KAC 556 QDC/CRS-PRT and 556 QDC/MCQ-PRT System Optimization with Two Muzzle Devices on Four Hosts

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 for this research program was generated with funding provided by PEW Science members. All KAC system apparatus and specimens were loaned by consumer and corporate members of the Research Cooperative.

6.156.1 Program Scope and Test Specimens

This report summarizes the testing and analysis results of a PEW Science internal research (IR) program characterizing the performance of Pressure Reduction Technology (PRT) silencers produced by Knight’s Armament Company (KAC). Testing was performed with the following 5.56x45mm rifle silencers:

KAC 556 QDC/CRS-PRT [Quick Disconnect / Combat Rifle Suppressor]
KAC 556 QDC/MCQ-PRT [Quick Disconnect / Mini Close Quarters]

Two muzzle devices were used in the test program:

5.56 QDC Flash Eliminator [3-Prong Flash Hider]
5.56 MAMS Muzzle Brake [Multi-Axis Muzzle Stability Brake]

Four host weapon upper receiver groups were used in the test program, on the standard PEW Science laboratory lower receiver assembly with the typical H2 carbine buffer and spring assembly:

KAC SR-15 Carbine MOD 2 [14.5-in AR-15; KAC proprietary barrel extension, BCG, and gas system]
KAC SR-15 CQB MOD 2 [11.5-in AR-15; KAC proprietary barrel extension, BCG, and gas system]
Daniel Defense M4A1RIII [14.5-in AR-15; 0.076-in gas port at mid-length barrel location]
Daniel Defense MK18 [10.3-in AR-15; 0.070-in gas port at carbine-length barrel location]

The above combination of apparatus resulted in a 16-test evaluation matrix in the IR program, characterizing the blast and shock dynamics of each assembly. Free field overpressure histories were recorded during the full time regime of system operation and comprehensive waveform post-processing was performed. Personnel risk metrics were calculated using the PEW Science Suppression Rating, and external gas momentum transfer rates were calculated using the Omega Metric research parameter. Over 3 million individual data points were analyzed.

6.156.2 The PEW Science KAC 556 PRT System Optimization Tool

The above quantitative metrics, along with the physical system parameters of length and weight, were used to create the PEW Science KAC 556 PRT System Optimization Tool. This interactive tool is intended to aid end-users of the KAC 556 PRT silencer systems with optimization of system performance, in accordance with their use case. The tool may be used to investigate the following performance parameters and their interaction:

Personnel risk reduction (to both near-bystanders and the operator).
Close-quarters operational factors (gas momentum transfer rate and operator risk).
Handling factors (system length and perceived system weight).
Muzzle device choice performance influence.
Host weapon choice performance influence.

The below tool allows the user to view all metrics on the same scale, as all are normalized. Values of “0” represent metric minima in the 556 PRT dataset. Values of “1” represent maxima. The tool is available in both PEW Science Member and public versions of this report. Selected data publication from the IR program is presented in the following sections for incorporation into the public Silencer Sound Standard research pedigree. Suppression Rating metrics for all 16 IR program tests have been added to the PEW Science Rankings Section of the Standard.

Notes about flash signature: Flash signature suppression performance is a function of several physical phenomena which may vary in each of the 16 tested cases. Outside the scope of this program, ammunition choice also influences this performance. However, the following factors should be noted:

The tested KAC PRT silencers contain similar distal exit geometry.
The tested silencers also contain similar initial proximal expansion chamber features.
External gas momentum transfer rates are measured and reported.

With (1) and (2) held constant, the variation of (3) can somewhat approximate the likelihood for variation in flash signature. Laboratory personnel operation of both silencers in low light conditions anecdotally supports this conclusion. As noted in previous Surefire SOCOM556-RC3 system characterization (6.151), some high flow rate silencers may exhibit erratic external gas momentum propagation when varying muzzle device. This report addresses this potential erratic behavior in the selected data presentation.

6.156.3 High Level System Performance Summary

KAC Program Systems:
1. The QDC/CRS-PRT mounted to the KAC SR-15 Carbine MOD 2 with a 3-prong flash hider is the highest performing system, with regard to signature suppression performance, in this program. This complete system excels in both operator and bystander risk reduction.
2. The QDC/MCQ-PRT mounted to the KAC SR-15 Carbine MOD 2 with a 3-prong flash hider is shown to have somewhat less robust operator hazard reduction, compared to its mounting on the M4A1 mid-gas system; the highest MCQ performance case.
3. Both silencers achieve performance on the KAC SR-15 CQB MOD 2 host weapon that is somewhat similar to that achieved on the standard MK18. Bystander and operator risk tradeoffs should be examined with the provided tool.
4. The KAC SR-15 systems are shown to produce a higher degree of overall consistency in performance than the Daniel Defense systems, when suppressed with the silencers in this program. Gas system component and design factors are likely responsible.
5. The MAMS muzzle brake may sometimes increase suppression performance over that of the 3-prong flash hider, but not consistently. The MAMS is shown to sometimes increase gas momentum transfer rate from the distal end of the PRT systems. This may result in erratic behavior, somewhat similarly to mount variation in the recently evaluated Surefire RC3 system.
KAC PRT Silencer Systems and the Market At-Large:
6. The PRT systems perform comparably in signature suppression performance to the standard 556 QDC and other legacy KAC rifle silencer systems (QDSS-NT4), while operating with a higher flow rate throughout the entire time regime.
7. The mini size KAC CRS/MCQ-PRT produces operator hazard reduction on 14.5-barrel hosts that meets or exceeds that of the Surefire SOCOM556-MINI2, and is on-par with that of a full-size WARCOMP-equipped Surefire SOCOM556-RC2.
8. The full size KAC CRS/CRS-PRT exhibits higher performance than the MCQ system, with a length and weight penalty. The distal venting of both PRT silencers prevent them from reaching the free field muzzle suppression performance of some other silencers on 14.5-in barrels. The Surefire SOCOM556-RC2 with 3-Prong Mount and the CAT WB remain significant performance leaders in the M4A1 dataset, to date.
9. MK18 dataset performance comparison is robust. The mini sized KAC QDC/MCQ-PRT, equipped with the MAMS muzzle brake on the MK18, holistically outperforms both a Rugged Razor 7.62 and Energetic Armament ARX on this same weapon system, in hazard mitigation potential. The mini MCQ silencer falls short, but does almost approach, the performance of some larger 7.62 units in some metrics, such as the Surefire SOCOM762-RC2, Dead Air Sandman-S, and Thunder Beast Dominus on the MK18. This speaks to the importance of caliber/cartridge-specific silencer optimization for small arm weapon systems, in general. The full size KAC QDC/CRS-PRT performs on-par with the Surefire SOCOM556-RC3 on the MK18, but with a higher degree of consistency. It also outperforms silencers like the Dead Air Nomad-30.

