SSS.6.191 - Combat Application Technologies CAT/RAT and the Sig MCX 300 BLK Short Barrel Semiautomatic Rifle (Free Version)
/Combat Application Technologies CAT/RAT on a 300 BLK SIG SAUER MCX Virtus TACOPS with 6.75-in Barrel
The CAT/RAT (“RAT” in this report) is designed by Combat Application Technologies (CAT). It is a multi-unit modular silencer system intended to suppress the 300 BLK cartridge on reciprocating personal defense weapons (PDWs) with both supersonic and subsonic ammunition. Design functionality of the RAT system is specifically tailored to the SIG SAUER MCX and Rattler family of PDWs. The RAT system variant examined in this report possesses a 1.7-inch diameter and is adaptable in three distinct configurations: Base, FLOW, and COVERT. SIG SAUER includes a bushing to adapt the host weapon’s 5/8-24 tpi SIG-tapered (25-deg) muzzle for use with 90-deg shoulder muzzle devices. The bushing was used in this test program with a 90-deg AI NANO muzzle device that uses the 1-16 tpi LH silencer thread mount system with rear wrench flats. Both 90-deg and SIG taper AI NANO muzzle devices are included with all CAT RAT retail packages. The RAT system lengths are 3.75-in (Base), 7.75-in (FLOW), and 7.66-in (COVERT) from muzzle device shoulder to distal silencer end, inclusive of the 0.5-in long Base module male coupler when in that configuration. The entirety of the silencer system is DMLS (3D-printed) from a proprietary titanium alloy, and the AI NANO mount is 17-4 heat treated stainless steel. The silencer sections each individually weigh 7 oz, 6.2 oz, and 5.7 oz, respectively and the AI NANO mount weighs 2 oz. Therefore, total system weights are 9 oz (Base), 15.2 oz (FLOW), and 14.7 oz (COVERT), as tested. The CAT RAT system can be obtained from Silencer Shop or Combat Application Technologies in three package configurations (COVERT+Base Assembly, FLOW+Base Assembly, and a complete kit with all three modules).
PEW Science is an independent private testing laboratory and also hosts the world’s only independent public suppressed small arms research cooperative. Testing, data analysis, and reporting is generated with funding provided by PEW Science members. Any test data that is generated with any portion of private funding contains this disclosure. The testing and analysis production for this Sound Signature Review was funded in part by PEW Science Project PEW-CAT-059-005-25. Therefore, data pertaining to the CAT/RAT in this Sound Signature Review is published with the express written permission of Combat Application Technologies.
The testing and analysis presented in this Sound Signature Review are of the CAT RAT in three different configurations on the SIG SAUER MCX Virtus TACOPS AR-18 derivative semiautomatic rifle, chambered in 300 AAC Blackout with a 6.75-inch barrel. This weapon system is the consumer retail analog to the USSOCOM Low Visibility Assault Weapon (LVAW). Discreet Ballistics 190gr 300 BLK subsonic ammunition was used in the test. Gas system parameter measurements of the 6.75-in SIG SAUER MCX system are presented on the PEW Science Small Arms Technical Data page. Please note the specific gas system setting used in the tests as displayed in each Test Summary Table, as well as in each Test Data Plot in this report.
Section 6.191.1 contains a CAT RAT and SIG SAUER MCX system operation overview to illustrate system design and applicability metrics that may assist the end user in understanding system selection and use case variables.
Section 6.191.2 contains CAT RAT COVERT system test results and analysis.
Section 6.191.3 contains CAT RAT FLOW system test results and analysis.
Section 6.191.4 contains CAT RAT Base system test results and analysis.
Section 6.191.5 contains overall Suppression Rating comparisons of all three CAT RAT configurations on the 6.75-in SIG SAUER MCX System.
Section 6.191.6 contains an article summary and PEW Science laboratory staff opinions.
Summary: When paired with the 6.75-in barrel SIG MCX and fired with Discreet Ballistics 190gr 300 BLK subsonic ammunition, the CAT RAT in the COVERT configuration achieved a Suppression Rating™ of 62.2 in PEW Science testing. In the FLOW configuration, the CAT RAT achieved a Suppression Rating of 47.6. The CAT RAT base configurations with no extensions achieved a Suppression Rating of 25.6.
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.
6.191.1 CAT RAT and SIG SAUER MCX / Rattler 300 BLK System Operation Overview
To date, the PEW Science Silencer Sound Standard public research pedigree has included evaluation of silencer performance with subsonic 300 BLK ammunition on 8-in bolt-action rifle to study pure combustion propagation phenomenology from one primary blast load vent orifice. Performance comparisons may be viewed in the comprehensive performance Rankings tabulated in Section 7 of the Standard. The scope of this report marks the addition of semiautomatic 300 BLK public suppression performance evaluation in the Standard.
The SIG SAUER MCX family of weapon systems is offered in a variety of cartridge chamberings, barrel lengths, gas system length configurations, and variant generations. Full historical discussion of the MCX family is outside the scope of this report. Pertinent system information is presented in this section.
6.191.1.1 SIG SAUER MCX 300 BLK System Characteristics
The entire family of MCX weapon systems are AR-18 rifle derivatives. Unlike the AR-15 rifle system exemplified by the PEW Science standard MK18 Tests Host (6.51) and standard M4A1 Test Host (6.127), which are both direct-impingement gas-operated rifles, AR-18 systems are short-stroke gas piston-operated rifles. There are two primary differences between the AR-15 and AR-18 systems:
Blast Load Momentum Application: In a direct-impingement AR-15 system, expanding combustion gasses are routed from a flow orifice at the top of the barrel into a secondary expansion chamber (gas block), and then into tertiary expansion chamber (gas tube), where they further expand and impart momentum to a bolt carrier group (BCG) to facilitate weapon action reciprocation. In a short-stroke gas piston AR-18 system, expanding combustion gasses are instead routed into a gas block that contains a linearly-actuated piston of fixed mass and dimension that is physically decoupled from the BCG. The piston is permitted to move through a fixed dimension of travel, impart its momentum to the BCG, and the decoupled BCG is then driven rearward to facilitate weapon action reciprocation. In some AR-18 operating systems, the gas block possesses a vent to atmosphere that serves the function of regulating internal gas block blast load impulse accumulation subsequently imparted to the piston. This is not the case with the 6.75-in 300 BLK SIG MCX operating system. The 300 BLK MCX system gas block does not possess a dedicated atmospheric vent. The 300 BLK piston is fitted with a spiral gas ring that effectively seals the interface between the piston and the gas block in the range of piston travel. The reader is encouraged to examine the measurements and photographs of the system shown on the PEW Science Small Arms Technical Data page.
