SSS.6.222 - JK Armament PRO-KOR 556K and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle
/JK Armament PRO-KOR 556K on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The PRO-KOR 556K is designed and manufactured by JK Armament. It is a .223 caliber centerfire rifle silencer, optimized to suppress the 5.56x45mm NATO cartridge and is also compatible with .243 cartridges such as 6mm ARC. It has a 1.72-in diameter and is 5.4 inches long with no mount installed. The rear of the silencer is threaded 1.375-24tpi to accommodate “HUB” compatible mounting systems; the included War Eagle mount and coupler increases the total system length to 6.22 inches. The first expansion chamber, end cap, and muzzle device are stainless steel, whereas the baffle core is 3D-printed Haynes 282 (nickel-chromium-cobalt alloy). The HUB mount coupler is titanium. The core of the silencer weighs 14.5 ounces and the 1/2-28tpi War Eagle mount and coupler weigh 4.4 ounces, for a total system weight of 18.9 ounces, as tested. The PRO-KOR 556K can be obtained from Silencer Shop.
Silencer Hazard Map:
The predicted personnel hazards generated by the tested weapon system 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 8.1.19 for further details. The PEW-SOFT HD Blast Hazard Prediction Tool and Hazard Mapper is presented in Report 8.1.1.
JK Armament PRO-KOR 556K 10.3-in MK18 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-JK-140-001-25. Therefore, data pertaining to the PRO-KOR 556K in this Sound Signature Review is published with the express written permission of JK Armament.
The testing and analysis presented in this Sound Signature Review is of the JK Armament PRO-KOR 556K mounted with the included War Eagle mount on the MK18 Automatic AR15 rifle rifle, chambered in 5.56x45mm NATO with a 10.3-inch barrel. Federal XM193 55gr ammunition was used in the test. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Report Table of Contents:
Section 6.222.1 contains a JK Armament PRO-KOR 556K performance summary comparison with other silencers that form the extreme ends of the Personnel Risk spectrum on a suppressed 5.56 AR-15 SBR
Section 6.222.2 contains JK Armament PRO-KOR 556K test results and analysis on the standard untuned MK18.
Section 6.222.3 contains overall Suppression Rating comparisons of the JK Armament PRO-KOR 556K with dedicated 223 and 30 caliber silencers on the current market, including the Stealth Additive Works Tisha, CAT CACM 556, CAT KK, FOR Systems Monarch Recce, Engaged Industries Operator 5.56, Q Southpaw, Centurion Arms Maximus-L, Otter Creek Labs Infinity, PTR VENT Spiritus 556i, LMT AT ION LT, HUXWRX FLOW 556 Ti, Off Grid Operator Ti, Surefire SOCOM556-MINI2, KAC QDC/CRS-PRT, KAC QDC/MCQ-PRT, Surefire SOCOM556-RC3, Otter Creek Labs Polonium-30, AAC M4-2000 Mod 08, PTR VENT 3, SilencerCo Velos LBP, BOSS Guillotine, CAT WB, PWS BDE 556, CAT ODB, Aero Precision Lahar-30L, Lahar-30, HUXWRX FLOW 762 Ti, Maxim Defense DSX, Thunder Beast Dominus, KAC 5.56 QDC, CGS SCI-SIX, Dead Air Nomad-30, YHM Turbo T2, Dead Air Sandman-S, HUXWRX FLOW 556k, Energetic Armament ARX, KAC QDSS-NT4, Rugged Razor556, Otter Creek Labs Polonium and Polonium-K, Surefire SOCOM556-RC2, HUXWRX HX-QD 556 and HX-QD 556k, Q Trash Panda, CGS Helios QD, SilencerCo Saker 556, Rugged Razor762, and others.
Section 6.222.4 contains an article summary and PEW Science laboratory staff opinions.
Summary: When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the JK Armament PRO-KOR 556K with the War Eagle mount achieved a composite Suppression Rating™ of 40.4 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
6.222.1 JK Armament PRO-KOR 556K Performance Summary and Extreme Ends of Personnel Risk on a Suppressed 5.56 AR-15 SBR
Not all centerfire rifle silencers produce the same suppression performance. Not all silencer technology is created equal.
The suppression performance of a silencer on a given small arm weapon system dictates the following two parameters:
Personnel protection of the operator and bystanders from blast overpressure hazard, both in the free field and near surfaces and confined spaces. Blast overpressure at amplitudes generated by small arms can harm a human’s inner ears and brain.
Signature detection by adversaries. Muzzle blast is the primary audible source that may be suppressed to mask position.
