difference in primary muzzle blast impulse accumulation. This prolonged positive phase event is characterized by the longer duration impulse plateaus from the Razor556 (Figure 2), compared with the expedient impulse decay from the Razor762 (Fig. 2a, SSS.6.58.1.1). PEW Science postulates that these changes allow the Razor556 to utilize over-bore more efficiently than the Razor762 on the 5.56x45mm MK18 weapon system.
PEW Science Research Note 2: The above geometric changes in the Razor556 from the Razor762 influence gas flow rate and timing; the flow restriction (back pressure) of the Razor556 is postulated to slightly increase when compared to that of the Razor762, despite the Razor556 possessing one less baffle. PEW Science postulates that this slight decrease in flow rate is a direct result of the aforementioned increase in over-bore efficiency on the short-barrel 5.56x45mm platform. The internal expansion volume (interstitial baffle space) in the Rugged Razor556 may initially relieve high pressure stagnation of the 5.56x45mm cartridge muzzle jetting in early time. PEW Science further postulates that this stagnation relief, facilitated by jet expansion, reduces flow rate in the absence of baffle stack venting. Internal research is ongoing. Note that this simple method of stagnation relief may produce erratic flow rate during subsequent shots, depending on shot timing. It should also be noted that the impulse consistency of the Razor556 is greater than that of the Razor762, but still possesses erratic characteristics typical of over-bore.
The aforementioned changes in the Razor556 from the Razor762 increase 5.56x45mm SBR suppression efficiency, on average. For example, the Razor556 is able to produce a muzzle Suppression Rating (to bystanders) on par with that of the much larger Surefire SOCOM762-RC2 (Review 6.73) on the MK18, with significantly less baffles. Both silencers are over-bored for the 5.56x45mm cartridge. Both silencers possess very similar flow rates (back pressure) in the 5.56x45mm flow regime. However, the SOCOM762-RC2 places the endcap orifice further from the shooter’s head; this pressure source standoff, along with sound field differential, results in the Razor556 possessing a more severe signature, to the shooter (ear Suppression Rating).
The Razor556 is not as efficient as some other over-bored silencers for the 5.56x45mm platform, such as the CGS Helios QD (Review 6.66) and the Q Trash Panda (Review 6.61), both of which possess more sound suppression to bystanders and to the shooter on the MK18, but at the expense of greater size and back pressure. Dedicated-bore 5.56x45mm silencers like the Surefire SOCOM556-RC2 (Review 6.52), the SilencerCo Saker 556 (Review 6.53), and the Otter Creek Labs Polonium (Review 6.75) produce noticeably less severe signatures to bystanders on the MK18 weapon system, at the expense of significantly higher back pressure.
The measured first-round-pop (FRP) from the Razor556 is visible in both the pressure regime (Figure 1b) and the impulse regime (Figure 2b), 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 Razor556 is postulated to not be immediately noticeable to bystanders, in accordance with PEW Science inner ear modeling.
Although the Razor556 and Razor762 share many design features, the differences are numerous enough that the Rugged Razor556 is quieter than the Rugged Razor762 on the MK18 weapon platform, to both bystanders and to the shooter, on average.
PEW Science Research Note 3: 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 83 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 4: 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.
PEW Science Research Note 5: Note that the muzzle Suppression Rating of the Rugged Razor556 with the M2 muzzle brake mount is 22.0 and the at-ear Suppression Rating is 19.2; the same zone on the Suppression Rating Dose Chart. The more efficient muzzle Suppression Rating of the Razor556 contributes to a less severe at-ear Suppression Rating when compared to that from the Rugged Razor762 on the standard MK18 weapon system. This occurs despite the Razor556 possessing slightly higher back pressure. Regardless of the shooter’s ear signature advantage, as with the use of many silencers on the standard MK18, caution should be exercised by the weapon operator. The signatures measured at the shooter’s ear are presented below.
