SSS.6.217 - Combat Application Technologies CAT/ST and the M4A1 Mid-Gas 5.56x45mm 14.5-in Barrel Automatic AR15 Rifle
/Combat Application Technologies CAT/ST on the M4A1 Mid-Gas 5.56x45mm AR15 with 14.5-in Barrel
The CAT/ST (“ST” in this report) is designed by Combat Application Technologies (CAT). It is a .223 caliber centerfire rifle silencer, intended to suppress the 5.56x45mm NATO cartridge on reciprocating weapons with barrel lengths of 10.3 inches and longer. It has a 1.6-inch diameter and the silencer core is 6.3 inches long. The included AI NANO QD mount has wrench flats that increase the total system length to 6.59 inches. The silencer is also available in a HUB compatible version with 1.375-24 tpi rear mount threading which is shorter with no mount installed. The CAT ST silencer is DMLS (3D-printed) from a proprietary Inconel alloy and is also available in a titanium model. The core of the Inconel QD version of the silencer weighs 18.1 ounces and the 1/2-28tpi AI NANO mount weighs 2.4 ounces, for a total system weight of 20.5 ounces, as tested. The CAT ST can be obtained at Silencer Shop.
Silencer Hazard Map:
The predicted personnel hazards generated by the tested weapon systems in this report, in the free field, are shown in the adjacent Silencer Hazard Map. Click or tap the Map to enlarge. Please reference Silencer Hazard Map Brief 8.1.14 for further details. The PEW-SOFT HD Blast Hazard Prediction Tool and Hazard Mapper is presented in Report 8.1.1.
CAT ST 14.5-in M4A1 AR-15 Free Field Hazard Map Produced by PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
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-154-001-26. Therefore, data pertaining to the CAT/ST 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 ST on the M4A1 Mid-Gas Automatic AR-15 rifle, chambered in 5.56x45mm NATO with a 14.5-inch barrel. Federal XM193 55gr ammunition was used in the test. The standard PEW Science M4A1 test host weapon system is described in Public Research Supplement 6.127.
Report Table of Contents:
Section 6.217.1 contains an abbreviated overall summary of CAT ST 5.56 rifle silencer performance on the 14.5-in M4.
Section 6.217.2 contains CAT ST test results and analysis.
Section 6.217.3 contains overall Suppression Rating comparisons of the CAT ST with other rifle silencers on the current market on the M4A1 Mid-Gas Rifle, including various configurations of the Otter Creek Labs OCM5 and OCM6, Whiskey Quebec 5.56 Purged and Non-Purged, Wolfpack Armory Disruptor 556, Otter Creek Labs Infinity, Dillon DRC556, CAT TSWIF, Sylvan Arms SA223TIS, BOE Mod 1, Echo Zulu Defense X1R556-Ti, PTR VENT Spiritus 556i, HUXWRX FLOW 556 Ti, Surefire SOCOM556-MINI2, KAC QDC/CRS-PRT, KAC QDC/MCQ-PRT, CAT/WB/A1, and Surefire SOCOM556-RC2.
Section 6.217.4 contains an article summary and PEW Science laboratory staff opinions.
Summary: When paired with the 14.5-in barrel M4A1 and fired with Federal XM193 mounted with the AI NANO, the Combat Application Technologies CAT ST achieved a Suppression Rating™ of 53.7 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.
6.217.1 CAT 5.56 Silencer Automatic Rifle Suppression Performance Summary
The PEW Science Silencer Sound Standard includes the 5.56x45mm NATO evaluation of several rifle silencers designed and manufactured by Combat Application Technologies. Comprehensive performance Rankings are tabulated in Section 7 of the Standard. This report examines the performance of the universal 5.56 model, the CAT ST. The scope of this report contains standard untuned 14.5-in M4A1 weapon system combustion suppression analysis of the silencer.