Recoil System Mechanics: In the classical AR-15 operating system, whether direct-impingement or piston operated, the recoil system components consist of cam-delayed bolt unlock from the barrel extension, BCG inertial resistance, recoil buffer inertial resistance, and recoil buffer spring resistance. It is the buffer spring, housed in a rear buffer tube, that returns the BCG to battery upon the return-stroke in the system operation. In the AR-18 operating system, there is no buffer or buffer spring assembly. Instead, there are recoil springs housed in the upper receiver. These springs are captured by guide rods, and return the BCG to battery after short-stroke reciprocation is complete. This enables the weapon stock assembly to be mechanically decoupled from the recoil system assembly, thus simplifying “folding” capability and other mechanical adaptations. The SIG MCX adopts this AR-18 recoil system and can therefore be equipped with a variety of stock assemblies.
Both gas operation (1) and recoil operation (2) influence the blast overpressure signatures to which bystanders and the operator is subjected when suppressing the SIG MCX. Furthermore, there are system idiosyncrasies that result from the adaptation of the AR-18 operating system used in the SIG MCX with subsonic 300 BLK cartridge combustion. SIG SAUER designed system adjustability components to address potential issues. These components are discussed below.
The 300 BLK MCX system is offered in several generations and barrel lengths, including 5.5-in, 6.75-in, and 9-in. Generational adaptations include “Rattler” models, along with “MCX” models. There exist at least 3 to 4 generations of models: Gen 1 MCX, Gen 2 VIRTUS, Gen 3 SPEAR-LT, and Rattler variants existing in parallel. The current Rattler LT variants are more similar to MCX variants than previous Rattler units. The reader is encouraged to contact SIG SAUER for exact configuration differences and parts compatibility.
All MCX systems possess two-position adjustable gas valves. The 300 BLK MCX systems have specific instructional parameters, as provided by SIG SAUER in the weapon manual (Fig. 1). Measured gas system port sizes for the “+” and “-” settings on the 6.75-in barrel system are presented on the PEW Science Small Arms Technical Data page. The user should note that there exist multiple gas valves available from SIG SAUER. Gas valve designations F01 and F03 were included with the retail package of the 6.75-in VIRTUS system used in this test report. Per SIG SAUER, the F01 valve is intended for high back pressure (traditional) silencer use with the 6.75-in system. The F03 valve is intended for low(er) back pressure (higher flow rate) silencer use with the 6.75-in system. It is important to note that gas valve port size is not the only difference between MCX gas valves. Both the internal depth and diameter of the F01 valve are larger than in the F03 valve. Therefore, the F03 gas valve has smaller internal expansion volume and enables a higher amplitude of gas impulse transfer through the ports. Blast load expansion, along with port size, creates the coupled mechanism needed for system operation.
The 6.75-in MCX VIRTUS with the F03 valve switched to the “+” setting was used in this test program.
Figure 1. SIG SAUER MCX Two-Position Gas Valve Instruction Manual Pages 44-45.
As noted in Figure 1 above, some 300 BLK models may not reliably function without a silencer installed. Furthermore, after significant SIG SAUER MCX system proliferation into the consumer retail market, other issues have been known to occur:
When unsuppressed, the system may under-function with certain ammunition types.
When suppressed, the system may under-function or over-function with certain silencers, certain ammunition types, and various combinations of both.
When adapting high back pressure silencers to force function on under-functioning guns, the user may experience significant “gas blowback” regardless of gas valve adjustment, as well as system malfunctions.
When adapting low back pressure silencers to mitigate “gas blowback,” the system may be unreliable with regard to function with many ammunition types, and malfunctions may occur unpredictably. This is due to the mechanism(s) of back pressure reduction used in many “high flow rate” silencers.
The CAT RAT system was developed to address these issues.
6.191.1.2 CAT RAT 300 BLK Silencer System Characteristics
The CAT RAT system includes multiple variants, one of which is evaluated in this report, in three of its configurations. The PEW Science laboratory has evaluated multiple RAT system variants on multiple host weapons; the RAT program was initiated to address issues with fielded weapon systems as described above and also to give the user adaptable performance attributes based upon use case.
Weapon System Operation Note: The testing and analysis presented in this report of all three RAT configurations uses the F03 gas valve in the 6.75-in weapon system on the “+” setting, as discussed in the previous section. The F01 gas valve “+” setting also provides function of the 6.75-in MCX VIRTUS 300 BLK system with the CAT RAT. However use of the F01 gas valve may result in a BCG failure to lock back on empty magazine malfunction if firing the weapon unshouldered, limp-wristed, or “from the hip.” This malfunction could be induced by PEW Science laboratory staff only if firing in such manners, and with the last round in the magazine. For this reason, PEW Science (and SIG SAUER) recommend the use of the F03 gas valve when suppressing the 6.75-in 300 BLK MCX system with modern high flow rate or hybrid silencers. Please see the measured port size and gross volumetric expansion differences of the F01 and F03 gas valves on the PEW Science Small Arms Technical Data page. Again, port size is not the only difference between the two valves.
Regardless of CAT RAT configuration used, function of the 300 BLK system is intended to be maintained. The only system adjustments that should be needed when using the CAT RAT in any configuration with the SIG MCX system are:
If using supersonic 300 BLK ammunition, the “-” gas valve setting is permitted and recommended.
If using subsonic 300 BLK ammunition, the “+” gas valve setting is mandatory.
The three different CAT RAT configurations evaluated for the retail variant presented in this report include:
RAT Base: This configuration provides the most compact and lightest weapon system configuration while still significantly reducing blast overpressure hazard to the operator and bystanders when compared to an unsuppressed system. The length and weight are 3.75-in / 9 oz with mount. It is intended for vehicle operations and other environments in which the smallest weapon package is required. Early-time blast load impulse accumulation (alpha parameter) is low. Late-time gas momentum restriction (PEW Science Omega Metric) is also low. Gas blowback to which the operator is subjected is therefore low.