The full-size 556 QDC/CRT-PRT and mini-size 556 QDC/MCQ-PRT are manufactured by KAC. They are 223 caliber centerfire rifle silencers, intended to suppress the 5.56x45mm NATO cartridge. The silencers have a 1.5-inch diameter and are 6.3 and 4.4 inches long, respectively. Both silencers mount to the host firearm with a proprietary Quick Disconnect (QDC) mounting system; the user may choose from various KAC QDC flash hider and muzzle brake mounts. The silencer bodies are constructed from DMLS (3D-printed) Inconel alloy. The silencer bodies with mount collars weigh 19.5 and 14.0 ounces, respectively. The 3-prong flash hider and MAMS brake mount weigh 2.5 and 2.3 ounces, respectively. The greatest tested system weights are therefore 22 and 16.5 ounces, respectively. The 556 QDC/CRS-PRT and 556 QDC/MCQ-PRT can be obtained from SK Arms.

This IR program contains 16 tests. From the full dataset, three tests have been selected for full raw data and analysis publication:

KAC QDC/CRS-PRT mounted to the KAC SR-15 Carbine MOD 2 14.5-in AR-15 with the 3-prong flash hider. This test is selected due to it demonstrating the highest possible overall suppression performance of the full-size 556 PRT silencer in the program.
KAC QDC/MCQ-PRT mounted to the M4A1RIII mid-gas 14.5-in AR-15 with the 3-prong flash hider. This test is selected due to it demonstrating the highest possible overall suppression performance of the mini-size 556 PRT silencer in the program.
KAC QDC/MCQ-PRT mounted to the MK18 10.3-in AR-15 with the MAMS muzzle brake. This test is selected due to it demonstrating the highest possible overall suppression performance, for the shortest overall system length, of the mini-size 556 PRT silencer in the program. This test is also selected for an excellent demonstration of erratic gas momentum propagation that may occur with mount variation in some high flow rate silencers.

Other tests from the program may be published at a later date. As it stands, the holistic performance characteristics of the KAC 556 PRT rifle silencers are well represented by the above. For comprehensive system comparison purposes, the above interactive tool is available, along with the PEW Science Rankings Table and Suppression Rating Visualization Tool (Members Only) in Section 7 of the Standard.

The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
The standard PEW Science M4A1 test host weapon system is described in Public Research Supplement 6.127.
Both KAC SR-15 Carbine MOD 2 and SR-15 CQB MOD 2 systems are non-standard hosts and not yet included elsewhere in the research pedigree.

All sets of test results in this Sound Signature Review were obtained with the respective weapon systems and silencers using Federal XM193 55gr ammunition.

Section 6.156.4 contains QDC/CRS-PRT evaluation on the 14.5-in SR-15 Carbine MOD 2 using the 3-Prong flash hider mount.
Section 6.156.5 contains QDC/MCQ-PRT evaluation on the 14.5-in M4A1 mid-gas using the 3-Prong flash hider mount.
Section 6.156.6 contains QDC/MCQ-PRT evaluation on the 10.3-in MK18 using the MAMS brake mount.
Section 6.156.7 contains overall Suppression Rating comparisons for both KAC silencers with both muzzle devices on all four host weapons (as used in the interactive tool).
Section 6.156.8 contains overall Suppression Rating comparisons on the 14.5-in M4A1 of all silencers in the dataset.
Section 6.156.9 contains overall Suppression Rating comparisons on the 10.3-in MK18 of all silencers in the dataset.
Section 6.156.10 contains an article summary and PEW Science laboratory staff opinions.