Figure 1 presents a gross performance comparison of three CAT 5.56 silencers on the M4A1 with the unsuppressed case. The CAT WB (6.130) uses a strict implementation of CAT SURGE BYPASS technology, whereas the CAT TSWIF (6.193) uses some elements of the same, adopted for its modular use with different blast diverters. The CAT ST uses an updated technology named CAT SBX, detailed in the next section of this report.
Figure 1. Suppression Rating Comparisons of CAT 5.56 Rifle Silencers Using PEW-SOFT 5.56x45mm Supersonic M4A1 Test Data and PEW Science Analysis
From the above semiautomatic short-barrel AR-15 rifle performance metrics, it can be concluded that even with silencers from the same manufacturer, signature suppression levels may increase or decrease in accordance with silencer internal design.
All three of these CAT 5.56 rifle silencers are classified as hybrid designs in the research taxonomy. It is very interesting to note that the previous generation CAT WB is a relatively compact “utility” silencer for 5.56 weapons and the SURGE BYPASS technology’s high gross flow rate enables high(er) shooter’s ear (operator) Suppression Ratings on standard untuned host weapons like the M4 rifle examined herein, and the previously evaluated 10.3-in MK18 (6.129). The CAT ST exhibits significantly different behavior than the CAT WB on the 14.5-in M4; the muzzle (bystander) Suppression Rating is over a category higher than that of the WB, and the operator Suppression Rating almost a category lower. When using the 10.3-in MK18, with its smaller gas port size and significantly shorter barrel and dwell time, the pure muzzle suppression performance of the CAT ST is reduced, but its shooter’s ear (operator) protection increases and approaches (and almost mirrors) that of the WB on that weapon. The CAT ST with its SBX technology is designed for pure muzzle suppression scaling across all common barrel lengths. Users concerned with localized free field operator hazard from ejection port blast are encouraged to tune their weapon systems. This may be intuitive given the shooter’s ear Suppression Rating of the CAT ST on the 14.5-in standard untuned M4 shown in the above figure. The early-time flow rate in the CAT ST is relatively high, and its late time flow rate is throttled. Therefore, “gas blow back” is still reduced compared to typical (conventional) rifle silencers.
Due to the extremely high degree of muzzle suppression performance from the CAT ST, users may perceive overall signature to be less severe than with some other suppressed rifle systems. Nonetheless, users are encouraged to be mindful of acute localized hazards from ejection port blast loads and consider the operator hazards characterized by the shooter’s ear Suppression Rating, while keeping in mind that gas system characteristics of a rifle may significantly influence operator protection. This is particularly the case with the CAT ST as muzzle blast is significantly suppressed throughout the risk field.
The detailed 5.56x45mm NATO 14.5-in M4A1 evaluation of the CAT ST rifle silencer follows.
6.217.2 CAT ST Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the CAT ST 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. CAT ST Sound Metric Summary
6.217.2.1 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 ST are shown in Figure 2a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 1b, in early time. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 3a. In Figure 3b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shots 2 and 3.
Fig 2a. CAT ST 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Pressure Signature
Fig 2b. CAT ST 5.56x45mm NATO M4A1 Automatic Rifle Sound Pressure Signature
Figure 3a. CAT ST 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature
Figure 3b. CAT ST 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature
The Combat Application Technologies CAT ST is designed for pure muzzle suppression scaling across all common barrel lengths. It is considered to be a full-size 5.56 rifle silencer, as its length with mount is approximately 6.6 inches, as tested. Some modern hybrid designs require significant blast load pressure input amplitude to maintain suppression efficiency. This behavior, which may be counterintuitive to the reader, is a result of complex internal geometries and staged designs that do not allow full internal surface area exposure to expanding combustion gasses below a certain pressure threshold. However, the SBX technology in the CAT ST does not exhibit the same behavior. As barrel length decreases, the muzzle Suppression Rating from the silencer will drop. As barrel length increases, the Suppression Rating will increase. This is similar to the predictable gross behavior of most legacy and conventional silencer designs.