RAT FLOW: This configuration provides a balance of blast overpressure protection (PEW Science Suppression Rating), low gas blowback, and overall signature suppression performance, in the longest and heaviest envelope; 7.75-in / 15.2 oz with mount. It is intended for training operations and/or high-volume fire. Early-time blast load impulse accumulation remains unchanged from the Base configuration. Late-time gas momentum restriction (PEW Science Omega Metric) is increased, but gas blowback to the operator remains low.
RAT COVERT: This configuration provides the highest degree of overall signature suppression performance in the 2nd-longest and heaviest envelope; 7.66-in / 14.7 oz with mount. It is intended for discrete operations. Early-time blast load impulse accumulation remains unchanged from the Base configuration. Late-time gas momentum restriction (PEW Science Omega Metric) increases to maximum. However, operator blast overpressure protection (shooter’s ear Suppression Rating) nominally increases when compared to the FLOW configuration, as reduced muzzle blast loads more than compensate for the elevated omega state. Gas blowback during rapid fire will be elevated, when compared to the other two configurations.
The blast overpressure protection capabilities of all three configurations of the CAT RAT variant tested in this program are summarized in Figure 2 below. 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. Due to its true free field test data origin and complete waveform analytical calculation basis, it is the only known universal suppressed weapon system signature comparison metric available.
Figure 2. Suppression Rating Comparisons of the CAT RAT configurations, Using PEW-SOFT 300 BLK Subsonic SIG MCX AR-18 Test Data and PEW Science Analysis
From the above semiautomatic short-barrel AR-18 rifle performance metrics, it can be concluded that signature suppression levels may increase or decrease in accordance with not only distal blast momentum propagation rate, but also in accordance with other signature components that vary based on silencer internal design. Furthermore, it is extremely important to note that the early-time flow rate of a silencer and pure gross suppression capability may also influence performance. For example, the FLOW configuration of the CAT RAT has the same early-time flow rate as the COVERT configuration. But, their late-time flow rates differ significantly, as do their gross suppression capabilities. Regardless, their shooter’s ear Suppression Ratings are similar. This is because in the free field, the more severe blast loads propagating from the distal end of the FLOW silencer configuration expand three dimensionally and somewhat counteract the ejection port blast hazard reduction of the system. In the case of the COVERT configuration of the RAT, the constant early-time flow rate derived from the Base configuration remains constant and operator blast overpressure protection is not compromised. The only adverse condition increase with the COVERT configuration for the weapon operator will be gas blowback during rapid fire when compared to other two configurations.
Outside the free field environment, the FLOW configuration may induce more severe blast load reflections than the COVERT configuration, which will impact both shooter’s ear (operator) and muzzle (bystander) Suppression Rating metrics.
Full subsonic 300 BLK 6.75 SIG MCX AR-18 evaluation of the CAT RAT in COVERT, FLOW, and Base configurations follows.
6.191.2 CAT RAT COVERT Configuration Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the CAT RAT in the COVERT configuration is shown in Table 1. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. The data acquired 0.15 m (6 in) right of the shooter’s ear is only available to membership supporters of PEW Science and the Silencer Sound Standard. You can support public PEW Science testing, research, and development with a membership, here. State-of-the-art public firearm sound signature testing and research conducted by PEW Science is supported by readers like you.
Table 1. CAT RAT COVERT Configuration Sound Metric Summary
6.191.2.1 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 CAT RAT COVERT configuration are shown in Figure 3a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 3b, 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 Shots 2 and 3.
Fig 3a. CAT RAT COVERT Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Pressure Signature
Fig 3b. CAT RAT COVERT Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Sound Pressure Signature
Figure 4a. CAT RAT COVERT Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Impulse Signature
Figure 4b. CAT RAT COVERT Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Impulse Signature
The CAT RAT system, in all configurations, is classified as a hybrid design in the PEW Science research taxonomy. More specifically, the RAT is classified as a modular staged hybrid. Hybrid design silencers are those in which elements of both conventional and high flow rate silencers are used, coupled with other technology variations and staged elements to provide parametrically varied performance attributes. Such attributes include the ability to reduce early-time shock reflections while significantly altering the rate of proximal and distal venting. These silencers may allow for minimal reciprocating weapon functional influence, while at the same time significantly suppressing signature to the operator and bystanders. Hybrid designs span a large range of the market in both brand and performance in different combustion regimes. There also exist subcategories of this class of silencers that have been shown to demonstrate efficacy in multiple flow regimes. Discussion of these subcategories is outside the scope of this report. Other hybrid designs and staged hybrids include those from PTR, CAT, CGS, SilencerCo, Surefire, recently Otter Creek Labs, and others. For an overview of the three primary classes of rifle silencer designs, the reader is encouraged to review PEW Science Research Supplement 6.169.
Various CAT SkyNET system technologies have previously been evaluated by PEW Science and are each utilized to achieve different performance characteristics on the requisite weapon system platforms. These technologies include:
SB-SHOCK in the CAT SC (6.162)
SURGE BYPASS in the CAT SR (6.141), CAT ODB (6.120), CAT WB (6.130), and CAT DD (6.159)
DiVerge in the CAT MOB (6.148)
SNIPER2 in the CAT JL (6.147)
The CAT RAT system is modular not in “end cap” change but in complete adaptation using CAT A-PULSE technology, which is a modular adaptation of SB-SHOCK and SNIPER2. The Base RAT configuration effectively modulates the alpha state not to drop below a critical value by delaying early venting more than typical through an increase in initial shock pulse clearing time. Tuned for the MCX system, this allows A-PULSE to manage early-time flow rate consistently regardless of downstream blast momentum propagation, which is a key design parameter for the SIG MCX system. And, because the COVERT and FLOW extensions are truly downstream modules, A-PULSE functions with both subsonic and supersonic 300 BLK ammunition, regardless of the RAT configuration chosen by the user.
The CAT RAT modular sytem is characterized by the following physical design attributes:
In the Base module, early venting in the first expansion (blast) chamber prevents excessive blast load impulse accumulation in early time. The included AI NANO muzzle devices produce radial jet impingement upon reinforced walls of the chamber while downstream reflections are routed to a vent path. The alpha state is precisely tuned such that MCX weapon function can still take place with only the Base module fielded. Addition of the COVERT or FLOW module to the base module then enhances function, without over-function.