The past 6 years of public research by PEW Science in the Silencer Sound Standard has produced a dataset suitable for examination of technology performance trends, particularly in the case of short barrel reciprocating weapon systems firing the 5.56x45mm NATO intermediate rifle cartridge.
This report presents a third-party laboratory performance evaluation of the JK Armament PRO-KOR 556K silencer on the standard untuned 10.3-in MK18. The PRO-KOR 556K produces performance that places it in the Top 5 MK18 Rankings as of the date of this report publication. It is therefore useful to summarize both the Top 5 performers and Bottom 5 performers, so that the aforementioned performance realities can be easily understood by the reader, contextually. The reader may sort and filter all public Rankings here.
Objectively, the top five performers are the safest for personnel and are likely to mask operator position from adversaries to the greatest degree. Also objectively, the bottom five performers produce the most dangerous environment for personnel and are likely to provide the least concealment of audible signature.
The top five performing systems on the MK18 showcased in public evaluations are:
JK Armament PRO-KOR 556K (6.222); this report
The bottom five performing systems on the MK18 showcased in public evaluations are:
The performance disparity between the top 5 silencers and bottom five silencers is the result of technological advancement. All 5 top performers are hybrid designs. Two (the Surefire silencers), and arguably one (the KAC silencer) have hybrid design elements that pre-date the rest of the group. Surefire hybrid technology was derived from early OPS Inc. technology (see here).
The modern hybrid designs provide the greatest performance potentials while balancing operator and bystander protection and weapon system reliability and longevity. Specifically, these types of silencers use early venting and different pressure stages to relieve stagnation and increase suppression efficiency in a given design envelope, while also significantly reducing back pressure. Hybrid designs are not Flow Through silencers, and misclassification is commonplace in the silencer industry; no Flow Through silencers exist other than those manufactured by HUXWRX (formerly OSS). For more details, performance evaluations, and in-depth signature comparisons of hybrid and conventional designs, the reader may examine analysis that is previously published in:
Member Research Supplement 6.103 (supersonic 5.56 NATO)
Member Research Supplement 6.115 (supersonic 7.62 NATO)
Member Research Supplement 6.124 (subsonic 300 BLK)
Member Research Supplement 6.169 (supersonic 5.56 NATO), and recently
Member Research Supplement 6.184 (subsonic 9mm).
To be clear, it is not the addition of a single design element that produces high performance from a small arm weapon system silencer. It is the combination and purposefully engineered integration of multiple design elements that give way to high holistic system performance.
The raw performance of the JK Armament PRO-KOR 556K is illustrated in Figure 1, below, along with that of the aforementioned top 5 and bottom 5 performing silencers on the MK18. The 3D-printed internal structure of the PRO-KOR 556K not only possesses expedient blast chamber venting, but spiral geometry flow shaping features on each baffle, dual cavity baffle walls forming continuous pressure staging, and distal circumferential venting at its end cap. Its flow rate is relatively high and its blast momentum propagation is relatively controlled (significantly controlled when compared to the silencers in the MK18 dataset at large).
The host weapon system in Figure 1 is kept constant, and metrics shown are in terms of PEW Science Suppression Rating, which is a human risk metric calculated from raw free field blast overpressure test data. The calculated risk metrics for the unsuppressed case are also presented.
Figure 1. Suppression Rating Comparisons of the Top 5 Safest and Most Dangerous rifle silencers Using PEW-SOFT 5.56x45mm Supersonic MK18 Test Data and PEW Science Analysis
From the above data, two primary conclusions are apparent:
Silencer over-bore, in general, may reduce suppression performance. Both Surefire silencers and the Rugged silencer are 7.62 weapon system silencers that found historical popular and industry-recommended use on 5.56 weapon systems. The Energetic Armament silencer was purposely over-bored in an effort to reduce baffle erosion under heavy firing schedules. The KAC silencer is not significantly over-bored, but is relatively primitive in its design and its technology is not appropriate to produce high performance in the given system length envelope. Note that there are exceptions to over-bore performance reductions. That discussion is outside the scope of this report.
Rifle silencer suppression technology continues to advance at a rapid pace. The Stealth Additive Works, CAT SURGE BYPASS, PTR PIP, and HUXWRX Flow Through technologies are all extremely advanced. The JK Armament design implemented in the PRO-KOR 556K joins these technologies to form the current state of the art in short barrel rifle suppression. In general, these systems are also optimized and produced with advanced manufacturing.