PEW Science Research Note 1: For an an example of a high performance silencer that loses suppression performance with barrel length increase, the reader is referred to the examination of the shorter Stealth Additive Works Tisha (6.209) on the 10.3-in MK18. Additional testing has been performed of both the Tisha and the ST on other systems that is not yet published. Whereas the Tisha will outperform the CAT ST in pure suppression performance on the 10.3-in weapon system by a few points, the ST outperforms the Tisha as the barrel length increases. The CAT ST outperforms the Tisha on the 14.5-in M4 by over half a Suppression Rating category. PEW Science forecasts that these unintuitive performance realities will continue to occur as 3D printing enables silencer designers to implement additional complexities in silencer systems. Whether these performance outcomes are purposeful or not is largely irrelevant. It is important that entities performing characterization and/or the manufacturers advise end users of these performance outcomes.
The overall design of the CAT ST, utilizing the SBX technology, produces relatively unusual signatures on the tested host weapon system. Observations from the above test data include the following:
Blast load amplitude is significantly suppressed. After coupled bullet Mach wave and precursor jetting, primary jet onset is reduced to unusually low amplitudes (Fig. 2).
Bolt carrier group (BCG) return to battery occurs more slowly than typical (Fig. 2a).
Blast load momentum experiences delayed ramping, and ramping decay in first-round-pop (FRP), with FRP accumulation ending prior to subsequent shot accumulations (Fig. 3).
Jetting is highly controlled with extremely low impulse amplitude (Fig. 3).
The observations in (1) are somewhat expected given SBX’s distal momentum control. However, momentum throttle occurring over the entire duration of primary accumulation (3), to this degree, is highly unusual. And despite the relatively low shooter’s ear Suppression Rating (signature evaluation provided later in this report), the BCG speed (2) is relatively slow. Given these performance characteristics, coupled with the observation in (4), it can be concluded that the CAT ST produces a free field blast signature that is not only indicative of advanced suppression, but different than any other examined in the research, to date. Further evaluations are needed for full characterization. As of the time of this report, the CAT ST produces the highest levels of pure 5.56 NATO suppression performance tested.
The CAT ST does produce higher levels of FRP than some other CAT rifle silencers. This is relative to the CAT ST itself, when compared to other shots in the suppressed fire string. Regardless of intensity, its FRP is still less severe than all shots from the other silencers.
PEW Science Research Note 2: The unusual signature suppression behavior from the CAT ST may be characterized, in simple terms, as “relatively high early-time flow and efficient late time throttling.” The SBX technology in the ST differs from SURGE BYPASS in that the ST possesses less early vent path utilization and more advanced distal end pressure staging. On “over-gassed” rifle hosts, like the standard untuned M4 used in this test program, its overall flow rate is not high enough to reduce adverse ejection port blast to low levels like a Flow Through silencer, such as those manufactured by HUXWRX. However, with any degree of weapon system tuning, or even dwell time decreases or port size reductions, operator hazard drops significantly. An overall performance conclusion is that the blast momentum propagation from the CAT ST is so controlled and low amplitude, and its early time flow rate is high enough, that the likelihood of its gross suppression performance being eclipsed by other 5.56 silencers in the research is low, with any degree of weapon tuning. For a visual illustration of spatial hazards, consider the Silencer Hazard Map at the beginning of this report and presented in Silencer Hazard Map Brief 8.1.14. The “red” zone on the map displayed around the ejection port of the weapon system will be lowered in intensity as gas system parameters vary. For a quantitative example of such hazard reduction from a gas port size change, the reader is encouraged to examine the case study of the Maxim Defense DSX SURG (6.111) in which the gas port orifice diameter was varied from 0.070-in to an effective 0.053-in on a 10.3-in MK18 system. The shooter’s ear (operator) Suppression Rating on that 10.3-in weapon system changed from 22.0 to 32.5 (a full category) solely due to reduced ejection port blast. Exact hazard reduction improvements will vary for each weapon system. As discussed in the summary in the first section of this report, the CAT ST on the MK18 produces a similar shooter’s ear Suppression Rating to that of a CAT WB on a MK18. If “tuning” a MK18 for both the ST and the WB, it is likely that the resulting shooter’s ear Suppression Rating on the ST system would be higher than that on the WB system. However, the relationship on the M4 may not scale linearly. These nonlinearities in hazard scaling should be expected by users across weapon systems. While the existence of personnel hazard reduction from weapon tuning is easily predictable, quantifiable metrics are not, without further study.