With the COVERT module attached to the RAT Base, the early venting does not change; alpha remains constant and multiple staged pressure relief components are used to manage downstream blast momentum control during the entire shot string, inclusive of first-round-pop (FRP). This Omega Metric increase is further produced by the lack of external venting to atmosphere in this configuration, other than from the distal primary bore aperture.
With the FLOW module attached to the RAT Base, early venting again does not change. The PEW Science Omega Metric drops from that in the COVERT configuration as multiple vent paths are activated in the extension module and blast loads are vented to atmosphere at the distal end through angled ports. The vent angles are not parallel to the bore line.
PEW Science Research Note 1: Although all CAT silencers are weapon-system optimized, the CAT RAT represents perhaps one of the most strict optimization cases evaluated by PEW Science in the CAT design pedigree. When the Base module is fitted with the COVERT extension, the CAT RAT functions as a 300 BLK rifle silencer with a high early-time flow rate and a restricted late-time flow rate. This performance is demonstrated by the following characteristics shown in the above test data:
Relatively longer blowdown duration (Fig. 3a).
Lack of decoupled ground reflection, consistent with (1).
Relatively low amplitude initial coupled jetting with very short initial positive phase blast load duration (Fig. 3b), along with blast momentum significantly throttled externally in early time (Fig. 4a).
FRP divergence occurs well after peak blast pressure propagation (Fig. 3b).
Relatively long positive phase blast impulse accumulation duration for the cartridge (Fig. 4a).
Post-FRP secondary accumulation reaches FRP amplitude (Fig. 4b).
The strict optimization statement above is made because in conjunction with all six behavioral traits measured in this test, the cyclic rate of the weapon system is not significantly influenced when compared to the FLOW configuration. This is a result of the constant alpha state in the base module and the gas sensitivity of the 6.75-in 300 BLK SIG MCX weapon system. Therefore, the user may employ the COVERT module and only concern themselves with an increase in blowback during rapid fire compared to the use of the FLOW module; not a change in weapon system function or reliability.
PEW Science Research Note 2: PEW Science 6.75-in 300 BLK subsonic SIG MCX AR-18 system research is still ongoing. As it stands, the weapon system provides two distinct differentiations from the existing 8-in barrel 300 BLK bolt-action system research pedigree, to date:
Barrel Length: The shorter 6.75-in barrel results in multiple performance variables for blast load input in the silencer system. It produces higher muzzle blast pressure and also lower projectile pressure wave amplitude in the subsonic ammunition combustion regime. Different silencers will react differently to this change in barrel length, with regard to pure muzzle suppression performance. As it stands, the CAT RAT COVERT configuration produces a 62.1 muzzle (bystander) Suppression Rating on this system. The muzzle signatures displayed above consist of internal blast propagation, distal orifice blast pressure propagation, ejection port blast propagation, and weapon system mechanical operation. All of these waveform components combine to form the complete signature displayed in Figure 3a. If the reader is to compare a performance analog in subsonic 300 BLK combustion suppression from the existing pedigree to date, a similar muzzle Suppression Rating of 63.8 was obtained by the Resilient Suppressors Jolene (6.138) on the 8-in barrel bolt-action test platform (no ejection port blast and no mechanical operation other than the trigger actuation and firing pin drop). With its direct-thread mount, the Jolene is 9.1-in long compared with the 7.66-in long RAT COVERT. The RAT also has an exceedingly higher flow rate than the Jolene, as well as significantly more robust FRP suppression. The Otter Creek Hydrogen-L (6.94) and SIG SAUER SRD762TI-QD (6.39) achieve a 65.1 muzzle Suppression Rating on an 8-in barrel bolt-action rifle. Both of those silencers are larger and possess significantly lower early time flow rate than the CAT RAT COVERT. With lower early time flow rate, ejection port blast hazards on semiautomatic platforms increase.
Ejection Port Blast Loads: The 6.75 SIG MCX AR-18 is a semiautomatic weapon system. As demonstrated in the 115 other existing reciprocating weapon system test data records in the Rankings to date (semiautomatic rifle or pistol), ejection port blast loads may significantly influence operator hazard and therefore impact the shooter’s ear (operator) Suppression Rating. As it stands, the CAT RAT COVERT configuration produces a 41.8 operator Suppression Rating on this system, in the free field. As more test records are populated with subsonic 300 BLK combustion from semiautomatic systems, comparison points will be generated. For now, the reader may consider the differential between an operator Suppression Rating in the 40-zone and an operator Suppression Rating for the entire semiautomatic dataset to date, including both supersonic 5.56x45mm NATO combustion, and subsonic 9x19mm combustion, omitting subsonic .22LR rimfire. The highest shooter’s ear Suppression Rating published on a standard untuned 5.56 semiautomatic rifle is 32.4 from the low back pressure HUXWRX FLOW 556 Ti (6.167). A high back pressure silencer, the Maxim Defense DSX, achieved a 32.5 shooter’s ear Suppression Rating on the tuned SURG system (6.111) and only 22.0 on the standard untuned system (6.110). Therefore, the SIG MCX with the CAT RAT COVERT provides a significantly safer operator blast environment, high / low pressure supersonic and subsonic ammunition combustion comparison notwithstanding. Now consider the subsonic ammunition combustion regime. 8.9-in barrel length MP5 system shooter’s ear Suppression Ratings in the Rankings range from mid-30s with the Dead Air Wolfman (6.182) to just over 50 with the CAT MOB (6.148). The 6.75-in MCX system with subsonic 300 BLK ammunition brings operator protection to high performance suppressed submachine gun severity levels but with a shorter system length and projectile weights that are at least 30% heavier. An interesting comparative data point is that the SIG SAUER SLH 300TI (6.107) achieved an operator Suppression Rating of 44.4 with the 8-in bolt action rifle. The CAT COVERT system operator protection differential from the SIG SLH 300 Ti is relatively small, even with the addition of ejection port blast and mechanical operation.
PEW Science Research Note 3: As 300 BLK semiautomatic weapon system evaluations continue, the multiple blast load hazards detailed above will be characterized from a variety of systems. It is likely that when certain high flow rate silencers are used with low pressure subsonic 300 BLK cartridge on reciprocating systems, mechanical reliability issues will result. This is a subject of further research. Silencer system designers are encouraged to evaluate their products on weapon systems for which they claim operational capability.