6.76.1.2 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, 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. Rugged Razor556 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature
Figure 3b. Rugged Razor556 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 4a. Rugged Razor556 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature
Figure 4b. Rugged Razor556 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature Peaks
Unlike in the measurements at the muzzle, the FRP from the Razor556 at the shooter’s ear is noticeable. The contributing factor to the shooter’s ear FRP is most easily discernable in Figure 4b at approximately 30.5 ms where ancillary combustion results in higher early-time impulse. The overall impulse at the shooter’s ear is erratic, but more consistent than measured from the Razor762 (Fig. 4a, SSS.6.58.1.1).
PEW Science Research Note 6: Other adverse conditions are also observed at the shooter’s head position. As discussed in Research Note 2, one of the methods by which the Razor556 gains efficiency over the Razor762 on the MK18 is internal gas expansion volume (the absence of a baffle). During the first shot, this geometric change works as intended. Subsequent shots induce a change in flow rate, evidenced by increased late-time rarefaction (Fig 3b). PEW Science test data and inner ear modeling indicate that this adverse flow rate change may reach a maximum midway through a shot string and normalize during continuous fire. Note that the timing of this increase in backpressure severity may be difficult to predict. PEW Science postulates that the flow rate changes from the Razor556 are a consequence of the behavior of gas in the volume between baffle 2 and baffle 3; this may be indicative of a flow rate change that is highly dependent upon rate of fire (e.g. so-called “gas stack” which is a phenomenon most often observed during the continuous automatic firing of suppressed weapons, in which interstitial volumes become pressurized for durations that are long relative to vessel blow-down, and gas flow paths within the silencer shift dynamically).
The late-time rarefaction events shown in Figure 3a are only present in one shot (Shot 5) of the Razor762 test (Fig. 3a, SSS.6.58.1.1). This is a direct illustration of the slightly higher backpressure from the Razor556 than present in the Razor762, and also an example of the inherent uncertainty of gas behavior and flow rate consistency when using silencers with significant over-bore on a weapon platform.
Despite the aforementioned flow uncertainties, the change in gas dynamics (slightly higher back pressure), and the simple methods by which the Razor556 gains efficiency on the MK18 weapon system, the Razor556 is a more optimized silencer for the 5.56x45mm cartridge than the Razor762, on average. The shooter’s ear signatures are significantly influenced by the reduced severity of the Razor556 muzzle signature. Both Razor silencers are short; the endcap proximity to the shooter’s head position on the MK18 is a significant contributing factor to shooter’s ear suppression performance. This factor remains, regardless of flow rate (back pressure).
Note that the rarefaction events at the shooter’s ear in late time are not as severe as higher back pressure silencers like the SilencerCo Saker 556 and Otter Creek Labs Polonium. This difference is due to primary bore blast propagation; the predominant variable governing overall flow rate in conventional silencers. Recall the below factors presented in Review 6.75:
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.
6.76.2 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 13 presents a comparison of the PEW Science Suppression Rating of the Rugged Suppressors Razor556 with the M2 muzzle brake 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 Rugged Razor556 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 Razor556 suppressor has significantly higher sound suppression performance to bystanders than the Razor762, on the MK18 weapon system, on average. The Razor556 is able to produce a muzzle Suppression Rating (to bystanders) on par with that of the much larger Surefire SOCOM762-RC2 on the MK18, with significantly less baffles. Both silencers are over-bored for the 5.56x45mm cartridge, but the Razor556 is optimized for the platform (see Research Note 1 and Research Note 2 in Section 6.76.1.1).
PEW Science Research Note 7: At the shooter’s ear, the suppression advantage of the Razor556 over that of the Razor762 with its 30 caliber endcap is measurable, but less pronounced than the advantage at the muzzle. This is a direct consequence of both the slightly increased back pressure of the Razor556 and the significantly increased muzzle (bystander) Suppression Rating of the Razor556. The balance of these two variables results in a net influence, to the shooter, that is not largely significant. It is important to note that the Suppression Rating is highly dependent upon weapon platform. Use of the Rugged Razor556 and Razor762 on other 5.56x45mm weapon systems may produce results that differ from the comparison above.