PEW Science Research Note 3: Blast loads are produced by dynamic events and resulting overpressure varies with time and distance from origin. As incident blast overpressure waves expand in air, they transfer momentum. The momentum transfer potential of the waves is called impulse (please reference Silencer Sound Standard Section 2). The impulse history at the MIL-STD measurement location (1.0 m left of the silencer end cap) from the CAT ST on the M4 weapon system is shown in Figure 3. While hazards depend on both pressure and impulse, as well as on waveshape and frequency components, it is important to highlight that the momentum transfer behavior displayed in Figure 3 is highly unusual. The CAT ST limits blast momentum propagation to levels that are approximately 70% lower, in absolute amplitude, than from silencers like the PTR VENT Spiritus 556i (6.156) on the same weapon system. While this does not mean the CAT ST is “70% quieter” than the VENT Spiritus, it does mean that human risk adjacent to the end of both silencers on this weapon system is significantly different. This is reflected in their muzzle (bystander) Suppression Ratings: 44.0 (PTR VENT Spiritus) vs. 53.7 (CAT ST). This category level jump in suppression performance, even with the 0.3-in length increase of the CAT ST, sets a new performance benchmark in the research pedigree.
PEW Science Research Note 4: 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. Although contrasted with so-called Flow-Through technologies in the research taxonomy, hybrid designs predate OSS (HUXWRX) designs. 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, 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.
PEW Science Research Note 5: As silencer technology continues to advance, size and weight refinements made possible by increased design efficiencies occur. As discussed in Research Note 3, the CAT ST significantly outperforms the VENT Spiritus in pure suppression performance on this host weapon, and is slightly longer. The previously evaluated BOD MOD 1 (6.183) matches the muzzle Suppression Rating of the Spiritus, but is much larger than both the Spiritus and the ST, with a diameter of 1.75 inches and a 7.7-inch length, as tested. That may be considered by users to be a different size class of silencer. The Dillon DRC556 (6.194) also exhibits pure muzzle suppression performance on par with that of the PTR and BOD (C-Products Defense) silencers, and is only 5.75 inches long, as tested. The visualization tool scatter plot in the Member Rankings Section may assist the reader with such comparisons, as the tool allows silencer hazard data to be filtered by both tested system length and weight.
PEW Science Research Note 6: 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 7: 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 90 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 8: The closing time of the AR15 bolt is directly related to the flow restriction of a silencer for a given weapon system. PEW Science has determined bolt closing time variation from the unsuppressed state to be a reliable indicator of silencer back pressure, with strong correlation with the PEW Science Back Pressure Metric, Omega and the alpha parameter. However, PEW Science has also determined that the indicator 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 entire signatures are used in analysis and Suppression Rating calculations.
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 9: Note that the muzzle Suppression Rating of the Combat Application Technologies CAT ST is 53.7 and the at-ear Suppression Rating is 20.8; considerably different zones on the Suppression Rating Dose Chart. The higher back pressure of the CAT ST relative to some other CAT models and the “over gassed” nature of the rifle contributes to severe ejection port blast signature when compared to lower back pressure silencers on the standard untuned M4A1 weapon system. System tuning (adjustable gas block or heavier buffer mass) may be required to optimized the user’s particular weapon system. Weapon tuning may influence hazard reduction efficacy, and is outside the scope of this study.
The signatures measured at the shooter’s ear with the CAT ST are presented and analyzed below.
6.217.2.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 6-shot test acquired with PEW-SOFT at the shooter’s ear are shown below. Again, the waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz).