PEW Science Research Note 4: It is extremely important for the reader to understand the Suppression Ratings are computed with free field test data, and are therefore universal when translating the weapon and operator to different environments without reflections. However, when the environment becomes complex with many reflecting surfaces, performance translation of different systems is not yet possible; sound field shapes and particle velocities result in varied blast wave time-of-arrivals, as well as changes of blast load angles of incidence; these variations change amplitude and phase waveform components. As a result of these inevitable environmental complexities, user impressions will vary, as both the shooter and bystander. Nonetheless, hazard reduction efficacy in the free field, as characterized by the Suppression Rating, holds. The Suppression Rating comparisons are the current state-of-the-art, and the most “apples to apples” sound suppression performance comparisons that currently exist. Further research is ongoing.
PEW Science Research Note 5: As in all semiautomatic AR-18 and AR-15 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 93 ms in Figure 3a) 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 AR-18 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 may be 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 7: Note that the muzzle Suppression Rating of the CAT RAT COVERT configuration is 62.1 and the at-ear Suppression Rating is 41.8; different zones on the Suppression Rating Dose Chart. The high early time flow rate (lower early time back pressure) of the RAT COVERT contributes to a less severe ejection port blast signature. Gas blowback to the weapon operator, which is a different hazard than ejection port blast, may be reduced by using the FLOW or Base configuration of the silencer, as evaluated in Section 6.191.3 and Section 6.191.4, respectively.
The signatures measured at the shooter’s ear with the RAT COVERT are presented and analyzed in the full Member Version of this report.
The RAT FLOW configuration is examined in the following section.
6.191.3 CAT RAT FLOW Configuration Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the CAT RAT in the FLOW configuration is shown in Table 2. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. The data acquired 0.15 m (6 in) right of the shooter’s ear is only available to membership supporters of PEW Science and the Silencer Sound Standard. You can support public PEW Science testing, research, and development with a membership, here. State-of-the-art public firearm sound signature testing and research conducted by PEW Science is supported by readers like you.
Table 2. CAT RAT FLOW Configuration Sound Metric Summary
6.191.3.1 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 CAT RAT in the FLOW configuration are shown in Figure 7a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 7b, in early time. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 8a. In Figure 8b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shots 2 and 3.
Fig 7a. CAT RAT FLOW Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Pressure Signature
Fig 7b. CAT RAT FLOW Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Pressure Signature
Fig 8a. CAT RAT FLOW Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Impulse Signature
Fig 8b. CAT RAT FLOW Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Impulse Signature
The use of the FLOW module with the CAT RAT completely changes free field blast propagation behavior when compared to the use of the COVERT module. While the early-time flow rate and initial conditions in the Base module remain the same, downstream blast load management is modified and late-time flow rate is elevated. This results in the following behavioral changes, observed in the above data plots:
More expedient blowdown, with ground reflection beginning to decouple (Fig. 7a).
Earlier FRP divergence and more significant negative phase than the COVERT configuration (Fig. 7b).
Faster rise to maximum positive phase blast load impulse (lower Omega Metric) in all shots (Fig. 8a).
Post-FRP blast impulse accumulation initial rate change (Fig. 8b).
Interestingly, the FRP divergence observed in (2) has a momentum rise that is very similar to subsequent shots; due to this behavior, as well as the relatively short duration of positive phase impulse differential, the FRP in the CAT FLOW configuration is effectively masked to bystanders with regard to adverse effects. The signature is detectably different during the first shot, but it is not postulated to induce and elevated risk potential in the free field. Another interesting observation is the shape of the blast momentum accumulation in impulse space (Fig. 8a). The rise time is expedient per (3), but the accumulation is still gradual in early time. Even during FRP, this early accumulation is gradual, though the pressure stages result in distinct but minute intermediate plateaus (~31.25 ms and ~31.37 ms, Fig. 8b).
PEW Science Research Note 10: Functionality of the CAT RAT is now changed; use of the FLOW module transforms the silencer from a low-alpha, moderate-omega hybrid to a low-alpha, low-omega hybrid. Similar functionality change is observed in some other hybrid silencer designs that exhibit modular functionality, such as the Otter Creek Labs Infinity (6.179). However, the Infinity makes this transformation in the supersonic ammunition, high pressure combustion regime and only with an end cap change. When the Infinity is changed and it transitions behaviors, some erratic combustion propagation can result. The Infinity’s adaptation to vary its late time flow rate is more primitive than the RAT’s by necessity; only the end cap can be changed. The Infinity’s internal geometry does vary functionality with the end cap change, more so than would be the case with a conventional silencer, but it is limited nonetheless. The CAT RAT’s full end module change from COVERT to FLOW changes the nature of pressure staging and downstream momentum control. One key differentiator of the CAT RAT FLOW system is its consistency. While there are some phase anomalies in impulse space (~31.5 ms onset, Shot 2 and Shot 3, Fig. 8b), they are confined to peak accumulation in a tight time window. This unusual consistency, from shot to shot, with a distal multi-vent array, is notable especially with low pressure subsonic ammunition. Low pressure propagation consistency is typically a challenge for high flow rate designs. Even high pressure propagation can be difficult to control with distal venting, e.g. HUXWRX FLOW 556 Ti, 10.3-in MK18 (6.168).
PEW Science Research Note 11: The muzzle (bystander) Suppression Rating drops from 62.1 in the COVERT configuration to 46.2 in the FLOW configuration; a difference of almost two full categories. This increase in free field hazard is largely due to the higher amplitude blast overpressure and its more expedient onset as described in (3) above. However, the shooter’s ear (operator) Suppression Rating only decreases from 41.8 to 40.3; an effectively nominal change. This small reduction in operator hazard, despite more significant hazard differential adjacent to the weapon muzzle, is due to pressure field shape and elevated flow rate. The further reduction in back pressure with the FLOW module lowers ejection port blast load enough, in combination with the shorter duration muzzle blast vent pulse, to effectively compensate for the higher muzzle blast amplitude. However, as with all high flow rate systems, care must be taken near reflecting surfaces outside of the free field. When absolute discrete operation is needed, the COVERT module is recommended. The FLOW module is to be used for training purposes and other use cases where high(er) volume fire may be required due to its reduced propensity to induce gas blowback from the weapon system.