The aforementioned changes (Section 6.76,1.1) in the Razor556 from the Razor762 increase 5.56x45mm SBR suppression efficiency, overall. However, the Razor556 is not as efficient on the MK18 as some other over-bored silencers for the 5.56x45mm platform, such as the CGS Helios QD and the Q Trash Panda, both of which possess more sound suppression to bystanders and to the shooter on the MK18, but at the expense of greater size and back pressure. Dedicated-bore 5.56x45mm silencers like the Surefire SOCOM556-RC2, the SilencerCo Saker 556, and the Otter Creek Labs Polonium produce noticeably less severe signatures to bystanders on the MK18 weapon system, at the expense of significantly higher back pressure.
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.
Note that PEW Science Member Research Supplement 6.77 contains comparative analysis of the performance of the Razor556, the Razor762 with its standard 30 caliber endcap, and the Razor762 using the 5.56 mm endcap on the MK18.
6.76.3 Review Summary: Rugged Razor556 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 Rugged Razor556 mounted with the M2 muzzle brake mount achieved a composite Suppression Rating™ of 24.3 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 Rugged Razor556 is a “semi-compact” 223 caliber machine gun rated rifle silencer that possesses moderate sound signature suppression performance with relatively low back pressure. Relative to many dedicated 5.56mm bore silencers, it may be considered “full size.” The silencer is lighter than the Razor762 and quieter than the Razor762 on the MK18 5.56x45mm short-barrel rifle AR15 weapon system, on average. The Razor556 is advertised to have extreme durability and possesses a total system weight of 15.3 ounces, as tested.
Like the Razor762, the Rugged Razor556 uses an iteration of a feature-reduced and modified curved-cone baffle, similar to the feature-reduced curved-cone baffle used in the Omega 300 from SilencerCo and other companies. The Razor556 possesses only three baffles (one less than the Razor762). PEW Science postulates that the increased expansion volume and baffle spacing differential results in a simplified pressure stagnation relief zone, increasing suppression efficiency on the 5.56x45mm platform. On the 10.3-in barrel MK18, this modification results in flow rate changes that may increase back pressure during continuous fire. Regardless, the increased efficiency in muzzle Suppression Rating allows the Razor556 to outperform the Razor762 in sound signature suppression to both the shooter and to bystanders on the MK18, on average.
The endcap of the Razor556 is not the same as the 30 caliber or 5.56mm endcaps offered by Rugged for use on the Razor762. As discussed in this article, there are distinct design changes to the Razor556 endcap that are postulated to influence performance on the 5.56x45mm platform. The use of different endcaps may change gas dynamics. Comparisons of the Razor556 and the Razor762 with its different endcaps, are explored in PEW Science Member Research Supplement 6.77.
The dual-taper locking proprietary mount welded to the rear of the Razor that interfaces with Rugged muzzle devices is relatively simple to operate. To install the silencer, the user must thread it onto a coarse-thread mount, which engages a forward taper, and then engage the locking collar which compresses cam levers onto a secondary rear taper. The mount is very secure. PEW Science anecdotal experience with the Rugged mount across various Rugged rifle silencers and host weapons has been overwhelmingly positive. However, it is possible to rotate the silencer on the mount, when locked, if significant rotational force is exerted. Note that the Razor556 includes the M2 muzzle brake mount, threaded 1/2”-28tpi.
The Rugged Razor556 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. The combination of durability and relatively low back pressure makes the Razor556 a reasonable choice for semiautomatic and automatic centerfire rifle use, particularly for cases in which both weight and back pressure are a concern. The Razor556 is 2 ounces lighter than the Razor762.
In this review, the Razor556 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.