The primary sound signature pressure histories at the ear for all 6 shots are shown in Figure 4. The primary sound signature history is shown in Figure 4a. An annotated timescale is displayed in Figure 4b, for Shots 1 and 2. The real sound impulse (momentum transfer potential) histories at the ear from the same 6-shot test are shown in Figure 5. Again, full and shorter timescales are shown, this time of Shot 1, Shot 2, and Shot 3.
Figure 4a. Otter Creek Labs OCM5 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature
Figure 4b. Otter Creek Labs OCM5 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 5a. Otter Creek Labs OCM5 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature
Figure 5b. Otter Creek Labs OCM5 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature Peaks
The above measured test data from the CAT ST on the M4, near the operator’s head, displays interesting results. Bolt BCG speed (Fig. 4a) and momentum transfer timing (front-loaded FRP; Fig. 5b) display signs of low back pressure silencer behavior. However, blast load amplitude is elevated (Fig. 4b). Furthermore, positive phase duration is, indeed, prolonged (Fig. 4b). In conclusion, the flow rate from the CAT ST is not high enough, in a gross sense, to allow an untuned M4 to behave like it would with, for example, a HUXWRX silencer, a CAT WB, a VENT Spiritus, etc.
PEW Science Research Note 10: The behavior of the CAT ST on the MK18 does not display as significant an operator hazard as on the M4; on the MK18, the system will behave similarly to that of a WB in operator Suppression Rating. However, on the M4 with its longer dwell time and larger gas port, to experience less ejection port hazards with the ST, weapon tuning will be mandatory. This may include changes such as a heavier buffer, reduced gas port orifice size, or both. Heavier buffers enact increased inertial resistance that starts from rest to delay unlock. Reduced gas port orifice sizes reduce gas tube infill pressure amplitude in early time, thus lowering initial internal gas tube impulse accumulation to the carrier and alter both unlock timing and gas tube orifice blast load propagation out of the ejection port. The reader should note that a direct-impingement AR system does expel blast loads from the breech that originate from both the chamber and the gas tube itself. “Gas” means “expanding combustion gasses;” those produce blast overpressure in free air. The “gas” you see expelled from system in videos or photos of AR weapon systems firing is from late time phenomena: particulate ejecta and temperature dependent condensation. The blast loads themselves propagate at the speed of sound in air, similar to those produced by chamber blast and muzzle blast. All waves coalesce during the time regime of interest.
Ejection port blast hazards are not just confined to the AR-15 platform; they may occur in any reciprocating weapon system, including from the HK MP5 submachinegun, combat handguns, and other semiautomatic and automatic platforms.
It should be noted that the total risk field while using a CAT ST vs. a CAT WB is considerably different, regardless of similarities in operator Suppression Rating from weapon tuning. Late time effects will influence operator perception, particularly around reflecting surfaces. The blast impulse control from the ST is very high; this may tempt the operator not to use hearing protection with the weapon system. Acute operator risk from ejection port blast sill holds.
PEW Science Research Note 11: Relative FRP severity to the operator is less significant on the M4 than it is to bystanders with the ST. This is largely due to the large contribution of ejection port blast to operator hazard, relative to the significantly suppressed muzzle blast. FRP is a muzzle blast phenomenon. The risk differential to the operator is driven by the primary risk factor on this system (the ejection port blast).
Below, the CAT ST is compared with other silencers on the standard untuned M4 rifle.
6.216.3 Suppression Rating Comparison (5.56x45mm from the M4A1)
Figure 6 presents a comparison of the PEW Science Suppression Ratings of the CAT ST rifle silencer, with those of several other silencers on the M4A1 weapon system. The standard PEW Science M4A1 test host weapon system is described in Public Research Supplement 6.127.