Summary: The KAC QDC/CRS-PRT mounted with the 3-Prong flash hider achieved a maximum composite Suppression Rating™ of 30.4 in PEW Science testing. The KAC QDC/MCQ-PRT mounted with the 3-Prong flash hider achieved a maximum composite Suppression Rating of 22.6 in PEW Science testing. With the QDC/MCQ-PRT in the shortest possible system configuration, the highest Suppression Rating of 21.8 was achieved with it mounted on the MAMS brake.
As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings of all 16 tested configurations. The provided optimization tool may assist the user with this, visually.
Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings

6.156.4 KAC QDC/CRS-PRT Sound Signature Test Results (Carbine MOD 2, 3-Prong)

A summary of the principal Silencer Sound Standard performance metrics of the KAC QDC/CRS-PRT with the 3-Prong Flash Hider 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. KAC QDC/CRS-PRT (3-Prong FH) Sound Metric Summary

6.156.4.1 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 QDC/CRS-PRT with the 3-Prong Flash Hider are shown in Figure 1a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 1b, in early time. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 2a. In Figure 2b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shots 2, 3, and 5.

Fig 1a. KAC QDC/CRS-PRT (3-Prong FH) 5.56x45mm NATO SR-15 Carbine MOD 2 Automatic Rifle Muzzle Sound Pressure Signature

Fig 1b. KAC QDC/CRS-PRT (3-Prong FH) 5.56x45mm NATO SR-15 Carbine MOD 2 Automatic Rifle Sound Pressure Signature

Figure 2a. KAC QDC/CRS-PRT (3-Prong FH) 5.56x45mm NATO SR-15 Carbine MOD 2 Automatic Rifle Muzzle Sound Impulse Signature

Figure 2b. KAC QDC/CRS-PRT (3-Prong FH) 5.56x45mm NATO SR-15 Carbine MOD 2 Automatic Rifle Muzzle Sound Impulse Signature

The KAC 556 QDC/CRS-PRT shares external design similarity with the previously evaluated, now legacy, KAC 556 QDC (6.104). However, the silencers are very different, both structurally and in internal geometry. The PRT series are high flow rate models, intended to maximize gas momentum transfer during the time regime before system extraction. The above test data displays performance factors that are indicative of that intent:

Relatively expedient blowdown and delayed late-time BCG return to battery (Fig. 1a).
Significant early-coupling of initial jetting, with significant pressure amplitude for the initial primary positive phase duration (Fig. 1b).
Relatively high initial rate of blast load impulse accumulation (Fig. 2a).

These performance factors are somewhat expected for a modern high flow rate rifle silencer on a standard AR-15 weapon system. However, what is somewhat unexpected is the consistency with which the QDC/CRS-PRT produces the holistic measured signatures.

PEW Science Research Note 1: The above consistency of the QDC/CRS-PRT is noteworthy, because it is not limited to testing on the KAC SR-15 Carbine MOD 2 shown, nor is it limited to this particular silencer. The mini-size QDC/MCQ-PRT also displays relative signature consistency, throughout the shot string, on multiple weapon systems (albeit with significantly higher amplitude signatures). It should further be noted that this conclusion is for 3-prong flash hider mounted systems. The MAMS muzzle brake may induce somewhat erratic signatures, particularly on the first shot, with the smaller model. This is not unlike the behavior of the Surefire SOCOM556-RC3 system (6.151), though the full size QDC/CRS-PRT is significantly less prone to this behavior.

PEW Science Research Note 2: In PEW Science laboratory testing, the modified Total Signature Reduction Technology in the Surefire SOCOM556-RC3 is shown to perform somewhat similarly to the Pressure Reduction Technology in the KAC QDC/CRS-PRT, but the KAC silencer provides significantly more consistent gas dynamics. PEW Science postulates that the flash suppression performance of the KAC silencer may exceed that of the Surefire silencer, as robust gas momentum propagation consistency is one factor that often correlates with flash suppression. More research is needed. QDC/CRS-PRT system FRP severity is shown to be somewhat reduced through the use of the MAMS brake, when compared to the use of the 3-Prong flash hider, but behavior may be somewhat more erratic with the MAMS brake. Overall performance comparisons should be made using the interactive tool in this report and the Rankings section of the Standard.

PEW Science Research Note 3: The PRT series silencers are DMLS manufactured (3D-printed) and the internal geometries are somewhat more complex than that of the legacy QDC systems. Early venting to alternating annular cavities with radial diffuser arrays in the first expansion chambers of the silencers reduce early-time blast impulse accumulation and allow late-time transfer to distal vent arrays. When combined with the distal vent geometry near the primary bore exit aperture, these features are intended to maintain a high flow rate while quenching secondary combustion; minimization of sharp temperature gradients along the shock boundaries may occur. The PRT systems perform comparably to the aforementioned QDC and other legacy KAC rifle silencer systems (like the QDSS-NT4) in suppression performance, while operating with a higher flow rate throughout the entire time regime. The flow paths within the QDC/CRS-PRT silencer are shorter than a Flow Through design, such as those by HUXWRX. And, this is reflected in the sound signature suppression performance when compared to that of silencers like the HUXWRX FLOW 762 Ti (6.114). Nonetheless, visual signature suppression performance differential comparison may favor the KAC unit, partially due to the titanium construction of the HUXWRX unit.

PEW Science Research Note 4: 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 5: 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 is unreliable upon upper receiver fouling. Sound signatures are not influenced by this fouling, as these kinematics occur in late time, after gas venting to atmosphere. Momentum transfer, weapon condition (upper receiver fouling), and other factors, can significantly influence bolt closing time. PEW Science urges the reader to exercise extreme caution if using the published bolt closing time to make determinations regarding silencer flow restriction (back pressure) or weapon system kinematics. This type of calculation may provide erroneous results, as the weapon condition at the time of each test is not published data. The time-scale duration showing bolt closing time is only published by PEW Science such that the signature data pedigree may be verified.