As a point of comparison, the 46.2 muzzle Suppression Rating from the CAT RAT FLOW on the 6.75-in MCX is nominally lower than the 47.5 of the Q Half Nelson (6.29) on the 8-in bolt-action. The RAT FLOW has significantly higher early and late-time flow rate than the relatively high back pressure Half Nelson, is smaller in diameter than the Half Nelson, and controls FRP in a superior fashion.
Signature analysis of test data acquired near the operator’s head with the CAT RAT FLOW is presented and analyzed in the full Member Version of this report.
The evaluation in this section covered the performance of the silencer with high early-time flow rate and elevated late-time flow rate. By removing the end module and using only the Base module, late-time flow rate is even further elevated; the blast load is now able to significantly vent from the silencer system. Test results and analysis of the 3.75-in (mount included) Base configuration of the CAT RAT are presented in the following section.
6.191.4 CAT RAT Base Configuration Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the CAT RAT in the Base configuration is shown in Table 3. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. The data acquired 0.15 m (6 in) right of the shooter’s ear is only available to membership supporters of PEW Science and the Silencer Sound Standard. You can support public PEW Science testing, research, and development with a membership, here. State-of-the-art public firearm sound signature testing and research conducted by PEW Science is supported by readers like you.
Table 3. CAT RAT Base Configuration Sound Metric Summary
6.179.4.1 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 CAT RAT in the Base configuration are shown in Figure 11a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 11b, in early time. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 12a. In Figure 12b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shots 2 and 3.
Fig 11a. CAT RAT Base Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Pressure Signature
Fig 11b. CAT RAT Base Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Pressure Signature
Fig 12a. CAT RAT Base Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Impulse Signature
Fig 12b. CAT RAT Base Configuration subsonic 300 BLK SIG MCX AR-18 Semiautomatic Rifle Muzzle Sound Impulse Signature
The CAT RAT Base configuration can be considered a “micro” silencer intended strictly for close quarters operation in which weapon size package is a critical requirement. As such, it is only 3.75-in long from muzzle device shoulder to the end of the distal male threaded coupler. The primary body of the RAT Base module is only 3.25-in long, mount included.
Forgoing the use of either the COVERT or FLOW module extensions with the RAT Base results in more severe blast load propagation. The signatures are more severe, which can be seen by inspection in the above test data. However, what may be unintuitive to the reader is that the combustion propagation from the RAT Base is still relatively controlled. The following behavior is observed in the test data:
Significantly higher peak positive phase blast load amplitude is produced in the free field (Fig. 11a).
There still exists distinct separation between initial coupled jetting and the primary muzzle blast jet (Fig. 11b).
FRP divergence is now more of an issue, compared with the use of the extensions. The divergence occurs much earlier in time, as the A-PULSE technology is shortened. This presents with an earlier coupled jet and more intense primary blast shock (Fig. 11b).
Subsequent blast momentum accumulation in the free field is elevated during FRP (Fig. 12a) but still controlled post-FRP throughout the shot string. Primary vent durations are exceedingly short (see decoupled ground reflection in Fig. 11a, as well as expedient momentum decrease, Fig. 12a).
The combination of (1), (3), and (4) does increase hazard when compared to the longer configurations of the RAT. However, when compared with unsuppressed muzzle blast, the risk is significantly reduced. The 6.75-in test host is not designed to be fired unsuppressed. For reference of unsuppressed subsonic 300 BLK muzzle blast severity, the reader is encouraged to examine Figure 2a in Public Research Supplement 6.127. When blast load waveforms begin to approach the same general shape and are characterized by simple shocks of similar duration, absolute positive phase amplitude can provide useful comparative analysis. For example, from an 8-in barrel, the subsonic test ammunition produces a primary shock amplitude of over 165 dB (close to 4,000 Pa). The average peak blast overpressure from the CAT RAT Base on the 6.75-in system is less than a quarter of that amplitude. Unsuppressed small arms are hazardous regardless of the user’s choice of supersonic and subsonic ammunition. This is particularly the case for confined areas and environments in which the short barrel SIG SAUER MCX variants are fielded. This is the primary design intent of the CAT RAT Base and why it is able to be fielded separately from the extension modules as a standalone unit.
PEW Science Research Note 14: It is somewhat unusual for systems of this length to produce such consistent blast propagation. The CAT RAT Base module delays early venting as discussed in Section 6.191.2.1, but does have annular utilization along with initial pressure staging. This allows it to be somewhat efficient for its “micro” size. There is a significant increase in late time blast momentum propagation rate (significant Omega metric drop) as characterized by the steep initial slope in Figure 12a. This Omega drop does not significantly influence weapon system kinematics because early time flow rate is held constant from the other configurations as part of the A-PULSE technology that originates in the Base module. This allows the 6.75-in SIG MCX system to maintain reliable function even when only the Base module is used.
Blast load propagation at the operator’s head with the CAT RAT Base is examined in the full Member Version of this report.
Comprehensive comparison summary of the three RAT configurations is provided below.
6.191.5 Suppression Rating Comparison (Subsonic 300 BLK from the SIG MCX)
Figure 15 presents a comparison of the PEW Science Suppression Rating of the CAT RAT system in three different configurations on the 6.75-in barrel SIG SAUER MCX 300 BLK weapon system, as previously presented in Section 6.191.1.2. Gas system parameter measurements of the 6.75-in SIG SAUER MCX system are presented on the PEW Science Small Arms Technical Data page. Please note the specific gas system setting used in the tests
Figure 15. Suppression Rating Comparisons of the CAT RAT configurations, Using PEW-SOFT 300 BLK Subsonic SIG MCX AR-18 Test Data and PEW Science Analysis
Figure 15 presents an overall summary of the postulated hazards to the operator and bystanders when fielding the CAT RAT in multiple configurations on the 6.75-in 300 BLK SIG SAUER MCX weapon system, in the free field. Hazards are expressed with the Suppression Rating; a holistic parameter that captures human inner ear damage risk potential from a measured impulsive complex blast 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. Due to its true free field test data origin and complete waveform analytical calculation basis, it is the only known universal suppressed weapon system signature comparison metric available.
As previously discussed, function of the 300 BLK system is intended to be maintained regardless of CAT RAT configuration used. The only system adjustments that should be needed when using the CAT RAT in any configuration with the SIG MCX system are:
If using supersonic 300 BLK ammunition, the “-” gas valve setting is permitted and recommended.
