SSS.6.66 - CGS Helios QD and the MK18 5.56x45mm Short Barrel Automatic AR15 Rifle
/CGS Helios QD on the MK18 5.56x45mm AR15 with 10.3-in Barrel
The Helios QD is designed by CGS Group. It is a centerfire rifle silencer intended for use on semiautomatic and automatic 5.56 mm host weapons, but possesses a bore larger than 30 caliber and can suppress many cartridges, up to and including .300 Remington Ultra Magnum, with no barrel length restrictions. It has a 1.75-inch diameter and is 7.2 inches long. The silencer mounts to the host firearm with several available mounting schemes compatible with the 1.375”-24tpi system, including direct-thread. An adapter ring is included to convert the rear female thread to use third-party adapters that possess additional length. The user may choose from two included end-caps; a solid and vented version. The main silencer body is constructed from 718 Inconel using additive manufacturing (DMLS 3D printing). The end-caps and mounts are constructed from heat treated 17-4 stainless steel. The silencer weighs 22.7 ounces with the 1/2”-28tpi direct-thread adapter installed. The Helios QD can be obtained from Silencer Shop.
This review contains results from two separate tests. PEW Science tested the Helios QD on the MK18 with both the solid end cap and vented end cap. As the internal baffle geometry is fully integrated with the silencer body and the silencer possesses linked coaxial internal flow path geometry that is utilized differently based upon end-cap selection, the gas dynamics change significantly with endcap selection. Similar phenomena were measured and analyzed in the PEW Science test of the CGS Helios QD on a bolt-action rifle in Sound Signature Review 6.13.
Both sets of test results in this Sound Signature Review are of the Helios QD on the MK18 Automatic AR15 rifle, chambered in 5.56x45mm NATO with a 10.3-inch barrel. Federal XM193 55gr ammunition was used in the tests. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Section 6.66.1 contains test results using the solid end cap.
Section 6.66.2 contains test results using the vented end cap.
Section 6.66.3 contains Suppression Rating comparisons of the two systems, along with comparisons with dedicated 223 and 30 caliber silencers on the current market, including the Surefire SOCOM556-RC2, OSS HX-QD 556, Q Trash Panda, and others.
Section 6.66.4 contains the review summary and subjective PEW Science opinions.
Summary: When paired with the 10.3-in barrel MK18 and fired with Federal XM193, the CGS Helios QD, mounted with direct-thread and equipped with the solid end cap, achieved a composite Suppression Rating™ of 27.1 in PEW Science testing. When equipped with the vented end cap on the same host weapon and fired with the same ammunition, the Helios QD achieved a composite Suppression Rating of 24.5. As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
The supersonic .308 performance of the CGS Helios QD is detailed in previous Sound Signature Review 6.13, in which it achieved a Suppression Rating of 44.5.
Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings
6.66.1 Helios QD Sound Signature Test Results (Solid End Cap)
A summary of the principle Silencer Sound Standard performance metrics of the Helios QD tested with the solid end cap 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. CGS Helios QD (Solid End Cap) Sound Metric Summary
6.66.1.1 SOUND SIGNATURES AT THE MUZZLE
Real sound pressure histories from a 6-shot test acquired with PEW-SOFT™ are shown below. Six cartridges were loaded into the magazine, the fire control group positioned to single-shot, and the weapon was fired until the magazine was empty and the bolt locked back on the follower of the empty magazine. Only five shots are considered in the analysis. The signatures of Shot 6 are displayed in the data presentation but are not included in the analysis to maintain consistency with the overall PEW Science dataset and bolt-closing signatures. The waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz). The peaks, shape, and time phasing (when the peaks occur in relation to absolute time and to each other) of these raw waveforms are the most accurate of any firearm silencer testing publicly available. PEW-SOFT data is acquired by PEW Science independent testing; the industry leader in silencer sound research. For more information, please consult the Silencer Sound Standard.
The primary sound signature pressure histories for all 6 shots with the Helios QD are shown in Figure 1a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 1b, in early time. The real sound impulse (momentum transfer potential) histories from the same 5-shot test are shown in Figure 4a. In Figure 4b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shot 2.
Fig 1a. CGS Helios QD (Solid End Cap) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 1b. CGS Helios QD (Solid End Cap) 5.56x45mm NATO MK18 Automatic Rifle Sound Pressure Signature
Figure 2a. CGS Helios QD (Solid End Cap) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 2b. CGS Helios QD (Solid End Cap) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 1b displays clear decoupling between initial bullet exit, gas jetting, and the primary jet in which peak first-round-pop (FRP) resides. The measured FRP is visible in both the pressure and impulse regimes, in peak amplitudes, timing, and wave shapes, as is typical from a suppressed rifle. It should be noted that the FRP measured at the muzzle from the Helios QD is not significant on the MK18; bystanders may perceive subsequent shots to be louder than the first shot.