The shape, timing, and magnitudes of the early-time pressure pulses and overall shape of the impulse waveforms measured at the muzzle, from shot-to-shot, are relatively consistent. The consistency of the waveform amplitudes highlight the silencer’s overall sound performance consistency at the muzzle after the FRP, as well as the relative consistency of the tested automatic rifle firearm configuration.

As typically indicated, first-round sound signatures always differ from subsequent shots, as the atmosphere within the silencer changes. The FRP phenomenon cannot always be shown by viewing only the peak sound pressure. This is one of the reasons why The Silencer Sound Standard requires examining multiple sound signature metrics. Ammunition consistency can play a role in the determination of FRP, however, the close examination of measured pressure and impulse waveforms typically excludes ammunition from the possible factors influencing true FRP, due to the relative consistency of most high quality factory ammunition.

PEW Science Research Note 6: Note that the muzzle Suppression Rating of the QDC/CRS-PRT with the 3-Prong mount is 27.3 and the at-ear Suppression Rating is 26.6; the same zone on the Suppression Rating Dose Chart. The low back pressure of the QDC/CRS-PRT contributes to a less severe ejection port blast signature, and the result is relatively balanced performance on the SR-15 Carbine MOD 2 weapon system. Note that changing muzzle device, and weapon system, may change silencer performance (refer to interactive tool at the beginning of this report).

The signatures measured at the shooter’s ear are presented below.

6.156.4.2 SOUND SIGNATURES AT SHOOTER’S EAR

Real sound pressure histories from the same 6-shot test acquired with PEW-SOFT at the shooter’s ear are shown below. Again, the waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz).

The primary sound signature pressure histories at the ear for all 6 shots are shown in Figure 3. The primary sound signature history is shown in Figure 3a. An annotated timescale is displayed in Figure 3b, 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 4. Again, full and short timescales are shown.

Figure 3a. KAC QDC/CRS-PRT (3-Prong FH) 5.56x45mm NATO SR-15 Carbine MOD 2 Automatic Rifle Ear Sound Pressure Signature

Figure 3b. KAC QDC/CRS-PRT (3-Prong FH) 5.56x45mm NATO SR-15 Carbine MOD 2 Automatic Rifle Ear Sound Pressure Signature, Short Time Window

Figure 4a. KAC QDC/CRS-PRT (3-Prong FH) 5.56x45mm NATO SR-15 Carbine MOD 2 Automatic Rifle Ear Sound Impulse Signature

Figure 4b. KAC QDC/CRS-PRT (3-Prong FH) 5.56x45mm NATO SR-15 Carbine MOD 2 Automatic Rifle Ear Sound Impulse Signature Peaks

The high flow rate of the PRT series pays dividends in ejection port blast signature severity at the operator’s head. Additionally, the KAC SR-15 system exhibits lower gas impulse generation than the Daniel Defense M4A1RIII system. Both silencer and host factors influence operator risk. The interactive tool highlights the difference between operator risks between the two weapon systems.

In the above measured data from the SR-15, hallmark features of low backpressure behavior are present, to include front-loaded FRP in blast impulse space (Fig. 4b) and expedient blowdown in pressure space (Fig. 3a).

The signatures measured at the operator’s head from the CRS silencer have direct relation to those measured in the free field, presented in the previous section. Despite the low system backpressure, the operator is still subjected to ejection port blast load at a close proximity, which is nested with the blast loads from muzzle signature propagation.

PEW Science Research Note 7 (repeated from previous publications): There are additional features in the CRS signatures measured at the operator’s head that mirror those of systems in which ejection port blast has been minimized or reduced. Recall the “tuned” MK18 system analysis presented of the Maxim Defense DSX / SURG system in test report 6.111. In that report, a high back pressure silencer (the Maxim Defense DSX) was examined on a tuned upper receiver group. When comparing the DSX operator hazard on the standard MK18 (6.110) to the DSX operator hazard on a tuned system (6.111), significantly front-loaded blast impulse accumulation was noted (Fig. 4b, 6.111.1.2). This type of impulse accumulation timing is the result of muzzle blast wave energy “outrunning” that of ejection port pulse. Because the ejection port blast is so reduced in a tuned system (or in a low back pressure system), the balance of impulse accumulation during FRP, with respect to follow-up shots, is biased to early time.

The aforementioned phenomenon is almost always present in low back pressure silencer applications. The shift of relative FRP impulse timing is also influenced by FRP severity. As a result, so-called balanced designs may display both front-loaded and back-loaded FRP impulse phenomena. These types of designs may excel at FRP suppression, have high early-time flow rate, and may control momentum propagation in the free field, resulting in overall “high performance.” An example of such silencers is the SOCOM556-RC2 (see Fig. 4b, 6.52.1.2). A modern, more extreme example of balanced high performance is the CAT WB (see Fig. 4b, 6.129.1.2).

The QDC/CRS-PRT, as well as the previous generation QDC and NT4 present a relatively “balanced” shooter’s ear signature on this weapon system, when considering the contributions from both muzzle blast and ejection port blast to the hazard, with the PRT system greatly improving this balance.

Testing and analysis results for the mini silencer in the PRT series follow.