Figure 6. Suppression Rating Comparisons of the CAT ST, Otter Creek Labs OCM5, OCM6, Whiskey Quebec 5.56 Purged and Non-Purged, Wolfpack Armory Disruptor 556, Infinity, Dillon DRC556, CAT TSWIF, Sylvan Arms SA223TIS, BOE Mod 1, Echo Zulu Defense X1R556-Ti, PTR VENT Spiritus 556i, HUXWRX FLOW 556 Ti, KAC QDC/CRS-PRT, KAC QDC/MCQ-PRT, Surefire SOCOM556-MIN2, CAT WB, and SOCOM556-RC2 with different mounts, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis
Figure 10 presents an overall summary of the postulated hazards to the operator and bystanders when fielding the CAT ST on the M4A1 weapon system (shown in red). Data is also presented for the fielding cases of the Otter Creek Labs OCM5 and OCM6 (6.213), Battle Born Supply Co. Whiskey Quebec 5.56 series (6.206), Wolfpack Armory Disruptor 5.56 (6.199), Otter Creek Labs Infinity (6.196), Dillon DRC556 (6.194), CAT TSWIF (6.193), Sylvan Arms SA223TIS (6.187), BOE Mod 1 (6.183), Echo Zulu Defense X1R556-Ti (6.181), PTR VENT Spiritus 556i (6.176), HUXWRX FLOW 556 Ti (6.168), Surefire SOCOM556-RC2 (6.128), SOCOM556-MINI2 (6.144), and KAC QDC PRT units (6.156) on different muzzle devices, along with fielding of the CAT WB (6.130). Hazards are expressed with the Suppression Rating; a holistic parameter that captures human inner ear damage risk potential from a measured impulsive complex overpressure signature during the entire time regime of weapon operation, including combustion, complete blowdown, and all mechanical operation, including the carrier group returning to battery, in the true free field. The parameter may be used with the dose chart at the beginning of this report. The PEW Science Suppression Rating is a damage risk criterion (DRC), a lower Suppression Rating indicates a higher personnel hazard in the free field - it is not a subjective quantity; it is an objective quantification of hearing damage risk potential. 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.
The following gross conclusions can be made from the above:
The CAT ST produces free field bystander hazard reduction that is higher than all other tested systems, by a significant margin. Other high performance designs like the Dillon DRC556 (6.194), BOE Mod 1 (6.183), and PTR VENT Spiritus 556i (6.176) produce muzzle Suppression Ratings approximately a category lower than the CAT ST. This is a significant finding, particularly because the shooter’s ear (operator) Suppression Rating from the CAT ST on this weapon system is somewhat similar to that from the DRC556.
To restate, the free field operator (shooter) hazard reduction of the CAT ST is somewhat similar to that of the Dillon silencer on this host weapon system, and both exhibit protection lower than typical on the untuned M4A1 rifle. This results in acute hazards that are similar in severity to the SOCOM556-MINI2 with a 3-prong mount (6.144) or SOCOM556-RC2 with a WARCOMP mount (6.128). By inspection, it can be concluded that weapon tuning is advised for this platform. Reduction in gas port impulse by reducing dwell time (the use of a system like a MK18 instead, for example), or by reducing gas port orifice size, will directly decrease operator hazard.
PEW Science Research Note 12: As discussed earlier in this report, the SBX technology in the ST exhibits relatively predictable suppression scaling behavior. As barrel length decreases, the muzzle Suppression Rating from the silencer will drop. As barrel length increases, the Suppression Rating will increase. This is similar to the predictable gross behavior of most legacy and conventional silencer designs; this may be a welcome conclusion for users pursuing high performance advanced hybrid silencers. As a counterintuitive counterexample, the recently evaluated Stealth Additive Works Tisha (6.209) somewhat outperforms the CAT ST on the 10.3-in MK18 in pure suppression performance, but the ST eclipses the Tisha’s performance by over half a category on the 14.5-in M4. Nonlinear and indirectly proportional suppression performance relationships continue to be examined in the research. Further study is ongoing. As of the time of this report, the CAT ST produces the highest levels of pure 5.56 NATO suppression performance tested.
As detailed in this report, signature at the operator’s head is a function of both muzzle and ejection port signatures from the AR-15 weapon system. Specific weapon system parameters will dictate modification efficacy.