Additive manufacturing is required in order to implement the engineering solutions present in many of the most advanced silencers. However, it is not only purposeful design and advanced manufacturing that can contribute to high performance for the end user. Some designs perform better than others, even in the same size classes; there are clear behavioral differences that are showcased with real measured test data and engineering analysis. The performance differentials may be nontrivial, even between new technologies released today. The above metrics are calculated from test data generated on a standard untuned host; weapon system tuning may raise performance potentials, as has been demonstrated in previous public research.
Detailed JK Armament PRO-KOR 556K test data and analysis follows.
6.222.2 JK Armament PRO-KOR 556K Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the JK Armament PRO-KOR 556K 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. JK Armament PRO-KOR 556K Sound Metric Summary
6.222.2.1 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 JK Armament PRO-KOR 556K are shown in Figure 2a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 12b, 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. JK Armament PRO-KOR 556K 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 2b. JK Armament PRO-KOR 556K 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature
Figure 3a. JK Armament PRO-KOR 556K 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 3b. JK Armament PRO-KOR 556K 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
The JK Armament PRO-KOR 556K is a relatively advanced hybrid design. Features of note in the silencer include early blast chamber venting, spiral geometry flow shaping features on each baffle with dual cavity baffle walls for pressure staging, and distal circumferential venting. Its removable end cap also possesses venting, though it has considerably less vent area.
The 3D-printed internal design features of the PRO-KOR 556K allow it to control blast momentum propagation to a significant degree when compared to many silencers previously evaluated on the MK18 weapon system. The risk field is forward-biased, away from the operator and adjacent bystanders, as illustrated in the Hazard Map at the beginning of this report and in Silencer Hazard Map Brief 8.1.19.
PEW Science Research Note 1: The following observations are made from the above test data:
Relatively low free field blast overpressure amplitude through the entire time regime with relatively late time bolt carrier group (BCG) return to battery (Fig. 2a).
Significant but controlled primary jetting followed by a relatively long duration blast momentum throttle (Fig. 2b and Fig. 3).
Consistency after first-round-pop (FRP) is high to moderate throughout blowdown with FRP momentum throttled soon after peak accumulation (Fig. 3b).
It is likely that the primary jetting behavior observed in (2) produces the greatest overall performance detriment with the PRO-KOR 556K, though it is a consequence of the combination of internal design and size of the silencer and a key behavioral component of how it achieves the requisite flow rate. Although the full tested length is approximately 6.2 inches with its mount system, the actual silencer core is only 5.4 inches long. As high distal flow rate is a performance goal of the design, the early blast momentum propagation behavior may be viewed as a compromise that is controlled relatively soon after initial jetting. Test measurements indicate that that this early adverse risk is projected forward of the operator. The forward blast load field may therefore be considered relatively “focused” when compared to some other silencers that also possess high distal flow rate.
PEW Science Research Note 2: A relatively unique feature of the JK Armament PRO-KOR 556K is the baffle array layout. The pressure stages are composed of dual-wall baffle pairs with external and interstitial spiral ribbing. Gas expansion and surface area contact is varied progressively and repeatedly down the stack. The measured test data indicates that this design, along with the early venting, results in efficient performance for the length of the silencer. It is interesting to note that the FRP quench shown in Figure 3a favorably results in negligibly elevated risk to personnel during the first shot, throughout the hazard field.
PEW Science Research Note 3: At the time of writing, the measured performance of the JK Armament PRO-KOR 556K places it in the top 5 of the overall MK18 PEW Science Rankings, slightly above the high performance Centurion Arms Maximus-L (6.180). As tested, the Maximus-L is slightly (0.2-in) longer than the PRO-KOR 556K. The JK Armament silencer has relatively balanced performance; its elevated shooter’s ear (operator) Suppression Rating further differentiates it from silencers like the longer solid 556 end cap configuration of the Otter Creek Labs Infinity (6.179), elevating its Composite Suppression Rating. For further context regarding both performance and size balance, the reader is encouraged to use the Suppression Rating Parametric Visualization Tool (Members Only) for independent study.
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. The reader should note that shooting a PRO-KOR 556K indoors and a HUXWRX FLOW silencer indoors may result in different blast overpressure risk profiles.
PEW Science Research Note 5: As in all semiautomatic 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 90 ms in Figure 2a) 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-15 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 7: Note that the muzzle Suppression Rating of the JK Armament PRO-KOR 556K is 39.9 and the at-ear Suppression Rating is 28.7; different zones on the Suppression Rating Dose Chart, but both higher than typical on this weapon system. The lower back pressure of the PRO-KOR 556K, along with its strong muzzle suppression, contributes to a less severe ejection port blast signature, which further decreases shooter hazard on the standard MK18 weapon system. The reader is encouraged to examine the Silencer Hazard Map at the top of this report as detailed in Silencer Hazard Map Brief 8.1.19. Weapon tuning will influence hazard reduction efficacy, and is outside the scope of this study.