6.156.5 KAC QDC/MCQ-PRT Sound Signature Test Results (M4A1RIII, 3-Prong)

A summary of the principal Silencer Sound Standard performance metrics of the KAC QDC/MCQ-PRT with the 3-Prong Flash Hider is shown in Table 2. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. As previously stated, 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 2. KAC QDC/MCQ-PRT (3-Prong FH) Sound Metric Summary

6.156.5.1 SOUND SIGNATURES AT THE MUZZLE

Real sound pressure histories from a 6-shot test acquired with PEW-SOFT™ are shown below. The waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz). The peaks, shape, and time phasing (when the peaks occur in relation to absolute time and to each other) of these raw waveforms are the most accurate of any firearm silencer testing publicly available. PEW-SOFT data is acquired by PEW Science independent testing; the industry leader in silencer sound research. For more information, please consult the Silencer Sound Standard.

The primary sound signature pressure histories for all 6 shots with the QDC/MCQ-PRT with the 3-Prong Flash Hider are shown in Figure 5a. The sound signatures of Shot 1 and Shot 2 are shown in a smaller time window in Figure 5b. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 6a. In Figure 6b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shot 2, Shot 3, and Shot 4.

Fig 5a. KAC QDC/MCQ-PRT (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Pressure Signature

Fig 5b. KAC QDC/MCQ-PRT (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Pressure Signature, Short Time Window

Fig 6a. KAC QDC/MCQ-PRT (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature

Fig 6b. KAC QDC/MCQ-PRT (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Muzzle Sound Impulse Signature, Short Time Window

In contrast with the full size QDC/CRS-PRT, the mini size KAC QDC/MCQ-PRT exhibits extremely high external gas momentum transfer rate. This should be expected, based on the silencer’s size and internal design. Significant blast propagation features of note in the above raw test data are:

Very high amplitude blast overpressure in the free field with highly expedient blowdown (Fig. 5a).
Significantly pronounced positive phase shock duration and pronounced negative phase (Fig. 5b).
Extremely rapid rise to maximum peak positive phase blast load impulse (Fig. 6a).

Interestingly, despite the relatively severe raw blast loads measured in the program, both the consistency and the personnel risk reduction potential from the MCQ system is relatively notable.

PEW Science Research Note 8: FRP From the MCQ system is minimal. This is partially due to its size and flow rate, which dictate FRP differential to be minimized, in general. Nonetheless, there are measurable factors present in the above data displaying FRP and the most significant is the pure coupling of the initial shock front during the first shot (Fig. 5b). This initial full coupling of the multiple vented jet loads, transitioning to a clear stepped coalescence in subsequent shots, indicates that the silencer is, in fact, capable of generating enough volumetric gas expansion delay to compete with suppression performance of larger silencers. Despite its size, its behavior is still silencer-like. This may be counterintuitive to some readers, as the size of such systems are often indications of significantly poor suppression performance. On the contrary, the MCQ produces operator hazard reduction on this host that exceeds that of the Surefire SOCOM556-MINI2 (6.144), and is on-par with that of a full-size WARCOMP-equipped Surefire SOCOM556-RC2 (6.128). This is extremely notable. The comparison of the MCQ performance with other silencers is discussed in Section 6.156.8 and Section 6.156.9 of this report.

Furthermore, the performance comparison of mini silencers like the KAC QDC/MCQ-PRT with unsuppressed configurations has drastic contrast. The signature from a system suppressed with the MCQ silencer is significantly less severe than that from an unsuppressed rifle. The raw blast load measurements, alone, should reinforce this conclusion to the reader. Please reference typical raw unsuppressed blast load measurements here.

The signatures measured at the shooter’s ear are presented below.

6.156.5.2 SOUND SIGNATURES AT SHOOTER’S EAR

The primary sound signature pressure histories at the ear for all 6 shots with the QDC/MCQ-PRT with the 3-Prong Flash Hider are shown in Figure 7a. A zoomed-in timescale is displayed in Figure 7b, in the region of peak sound pressure. The real sound impulse (momentum transfer potential) histories at the ear from the same 6-shot test are shown in Figure 8.

Fig 7a. KAC QDC/MCQ-PRT (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature

Fig 7b. KAC QDC/MCQ-PRT (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Pressure Signature, Short Time Window

Fig 8a. KAC QDC/MCQ-PRT (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature

Fig 8b. KAC QDC/MCQ-PRT (3-Prong FH) 5.56x45mm NATO M4A1 Automatic Rifle Ear Sound Impulse Signature, Short Time Window

Despite it’s small size, the MCQ silencer does afford the operator significant blast overpressure protection when compared to unsuppressed fire, and meets or exceeds the performance of several larger systems in doing so.

Features like significantly decoupled ground reflection (Fig. 7) and front-loaded FRP (Fig. 8) directly illustrate the performance space between significant blast hazards of unsuppressed systems and simple personnel safety decisions such as minimally-intrusive blast mitigating devices. Protective equipment, even if minimal, can greatly reduce personnel hazards from small arms. The QDC/MCQ-PRT is an excellent example of that in the research pedigree.

The above performance is from a 14.5-in barrel. Short 10.3-in barrel performance, using the MAMS brake to illustrate additional performance factors, follows.

6.156.6 KAC QDC/MCQ-PRT Sound Signature Test Results (MK18, MAMS)

A summary of the principal Silencer Sound Standard performance metrics of the KAC QDC/MCQ-PRT with the MAMS Brake is shown in Table 2. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. As previously stated, 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 3. KAC QDC/MCQ-PRT (MAMS Brake) Sound Metric Summary

6.156.6.1 SOUND SIGNATURES AT THE MUZZLE

The primary sound signature pressure histories for all 6 shots with the QDC/MCQ-PRT with the MAMS Brake are shown in Figure 9a. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 9b.