PEW Science Research Note 1: The CGS Helios QD is an over-bored 30 caliber rifle silencer (0.36-in, increasing to 0.375-in at the exit aperture), and as such, is significantly over-bored for the 5.56x45mm weapon platform. The bore of the Helios QD is so large that it can suppress the .338LM cartridge (though this is not recommended by the manufacturer due to possible alignment issues). Somewhat erratic impulse behavior and relatively high rate of rise to maximum peak positive phase impulse (Figure 2a) is characteristic behavior of such a silencer used on the MK18. While the excessively large bore diameter does result in a high mass flow rate (low back pressure; low PEW Science Omega Metric) on the platform, the Helios QD is also able to route gas to an alternate path; its outer annulus. The aforementioned initial jet decoupling from the Helios on the MK18 is in contrast with the early time behavior observed from other 30 caliber silencers tested on the MK18 platform, such as the Rugged Razor (Review 6.58) and Q Trash Panda (Review 6.61). Those silencers have more significant early-time jetting, despite the Helios QD possessing an even larger bore. However, inside the Helios QD, the initial gas jet, after bullet uncorking from the barrel muzzle, must travel to the annular vents to utilize the annular space in early time. Though delayed, this path does direct some gas away from the primary oversized bore. It is this behavior, along with other internal features, that enable the Helios QD to restrict slightly more flow than the Rugged Razor on this host weapon system, despite the larger bore of the Helios QD. The Q Trash Panda restricts more flow than both silencers on this weapon system.
PEW Science Research Note 2: CGS rifle silencers, while sharing some similarities, possess differing design features across model lines. For example, the full-size CGS Hyperion (Review 6.27), short CGS Hyperion K (Review 6.28), and CGS Helios DT (analysis not yet published by PEW Science) possess similar geometry routing gas to the outer annulus in early time after muzzle uncorking. However, the CGS Helios QD’s geometry is different. The gas path is more arduous; the time delay between primary jet formation and annulus travel is greater than in the Hyperion series. Note that the Helios DT is, other than mount threading, identical to the Hyperion K. The Helios DT is not the same silencer as the Helios QD, in mounting scheme or internal geometry.
When examining the performance with 7.62x51mm NATO ammunition from a 20-inch barrel in the aforementioned reviews, both the Helios QD (Review 6.13) and the Hyperion K heavily utilize their respective annular spaces; the Helios QD provides a longer gas path, and higher flow restriction (higher back pressure; higher PEW Science Omega Metric) than the Hyperion K. When the input loading changes to 5.56x45mm NATO ammunition from a 10.3-inch barrel, the behavior of the two designs also changes. PEW Science postulates that the smaller jet diameter and differing jet duration from the 5.56 cartridge results in a significant flow divergence; the proportion of primary jetting traveling down the primary bore becomes greater in the Helios QD than in the Hyperion K. Therefore, PEW Science postulates that the Helios QD may exhibit an initial annular gas path that is too long in relation to primary bore diameter for efficient operation on the MK18 weapon platform. Whereas the flow state of the Hyperion K becomes saturated earlier than that of the Helios QD in the 7.62x51mm NATO tests, the 5.56x45mm NATO short barrel tests do not exercise the internal envelope of the Helios QD to the same degree. The inflection point of flow divergence; the so-called tipping-point of combustion jet diameter, pressure, and duration, in which the Helios QD’s annular path becomes more favorable, is the subject of future PEW Science research. PEW Science further postulates that in addition to the inflection point being a function of uncorking pressure and combustion duration, it may also be influenced by muzzle orifice proximity to the blast baffle in the Helios QD. The performance of the CGS Helios DT (Hyperion K) on the MK18 is the subject of a future PEW Science Sound Signature Review.
PEW Science Research Note 3: While it is common for some silencer designs to have relatively different performance across various flow regimes, it is uncommon for a silencer to exhibit such high sensitivity to the aforementioned parameters in Research Note 2. The impact of cartridge choice, barrel length, and the balance of geometric parameters in the Helios QD design for most efficient operation, is a potential subject of future research. PEW Science postulates this case study is applicable to many designs that rely on annular gas flow, though there are features of the Hyperion technology in the Helios QD that may exacerbate the sensitivity of some parameters.
PEW Science Research Note 4: While a second pressure pulse originates from the ejection-port signature of the weapon, it occurs early enough in time such that its waves coalesce with that of the muzzle signature. However, in late time (at approximately 85 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 MK18 bolt is directly related to the flow restriction of a silencer for a given weapon system. PEW Science has determined bolt closing time variation from the unsuppressed state to be a reliable indicator of silencer back pressure, with strong correlation with the PEW Science Back Pressure Metric, Omega. However, PEW Science has also determined that the indicator is unreliable upon upper receiver fouling. Sound signatures are not influenced by this fouling, as these kinematics occur in late time, after gas venting to atmosphere. Momentum transfer, weapon condition (upper receiver fouling), and other factors, can significantly influence bolt closing time. PEW Science urges the reader to exercise extreme caution if using the published bolt closing time to make determinations regarding silencer flow restriction (back pressure) or weapon system kinematics. This type of calculation may provide erroneous results, as the weapon condition at the time of each test is not published data. The time-scale duration showing bolt closing time is only published by PEW Science such that the signature data pedigree may be verified.