The signatures measured at the shooter’s ear are presented and analyzed below.
6.222.2.2 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 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 5. Again, full and shorter timescales are shown.
Figure 4a. JK Armament PRO-KOR 556K 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature
Figure 4b. JK Armament PRO-KOR 556K 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 5a. JK Armament PRO-KOR 556K 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature
Figure 5b. JK Armament PRO-KOR 556K 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature Peaks
The combined high level of muzzle blast suppression and high flow rate from the PRO-KOR 556 silencer is apparent in the above measured test data. Blowdown is expedient which gives way to a relatively short duration blast field (Figure 4) and muzzle blast is shown to overtake ejection port blast in early time, resulting in front-loaded FRP (Fig. 5b). Evidence of blast momentum propagation keeping the JK Armament silencer from achieving the highest levels of performance include:
Higher global blast pressure and impulse amplitude.
Prolonged positive phase impulse accumulation (reference the momentum plateau in Fig. 5b).
PEW Science Research Note 8: For its size, and for the type of technology employed in the silencer, the PRO-KOR 556K performance is exceptional. Though some silencers produce superior blast momentum control, this silencer is “in the mix” when considering the highest levels of performance evaluated on this weapon system. In large part, the novel baffle structure is responsible for this performance. Pressure staging employed by this JK Armament silencer may be accomplished in more complex ways, but the simple “nesting” of adjacent baffles providing ribbed interstitial space provides for efficient pressure staging quickly. In other words, the performance in the length of baffle envelope is higher than typical.
It is important to utilize the presented Silencer Hazard Maps, as available, to understand blast load propagation and human risk variation, spatially, in the free field. As more research is performed, additional simulations near reflecting surfaces will be provided, along with additional member research supplements displaying hazards in the frequency domain.
PEW Science Research Note 9: It is unlikely that the rapid performance advancements showcased in the Standard would happen at this frequency without additive manufacturing. It is not necessarily that many of these technologies would be impossible to implement without 3D printing, but it is likely that rapid prototyping and the removal of some design constraints have greatly accelerated innovation in the space. This JK Armament silencer is a significant technology departure (and potentially performance departure) from their previous offerings.
PEW Science Research Note 10: As evidenced above, the AR-15 weapon system, in general, is extremely hazardous to the weapon operator, even when suppressed. Ejection port blast loads are severe. Tuning of the system by increasing buffer mass, decreasing gas port orifice area, or both, may reduce the amplitude and duration of ejection port blast loads from the weapon chamber. Reduction in severity from such weapon tuning is highly nonlinear and will vary based on silencer and weapon.
6.222.3 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 6 presents a comparison of the PEW Science Suppression Rating of the JK Armament PRO-KOR 556K 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 6. Suppression Rating Comparisons of the JK Armament PRO-KOR 556K and other rifle silencers, Using PEW-SOFT 5.56x45mm Supersonic Test Data and PEW Science Analysis
Figure 6 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. The JK Armament PRO-KOR 556K from this test program is shown in red. 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 and Hazard Map 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. Analytically computed metrics are color-coded in the Rankings Table, in all Silencer Hazard Maps, and keyed to the dose chart for user interpretation.
The following gross conclusions can be made from the metrics presented in Figure 6, above:
The JK Armament PRO-KOR 556K produces free field bystander hazard reduction on par with the following silencers on the MK18 weapon system:
The free field operator (shooter) hazard reduction of the JK Armament PRO-KOR 556K with the standard untuned MK18 weapon system is higher than it is with several other designs due to its higher flow rate (lower back pressure) and its relatively efficient muzzle suppression for its size. The MK18 operator protection with the PRO-KOR 556K is on par with or exceeding that of the:
The top five performing systems on the MK18 showcased in public evaluations overall are:
JK Armament PRO-KOR 556K (6.222); this report
The bottom five performing systems on the MK18 showcased in public evaluations overall are:
PEW Science Research Note 11: Without weapon system tuning, operator hazards from a suppressed MK18, in the free field, plateau at Suppression Ratings near 30. This is due to ejection port blast loads. However, this does not mean that silencers with similar shooter’s ear Suppression Ratings will sound the same to the shooter, in the free field. On the contrary, what an operator hears through the entire time regime of a gun shot event and subsequent environmental reflections, and which acute hazards manifest, may be different. The reader is strongly encouraged to review the published Silencer Hazard Map at the top of this report and in Silencer Hazard Map Brief 8.1.19. Furthermore, to illustrate two extremes, the difference in spatial hazards from a Flow Through silencer and a high back pressure silencer are directly compared in Silencer Hazard Map Brief 8.1.5 (HUXWRX FLOW 556k vs. SilencerCo Saker 556).