Fig 9a. KAC QDC/MCQ-PRT (MAMS Brake) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature

Fig 9b. KAC QDC/MCQ-PRT (MAMS Brake) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature

On the shortest 5.56x45mm test host barrel in the Standard, the KAC QDC/MCQ-PRT does demonstrate significant blast load propagation. However, again, the performance comparison of mini silencers like the KAC QDC/MCQ-PRT with unsuppressed configurations has drastic contrast. The signature from a system suppressed with the MCQ silencer is significantly less severe than that from an unsuppressed rifle. The raw blast load measurements, alone, should reinforce this conclusion to the reader. Please reference typical raw unsuppressed blast load measurements here.

PEW Science Research Note 9: The choice to select the QDC/MCQ-PRT MAMS-mounted MK18 data for publication in this report is primarily highlighted in Figure 9b. In the figure, which displays gross blast load impulse, significant FRP momentum is apparent. This behavior was not common in the research program. PEW Science postulates its occurrence to be the result of three primary factors:

The short 10.3-in barrel.
The size of the MCQ assembly, for the type of design.
The MAMS muzzle brake, and its influence on initial jet propagation into the first expansion chamber.

It is the combination of (1), (2), and (3) that form the risk basis for FRP blast load impulse propagation shown in the above figure. No other testing of the MCQ system displayed this behavior. That is not to say it is impossible to achieve this propagation outside this tested configuration. On the contrary, there exist several indications that MAMS muzzle brake use may produce erratic gas propagation in PRT systems. The interactive tool at the beginning of this report can be used to illustrate this phenomenology. There is an increase in gas momentum transfer rate on the MK18 when using the MAMS, albeit slight. Such an increase, at these already high rates, may sometimes overwhelm the capability of the silencer during first-shot use. Again, it is not necessarily a guaranteed occurrence. This is the nature of erratic dynamics when combining the above factors.

As previously highlighted, the MCQ system does exhibit notable consistency, even on short barrel hosts (erratic FRP in the MAMS configuration notwithstanding).

6.156.6.2 SOUND SIGNATURES AT SHOOTER’S EAR

The primary sound signature pressure histories at the ear for all 6 shots with the QDC/MCQ-PRT with the MAMS Brake are shown in Figure 10a. The real sound impulse (momentum transfer potential) histories at the ear from the same 6-shot test are shown in Figure 10b.

Fig 10a. KAC QDC/MCQ-PRT (MAMS) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature

Fig 10b. KAC QDC/MCQ-PRT (MAMS) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature

Predictably, the signatures measured at the operator’s location exhibit features that indicate propagation of blast load phenomena from the distal end of the silencer (the weapon muzzle). And, ejection-port blast propagation is significantly minimized, as expected.

Somewhat unpredictably, the very large FRP divergence measured at the operator’s location adversely influences the risk to the operator less than expected, when compared to subsequent shots, in accordance with PEW Science analysis. It is possible that, at these amplitudes and rise times, that the impulse sensitivity of inner ear response drops in certain time regimes. Pressure-driven risk may be exacerbated and early pressure propagation may cause greater, immediate damage. More research into this phenomenon is needed.

This concludes the selected raw data presentation portion of this report. Gross Suppression Rating comparisons of silencers in this program, and in the public research pedigree, are provided below. Hang in there, you’re in the home stretch. (that note is for you, as much as it is for us).

6.156.7 Suppression Rating Comparison (5.56x45mm from all Hosts in Program)

Figure 11 presents a comparison of the PEW Science Suppression Ratings of the KAC QDC/CRS-PRT and QDC/MCQ-PRT with both the 3-Prong Flash Hider and MAMS brake mounts on all four host weapons in this test program. This is the same Suppression Rating data included in the interactive tool, plotted on a bar chart. As the legend states, the Ratings are “absolute,” and not normalized like they are in the tool.

Figure 11. Suppression Rating Comparisons of the KAC QDC/CRS-PRT and QDC/MCQ-PRT with different mounts on Four Different Hosts, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis

Trends may be examined using the interactive tool, the above bar chart, or the Rankings Table in Section 7 of the Standard.

Standard M4A1RIII performance of the KAC silencers is compared with that of other tested models in the following section.

6.156.8 Suppression Rating Comparison (5.56x45mm from the M4A1RIII)

Figure 12 presents a comparison of the PEW Science Suppression Ratings of the KAC QDC/CRS-PRT and QDC/MCQ-PRT with both the 3-Prong Flash Hider and MAMS brake mounts with that 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. As PEW Science research with the M4A1 system continues, the dataset will be further populated.

Figure 12. Suppression Rating Comparisons of the KAC QDC/CRS-PRT and QDC/MCQ-PRT with the Surefire SOCOM556-MINI2, SOCOM556-RC2, and CAT WB on the M4A1RII, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis

The mini size KAC CRS/MCQ-PRT produces operator hazard reduction on this host that meets or exceeds that of the Surefire SOCOM556-MINI2 (6.144), and is on-par with that of a full-size WARCOMP-equipped Surefire SOCOM556-RC2 (6.128). This is extremely notable.