If using subsonic 300 BLK ammunition, the “+” gas valve setting is mandatory.
The "+” setting of the F03 gas valve was used to generate all presented test data in this report. Technical performance comparisons of the three different CAT RAT configurations evaluated are repeated here:
RAT Base: This configuration provides the most compact and lightest weapon system configuration while still significantly reducing blast overpressure hazard to the operator and bystanders when compared to an unsuppressed system. The length and weight are 3.75-in / 9 oz with mount. It is intended for vehicle operations and other environments in which the smallest weapon package is required. Early-time blast load impulse accumulation (alpha parameter) is low. Late-time gas momentum restriction (PEW Science Omega Metric) is also low. Gas blowback to which the operator is subjected is therefore low.
RAT FLOW: This configuration provides a balance of blast overpressure protection (PEW Science Suppression Rating), low gas blowback, and overall signature suppression performance, in the longest and heaviest envelope; 7.75-in / 15.2 oz with mount. It is intended for training operations and/or high-volume fire. Early-time blast load impulse accumulation remains unchanged from the Base configuration. Late-time gas momentum restriction (PEW Science Omega Metric) is increased, but gas blowback to the operator remains low.
RAT COVERT: This configuration provides the highest degree of overall signature suppression performance in the 2nd-longest and heaviest envelope; 7.66-in / 14.7 oz with mount. It is intended for discrete operations. Early-time blast load impulse accumulation remains unchanged from the Base configuration. Late-time gas momentum restriction (PEW Science Omega Metric) increases to maximum. However, operator blast overpressure protection (shooter’s ear Suppression Rating) nominally increases when compared to the FLOW configuration, as reduced muzzle blast loads more than compensate for the elevated omega state. Gas blowback during rapid fire will be elevated, when compared to the other two configurations.
Bystander Protection: Free field blast hazards adjacent to the weapon system are compared below:
The CAT RAT COVERT configuration produces a 62.1 muzzle (bystander) Suppression Rating on this system, which considers internal blast propagation, distal orifice blast pressure propagation, ejection port blast propagation, and weapon system mechanical operation. If the reader is to compare a performance analog in subsonic 300 BLK combustion suppression from the existing pedigree to date, a similar muzzle Suppression Rating of 63.8 was obtained by the Resilient Suppressors Jolene (6.138) on the 8-in barrel bolt-action test platform (no ejection port blast and no mechanical operation other than the trigger actuation and firing pin drop). With its direct-thread mount, the Jolene is 9.1-in long compared with the 7.66-in long RAT COVERT. The RAT also has an exceedingly higher flow rate than the Jolene, as well as significantly more robust FRP suppression. The Otter Creek Hydrogen-L (6.94) and SIG SAUER SRD762TI-QD (6.39) achieve a 65.1 muzzle Suppression Rating on an 8-in barrel bolt-action rifle. Both of those silencers are larger and possess significantly lower early time flow rate than the CAT RAT COVERT. With lower early time flow rate, ejection port blast hazards on semiautomatic platforms increase.
The CAT RAT FLOW configuration produces a muzzle Suppression Rating is 46.2. This level of protection is, on average, between 8-in bolt-action subsonic 300 BLK protection levels of a Q Half Nelson (6.29) and an Energetic Armament VOX S (6.25), which both have higher back pressure than the RAT FLOW and both lack FRP control. The level of protection is also similar to that of a HUXWRX CASH 9K on an MP5 (6.97) and approaching that of the Diligent Defense Enticer-S (6.89).
The CAT RAT Base configuration produces a muzzle Suppression Rating of 21.6. That level of protection is, on average, similar to bystander hazard mitigation from a Surefire SOCOM762-RC2 on a 5.56 MK18 (6.73).
Operator Protection: Free field blast hazards to which the operator is subjected are compared below:
The CAT RAT COVERT configuration produces a 41.8 operator Suppression Rating on this system, in the free field. As more test records are populated with subsonic 300 BLK combustion from semiautomatic systems, comparison points will be generated. For now, the reader may consider the differential between an operator Suppression Rating in the 40-zone and an operator Suppression Rating for the entire semiautomatic dataset to date, including both supersonic 5.56x45mm NATO combustion, and subsonic 9x19mm combustion, omitting subsonic .22LR rimfire. The highest shooter’s ear Suppression Rating published on a standard untuned 5.56 semiautomatic rifle is 32.4 from the low back pressure HUXWRX FLOW 556 Ti (6.167). A high back pressure silencer, the Maxim Defense DSX, achieved a 32.5 shooter’s ear Suppression Rating on the tuned SURG system (6.111) and only 22.0 on the standard untuned system (6.110). Therefore, the SIG MCX with the CAT RAT COVERT provides a significantly safer operator blast environment, high / low pressure supersonic and subsonic ammunition combustion comparison notwithstanding. Now consider the subsonic ammunition combustion regime. 8.9-in barrel length MP5 system shooter’s ear Suppression Ratings in the Rankings range from mid-30s with the Dead Air Wolfman (6.182) to just over 50 with the CAT MOB (6.148). The 6.75-in MCX system with subsonic 300 BLK ammunition brings operator protection to high performance suppressed submachine gun severity levels but with a shorter system length and projectile weights that are at least 30% heavier. An interesting comparative data point is that the SIG SAUER SLH 300TI (6.107) achieved an operator Suppression Rating of 44.4 with the 8-in bolt action rifle. The CAT COVERT system operator protection differential from the SIG SLH 300 Ti is relatively small, even with the addition of ejection port blast and mechanical operation.
The CAT RAT FLOW configuration produces a 40.6 operator Suppression Rating on this system, in the free field. This is very similar to the gross level of operator protection with the Base configuration. However, outside the free field environment, the FLOW configuration may induce more severe blast load reflections than the COVERT configuration, which will impact both shooter’s ear (operator) and muzzle (bystander) Suppression Rating metrics.
The CAT RAT Base configuration produces a 22.7 operator Suppression Rating on this system, in the free field. This is, essentially, close to the median operator protection level of a suppressed 5.56x45mm NATO 10.3-in barrel MK18 weapon system. The primary body of the Base configuration is only 3.25-in long, with mount. The previous generation KAC 5.56 QDC silencer on the MK18 (6.104) has an identical operator Suppression Rating. Also comparable are the Liberty Precision Machine Torch (6.126) on the MK18 and Surefire SOCOM556-RC3 on the MK18 (6.151) at 22.4.