As stated in Research Note 3, at the time of writing, the measured performance of the JK Armament PRO-KOR 556K places it in the top 5 of the overall MK18 PEW Science Rankings, slightly above the aforementioned high performance Centurion Arms Maximus-L. As tested, the Maximus-L is slightly (0.2-in) longer than the PRO-KOR 556K. The JK Armament silencer has relatively balanced performance; it’s elevated shooter’s ear (operator) Suppression Rating further differentiates it from silencers like the longer solid 556 end cap configuration of the Otter Creek Labs Infinity (6.179), elevating its Composite Suppression Rating. For further context regarding both performance and size balance, the reader is encouraged to use the Suppression Rating Parametric Visualization Tool (Members Only) for independent study.
Hybrid designs continue to demonstrate significant performance with supersonic ammunition suppression, and silencers like the PRO-KOR 556K, and others, show that performance can be achieved in compact design envelopes. The performance of these next generation systems are significantly elevated when compared to that of highly prolific previous generation hybrids such as the Surefire SOCOM556-RC2 (6.52) and other newly released military silencer hybrids such as the KAC PRT family (6.156) on this weapon system. Users now have additional high performance practical options to reduce weapon system length and maintain hazard reduction.
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 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.
6.222.4 Review Summary: JK Armament PRO-KOR 556K on the MK18 5.56x45mm AR15 with 10.3-in Barrel
When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the JK Armament PRO-KOR 556K with the War Eagle mount achieved a composite Suppression Rating™ of 40.4 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 JK Armament PRO-KOR 556K is a mid- to full-size hard-use 5.56 rifle silencer with very high suppression performance with a balanced flow rate. The silencer is printed from Haynes 282 alloy and uses advanced hybrid geometry to achieve efficient blast propagation control for its size. Blast hazard is projected forward, away from the operator. The silencer is HUB-mount compatible and its end cap is replaceable. This silencer is significantly different from previous modular JK Armament silencer designs and presents an example of the rapid advancement of rifle silencer suppression technology.
The JK Armament PRO-KOR 556K is a relatively advanced hybrid design. Features of note in the silencer include early blast chamber venting, spiral geometry flow shaping features on each baffle with dual cavity baffle walls for pressure staging, and distal circumferential venting. Its removable end cap also possesses venting, though it has considerably less vent area. The 3D-printed internal design features of the PRO-KOR 556K allow it to control blast momentum propagation to a significant degree when compared to many silencers previously evaluated on the MK18 weapon system. The risk field is forward-biased, away from the operator and adjacent bystanders, as illustrated in the Hazard Map at the beginning of this report and in Silencer Hazard Map Brief 8.1.19.
At the time of writing, the measured performance of the JK Armament PRO-KOR 556K places it in the top 5 of the overall MK18 PEW Science Rankings, slightly above the high performance Centurion Arms Maximus-L. As tested, the Maximus-L is slightly (0.2-in) longer than the PRO-KOR 556K. The JK Armament silencer has relatively balanced performance; it’s elevated shooter’s ear (operator) Suppression Rating further differentiates it from silencers like the longer solid 556 end cap configuration of the Otter Creek Labs Infinity, elevating its Composite Suppression Rating. For further context regarding both performance and size balance, the reader is encouraged to use the Suppression Rating Parametric Visualization Tool for independent study.
The PRO-KOR 556K is only 5.4 inches long without a mount. The tested War Eagle flash hider / compensator muzzle device and mount coupler induced extra system length. It is likely that using a shorter direct-thread mount may influence system performance, but the amount of performance degradation is unknown.
The forward printed baffle section of the PRO-KOR 556K is constructed from Haynes nickel-chromium-cobalt alloy and is therefore, like Inconel, expected to offer requisite durability and longevity for aggressive firing schedules. PEW Science has not evaluated the durability of this silencer. As always, the user should remain cognizant of their personal firing schedules. The user should contact JK Armament to ensure compatibility for their use case.
In this review, the JK Armament PRO-KOR 556K 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.