The full size KAC CRS/CRS-PRT exhibits higher performance than the MCQ system, with a length and weight penalty. The distal venting of both PRT silencers prevent them from reaching the free field muzzle suppression performance of the other silencers. The Surefire SOCOM556-RC2 with 3-Prong Mount and the CAT WB (6.130) remain significant performance leaders in the M4A1 dataset, to date.

6.156.9 Suppression Rating Comparison (5.56x45mm from the MK18)

Figure 13 presents a comparison of the PEW Science Suppression Ratings of the KAC QDC/CRS-PRT and QDC/MCQ-PRT with both the 3-Prong Flash Hider and MAMS brake mounts with that of several other silencers on the MK18 weapon system. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.

Figure 13. Suppression Rating Comparisons of the KAC QDC/CRS-PRT and QDC/MCQ-PRT with different mounts and other silencers on the MK18, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis

Figure 13 presents an overall summary of the postulated hazards to the operator and bystanders when fielding a variety of different silencers on the standard MK18 weapon system. This is the largest 5.56x45mm dataset in the pedigree, and allows for a significant amount of contextual comparative analysis.

Notable conclusions include:

The mini sized KAC QDC/MCQ-PRT, equipped with the MAMS muzzle brake on the MK18, holistically outperforms both a Rugged Razor 7.62 (6.58) and Energetic Armament ARX (6.82) on this same weapon system, in hazard mitigation potential.
The mini MCQ silencer falls short, but does almost approach, the performance of some larger 7.62 units in some metrics, such as the Surefire SOCOM762-RC2 (6.73), Dead Air Sandman-S (6.92), and Thunder Beast Dominus (6.105) on this weapon system. This speaks to the importance of caliber/cartridge-specific silencer optimization for small arm weapon systems, in general.
The full size KAC QDC/CRS-PRT performs on-par with legacy KAC QDSS-NT4 (6.78) and KAC 556 QDC (6.104) silencers on the MK18, and does so with a significantly higher flow rate.
The KAC QDC/CRS-PRT performs on-par with the Surefire SOCOM556-RC3 (6.151) on the MK18, but with a higher degree of consistency. It also outperforms silencers like the Dead Air Nomad-30 (6.100).

In PEW Science laboratory testing, the modified Total Signature Reduction Technology in the Surefire SOCOM556-RC3 is shown to perform somewhat similarly to the Pressure Reduction Technology in the KAC QDC/CRS-PRT, but the KAC silencer provides significantly more consistent gas dynamics. PEW Science postulates that the flash suppression performance of the KAC silencer may exceed that of the Surefire silencer, as robust gas momentum propagation consistency is one factor that often correlates with flash suppression. More research is needed. QDC/CRS-PRT system FRP severity is shown to be somewhat reduced through the use of the MAMS brake, when compared to the use of the 3-Prong flash hider, but behavior may be somewhat more erratic with the MAMS brake. Overall performance comparisons should be made using the interactive tool in this report and the Rankings section of the Standard.

As detailed in this report, the Suppression Rating at the shooter’s ear may be significantly influenced by the ejection port signature from an AR15; all other things equal. For details on performance increases that are possible when “tuning” an AR-15 weapon system for a silencer, please see Review 6.111. It is important to note that not all silencers will possess a significant increase in shooter’s ear Suppression Rating from weapon tuning. 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. The evaluations of the KAC PRT systems detailed in this report provide yet another example of modifying a legacy technology to achieve more advanced flow dynamics. Balancing performance across the external pressure field, while controlling a high distal flow rate, is an advanced suppressed small arm weapon system engineering task. This challenge continues to significantly influence weapon operator hazard reduction 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.

6.156.10 Review Summary: KAC 556 QDC/CRS-PRT and 556 QDC/MCQ PRT System Optimization with Two Muzzle Devices on Four Hosts

The KAC QDC/CRS-PRT mounted with the 3-Prong flash hider achieved a maximum composite Suppression Rating™ of 30.4 in PEW Science testing. The KAC QDC/MCQ-PRT mounted with the 3-Prong flash hider achieved a maximum composite Suppression Rating of 22.6 in PEW Science testing. With the QDC/MCQ-PRT in the shortest possible system configuration, the highest Suppression Rating of 21.8 was achieved with it mounted on the MAMS brake.

As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings of all 16 tested configurations. The provided optimization tool may assist the user with this, visually.

Report Summary and PEW Science Laboratory Staff Opinion:

The KAC 556 PRT silencers are an evolution of the legacy Inconel QDSS-NT4 design. The 556 QDC/CRS-PRT and QDC/MCQ-PRT represent the latest iteration of 5.56mm rifle silencers from KAC exhibiting high flow rate throughout the entire time regime. The silencers are DMLS manufactured and mount to host weapon systems using the KAC Quick Detach system; a simple and secure technology. The PRT series maintains much of the signature suppression performance of legacy KAC QDC and NT4 designs, while offering reduced operator hazard potential. This comprehensive research program examines the performance of both 556 PRT silencers mounted with multiple muzzle devices across multiple weapon systems.
The PRT series silencers are DMLS manufactured (3D-printed) and the internal geometries are somewhat more complex than that of the legacy QDC systems. Early venting to alternating annular cavities with radial diffuser arrays in the first expansion chambers of the silencers reduce early-time blast impulse accumulation and allow late-time transfer to distal vent arrays. When combined with the distal vent geometry near the primary bore exit aperture, these features are intended to maintain a high flow rate while quenching secondary combustion; minimization of sharp temperature gradients along the shock boundaries may occur. The PRT systems perform comparably to the aforementioned QDC and other legacy KAC rifle silencer systems (like the QDSS-NT4) in suppression performance, while operating with a higher flow rate throughout the entire time regime. The flow paths within the QDC/CRS-PRT silencer are shorter than a Flow Through design, such as those by HUXWRX. And, this is reflected in the sound signature suppression performance when compared to that of silencers like the HUXWRX FLOW 762 Ti. Nonetheless, visual signature suppression performance differential comparison may favor the KAC unit, partially due to the titanium construction of the HUXWRX unit.
Two mounts were used in testing of the PRT silencer systems; the 3-Prong flash hider and the MAMS muzzle brake. The silencers attach to the mounts using a simple, yet robust mechanism that forces ball bearings into machined detents on the mount exterior. The silencer mount collar is turned to secure the bearings in place, locking the silencer onto the mount. This mechanism, including the included index pin to ensure identical clocking of the system upon each installation, remains attractive to many users for both convenience and security.
These iterations of KAC silencers are DMLS 3D-printed Inconel alloy. The durability of these systems may be extreme. The user should note that with all 3-prong muzzle device systems, there is a risk of jet-cut erosion of baffle material during operation on short-barrel 5.56x45mm weapon systems. While it is likely that the use of the MAMS muzzle brake may prevent or prolong the incidence of this phenomenon, the user must balance other performance factors and unsuppressed use preference with muzzle device choice.
The evaluations of the KAC PRT systems detailed in this report provide yet another example of modifying a legacy technology to achieve more advanced flow dynamics. Balancing performance across the external pressure field, while controlling a high distal flow rate, is an advanced suppressed small arm weapon system engineering task. This challenge continues to significantly influence weapon operator hazard reduction efficacy.
KAC Program System Performance Summary:
1. The QDC/CRS-PRT mounted to the KAC SR-15 Carbine MOD 2 with a 3-prong flash hider is the highest performing system, with regard to signature suppression performance, in this program. This complete system excels in both operator and bystander risk reduction.
2. The QDC/MCQ-PRT mounted to the KAC SR-15 Carbine MOD 2 with a 3-prong flash hider is shown to have somewhat less robust operator hazard reduction, compared to its mounting on the M4A1 mid-gas system; the highest MCQ performance case.
3. Both silencers achieve performance on the KAC SR-15 CQB MOD 2 host weapon that is somewhat similar to that achieved on the standard MK18. Bystander and operator risk tradeoffs should be examined with the provided tool.
4. The KAC SR-15 systems are shown to produce a higher degree of overall consistency in performance than the Daniel Defense systems, when suppressed with the silencers in this program. Gas system component and design factors are likely responsible.
5. The MAMS muzzle brake may sometimes increase suppression performance over that of the 3-prong flash hider, but not consistently. The MAMS is shown to sometimes increase gas momentum transfer rate from the distal end of the PRT systems. This may result in erratic behavior, somewhat similarly to mount variation in the recently evaluated Surefire RC3 system.
KAC PRT Systems and the Market At-Large Comparative Performance Summary:
6. The PRT systems perform comparably in signature suppression performance to the standard 556 QDC and other legacy KAC rifle silencer systems (QDSS-NT4), while operating with a higher flow rate throughout the entire time regime.
7. The mini size KAC CRS/MCQ-PRT produces operator hazard reduction on 14.5-barrel hosts that meets or exceeds that of the Surefire SOCOM556-MINI2, and is on-par with that of a full-size WARCOMP-equipped Surefire SOCOM556-RC2.
8. The full size KAC CRS/CRS-PRT exhibits higher performance than the MCQ system, with a length and weight penalty. The distal venting of both PRT silencers prevent them from reaching the free field muzzle suppression performance of some other silencers on 14.5-in barrels. The Surefire SOCOM556-RC2 with 3-Prong Mount and the CAT WB remain significant performance leaders in the M4A1 dataset, to date.
9. MK18 dataset performance comparison is robust. The mini sized KAC QDC/MCQ-PRT, equipped with the MAMS muzzle brake on the MK18, holistically outperforms both a Rugged Razor 7.62 and Energetic Armament ARX on this same weapon system, in hazard mitigation potential. The mini MCQ silencer falls short, but does almost approach, the performance of some larger 7.62 units in some metrics, such as the Surefire SOCOM762-RC2, Dead Air Sandman-S, and Thunder Beast Dominus on the MK18. This speaks to the importance of caliber/cartridge-specific silencer optimization for small arm weapon systems, in general. The full size KAC QDC/CRS-PRT performs on-par with the Surefire SOCOM556-RC3 on the MK18, but with a higher degree of consistency. It also outperforms silencers like the Dead Air Nomad-30.
In this review, the KAC QDC/CRS-PRT and QDC/MCQ-PRT performance metrics depend upon suppressing a supersonic centerfire rifle cartridge on multiple short barrel gas-operated rifles, 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.

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SSS.6.156 - KAC 556 QDC/CRS-PRT and 556 QDC/MCQ-PRT System Optimization: SR-15 Carbine MOD 2, CQB MOD 2, M4A1RIII, and MK18 5.56x45mm Short Barrel Automatic AR15 Rifles

KAC 556 QDC/CRS-PRT and 556 QDC/MCQ-PRT System Optimization with Two Muzzle Devices on Four Hosts

6.156.1 Program Scope and Test Specimens

6.156.2 The PEW Science KAC 556 PRT System Optimization Tool

6.156.3 High Level System Performance Summary