The above bystander and operator personnel hazard comparisons are only possible with the PEW Science Suppression Rating, as the blast overpressure histories from all of these systems differ significantly in shape, duration, phase, and frequency components.
Signature at the operator’s head is a function of both muzzle and ejection port signatures from reciprocating weapon systems like the SIG SAUER MCX AR-18.
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.
6.191.6 Review Summary: Combat Application Technologies CAT/RAT on a 300 BLK SIG SAUER MCX Virtus TACOPS with 6.75-in Barrel
When paired with the 6.75-in barrel SIG MCX and fired with Discreet Ballistics 190gr 300 BLK subsonic ammunition, the CAT RAT in the COVERT configuration achieved a Suppression Rating™ of 62.2 in PEW Science testing. In the FLOW configuration, the CAT RAT achieved a Suppression Rating of 47.6. The CAT RAT Base configuration with no extensions achieved a Suppression Rating of 25.6.
As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Laboratory Staff Opinion:
The Combat Applications Technology CAT/RAT is a multi-unit modular silencer system intended to suppress 300 BLK personal defense weapons (PDWs). Its advanced hybrid technology, fully adaptable performance, and specialized design for the SIG SAUER MCX family of systems, makes it one of the most unique examples of high performance suppressed small arm system optimization evaluated by the PEW Science Laboratory, to date. The end user may choose to field the CAT RAT in covert operations, high volume fire training scenarios, or close quarter vehicle environments and not sacrifice weapon system reliability. The CAT RAT is capable of suppressing both subsonic and supersonic 300 BLK from the complete range of MCX and Rattler system barrel lengths, as well from other 300 BLK systems.
The CAT RAT system was developed to address issues with suppressing the SIG SAUER MCX and Rattler family of 300 BLK PDWs. By only following the SIG SAUER guidance of “+” gas system setting for subsonic 300 BLK ammunition and “-” gas system setting for supersonic 300 BLK ammunition, all three configurations of the CAT RAT system provide reliable weapon function with a large variety of ammunition types and projectile weights, on all SIG 300 BLK barrel lengths. Several silencers do not. The SIG SAUER 300 BLK MCX AR-18 derivative systems, if properly suppressed, offer users high reliability and low signature potential. In contrast with AR-15 systems, AR-18 system adaptation specific to the 300 BLK SIG MCX has less blast overpressure emitting sources, as well as a more compact recoil system enabling native folding stock use.
The CAT RAT system is modular not in “end cap” change but in complete adaptation using CAT A-PULSE technology, which is a modular adaptation of SB-SHOCK and SNIPER2. The Base RAT configuration effectively modulates the alpha state not to drop below a critical value by delaying early venting more than typical through an increase in initial shock pulse clearing time. Tuned for the MCX system, this allows A-PULSE to manage early-time flow rate consistently regardless of downstream blast momentum propagation, which is a key design parameter for the SIG MCX system. And, because the COVERT and FLOW extensions are truly downstream modules, A-PULSE functions with both subsonic and supersonic 300 BLK ammunition, regardless of the RAT configuration chosen by the user.
RAT Base: This configuration provides the most compact and lightest weapon system configuration while still significantly reducing blast overpressure hazard to the operator and bystanders when compared to an unsuppressed system. The length and weight are 3.75-in / 9 oz with mount. It is intended for vehicle operations and other environments in which the smallest weapon package is required. Early-time blast load impulse accumulation (alpha parameter) is low. Late-time gas momentum restriction (PEW Science Omega Metric) is also low. Gas blowback to which the operator is subjected is therefore low.
RAT FLOW: This configuration provides a balance of blast overpressure protection (PEW Science Suppression Rating), low gas blowback, and overall signature suppression performance, in the longest and heaviest envelope; 7.75-in / 15.2 oz with mount. It is intended for training operations and/or high-volume fire. Early-time blast load impulse accumulation remains unchanged from the Base configuration. Late-time gas momentum restriction (PEW Science Omega Metric) is increased, but gas blowback to the operator remains low.
RAT COVERT: This configuration provides the highest degree of overall signature suppression performance in the 2nd-longest and heaviest envelope; 7.66-in / 14.7 oz with mount. It is intended for discrete operations. Early-time blast load impulse accumulation remains unchanged from the Base configuration. Late-time gas momentum restriction (PEW Science Omega Metric) increases to maximum. However, operator blast overpressure protection (shooter’s ear Suppression Rating) nominally increases when compared to the FLOW configuration, as reduced muzzle blast loads more than compensate for the elevated omega state. Gas blowback during rapid fire will be elevated, when compared to the other two configurations.
The CAT RAT system is offered in different retail packages; it is intended to be used with the included AI NANO muzzle devices which possesses LH threading that interfaces with the proximal end of the Base module. The COVERT and FLOW modules possess LH threading which interfaces with the distal end of the Base module.
Each module is DMLS (3D printed) from a proprietary titanium alloy. The PEW Science laboratory has not performed exhaustive durability testing on the RAT system, but in limited trials, no adverse effects were observed during the firing of several back-to-back magazines with both supersonic and subsonic 300 BLK ammunition from the 6.75-in barrel SIG system. As always, durability limitations exist for all silencers and are a function of barrel length, ammunition type, and firing schedule. PEW Science encourages the end user to contact the manufacturer for guidance regarding firing schedule limitations. Note that AI NANO muzzle devices do induce side-wall blast load impingement in the first expansion chamber of the Base module, and that wall is reinforced. Use of other muzzle devices with the CAT RAT system has not been evaluated by PEW Science. Performance differentials in signature suppression and durability may occur.
In this review, the CAT RAT system performance metrics depend upon suppressing a subsonic intermediate rifle cartridge on a short barrel gas-operated rifle, which is an incredibly difficult task. While the sound signature of such cartridges can be suppressed to levels that may result in the desire of the shooter and bystanders to not wear hearing protection, PEW Science encourages the reader to remain vigilant with regard to all subsonic rifle cartridge suppression claims. The gas volume and combustion products created by firing a subsonic intermediate rifle cartridge such as 300 BLK are still 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 subsonic rifle use is not insignificant. PEW Science encourages the reader to consider the Suppression Rating when deciding on an appropriate silencer and host weapon combination for their desired use.