Small arm weapon system suppression performance is a spectrum. The PEW Science Suppression Rating and the Silencer Sound Standard help quantify this spectrum for end users and industry, objectively.
6.216.4 Review Summary: Combat Application Technologies CAT ST on the M4A1 Mid-Gas 5.56x45mm AR15 with 14.5-in Barrel
When paired with the 14.5-in barrel M4A1 and fired with Federal XM193 mounted with the AI NANO, the Combat Application Technologies CAT ST achieved a Suppression Rating™ of 53.7 in PEW Science testing.
As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Laboratory Staff Opinion:
The Combat Application Technologies CAT ST is a full-size 5.56 rifle silencer intended for use on all common weapon system barrel lengths. Its suppression performance may be considered “state of the art,” and is extremely high relative to other systems on the current market. There exist no other silencers evaluated by the PEW Science Laboratory, as of the date of this publication, that exhibit the levels of pure suppression performance measured from the CAT ST on the M4 weapon system. Its SBX technology is also used in the CAT AKB 30 caliber rifle silencer. Both silencers are available in both 3D printed Inconel and Titanium models, in both QD or HUB-compatible variants. While the silencer has higher effective back pressure and first-round-pop (FRP) relative to previous generation CAT silencers, its FRP and flow rate performance are still strongly competitive with the rest of the market.
The Combat Application Technologies CAT ST is designed for pure muzzle suppression scaling across all common barrel lengths. It is considered to be a full-size 5.56 rifle silencer, as its length with mount is approximately 6.6 inches, as tested. Some modern hybrid designs require significant blast load pressure input amplitude to maintain suppression efficiency. This behavior, which may be counterintuitive to the reader, is a result of complex internal geometries and staged designs that do not allow full internal surface area exposure to expanding combustion gasses below a certain pressure threshold. The SBX technology in the ST does not exhibit the same behavior. As barrel length decreases, the muzzle Suppression Rating from the silencer will drop. As barrel length increases, the Suppression Rating will increase. This is similar to the predictable gross behavior of most legacy and conventional silencer designs.
The unusual signature suppression behavior from the CAT ST may be characterized, in simple terms, as “relatively high early-time flow and efficient late time throttling.” The SBX technology in the ST differs from SURGE BYPASS in that the ST possesses less early vent path utilization and more advanced distal end pressure staging. On “over-gassed” rifle hosts, like the standard untuned M4 used in this test program, its overall flow rate is not high enough to reduce adverse ejection port blast to low levels like a Flow Through silencer, such as those manufactured by HUXWRX. However, with any degree of weapon system tuning, or even dwell time decreases or port size reductions, operator hazard drops significantly. An overall performance conclusion is that the blast momentum propagation from the CAT ST is so controlled and low amplitude, and its early time flow rate is high enough, that the likelihood of its gross suppression performance being eclipsed by other 5.56 silencers in the research is low, with any degree of weapon tuning.
The CAT ST limits blast momentum propagation to levels that are approximately 70% lower, in absolute amplitude, than from silencers like the PTR VENT Spiritus 556i on the same weapon system. While this does not mean the CAT ST is “70% quieter” than the VENT Spiritus, it does mean that human risk adjacent to the end of both silencers on this weapon system is significantly different. This is reflected in their muzzle (bystander) Suppression Ratings: 44.0 (PTR VENT Spiritus) vs. 53.7 (CAT ST). This category level jump in suppression performance, even with the 0.3-in length increase of the CAT ST, sets a new performance benchmark in the research pedigree.
The user may choose to field either Inconel or titanium versions of the CAT ST, in either HUB or QD compatible models. Durability is a function of use case and the manufacturer should be consulted with regard to firing schedule limitations. The user may adapt the silencer to a variety of mounting systems of their preference if using a HUB model. The tested system was the QD model used with the included AI NANO mount; the use of different mounts may change system performance.
In this review, the CAT ST 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.