The shape, timing, and magnitudes of the early-time pressure pulses and overall shape of the impulse waveforms measured at the muzzle, from shot-to-shot, are relatively consistent. The consistency of the waveform amplitudes highlight the silencer’s overall sound performance consistency at the muzzle after the FRP, as well as the relative consistency of the tested automatic rifle firearm configuration.
As typically indicated, first-round sound signatures always differ from subsequent shots, as the atmosphere within the silencer changes. The FRP phenomenon cannot always be shown by viewing only the peak sound pressure. This is one of the reasons why The Silencer Sound Standard requires examining multiple sound signature metrics. Ammunition consistency can play a role in the determination of FRP, however, the close examination of measured pressure and impulse waveforms typically excludes ammunition from the possible factors influencing true FRP, due to the relative consistency of most high quality factory ammunition.
Note that the muzzle Suppression Rating of the CGS Helios QD with its solid end cap is 24.7 and the at-ear Suppression Rating is 22.3; the same zone on the Suppression Rating Dose Chart. The high flow rate of the CGS Helios QD assists with reducing ejection port signature, but its muzzle signature is severe enough to increase the overall severity of the signature to the shooter. The use of the vented end cap changes the gas dynamics, and thus the suppression performance, of the Helios QD on this platform. This phenomenon is explored in Section 6.66.2 of this review.
6.66.1.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 6-shot test acquired with PEW-SOFT at the shooter’s ear are shown below. Again, the waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz).
The primary sound signature pressure histories at the ear for all 5 shots are shown in Figure 3. The primary sound signature history is shown on the left. A zoomed-in timescale is displayed on the right, in the region of peak sound pressure for Shot 1 and Shot 2. The real sound impulse (momentum transfer potential) histories at the ear from the same 5-shot test are shown in Figure 4. Again, full and short timescales are shown.
Figure 3a. CGS Helios QD (Solid End Cap) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature
Figure 3b. CGS Helios QD (Solid End Cap) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 4a. CGS Helios QD (Solid End Cap) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature
Figure 4b. CGS Helios QD (Solid End Cap) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature Peaks
Unlike in the measurements at the muzzle, the FRP from the Helios QD at the shooter’s ear is significant enough to be immediately noticeable to the shooter. Like in the measurements at the muzzle, there are waveform indicators measured at the ear consistent with low back pressure (low flow restriction; low PEW Science Omega Metric). The erratic impulse behavior from significant over-bore and an under-utilized annulus remains.
Significant difference at the shooter’s ear is noted in the behavior between the CGS Helios QD and the Rugged Razor and Q Trash Panda on the MK18. Like noted at the muzzle, there is erratic impulse behavior, indicative of significant silencer over-bore. However, the variation is not as significant with the Helios QD as it is with the Razor and Trash Panda. This greater consistency, despite an even larger bore, is again postulated to result from flow traveling to the annular gas path, despite its under-utilization discussed in the previous section. Notably, the secondary combustion phenomena from the short (10.3-in) MK18 host weapon barrel is suppressed effectively. Research Supplement 6.51 illustrates this secondary blast, unsuppressed in the free field. Note that this secondary blast may not always be as effectively suppressed with the vented end cap (See Section 6.66.2 of this review, below).
PEW Science Research Note 6: Shorter than the 20-in barrel bolt-action rifle host weapon, the 10.3-in barrel automatic rifle places the blast source in closer proximity to the shooter’s ear. In addition to the silencer endcap being closer, the ejection port allows combustion products at higher than atmospheric pressure to vent relatively suddenly in the time regime of so-called chamber blow-down. This venting time, and thus the vented pressure amplitude and wave shape, varies depending upon the pressure history in the chamber and barrel, which are in turn dependent upon the flow restriction (back pressure) of the silencer. Both the close proximity of the muzzle to the shooter’s ear, and the additive ejection port pressure coalescing with the muzzle signature wave front(s), result in a more severe signature at the shooter’s ear than 1.0 m left of the weapon muzzle. Therefore, the at-ear Suppression Rating is lower than the muzzle Suppression Rating with this particular silencer on the MK18 host weapon.
Data acquired with the vented end cap follows.
6.66.2 Helios QD Sound Signature Test Results (Vented End Cap)
A summary of the principal Silencer Sound Standard performance metrics of the Helios QD tested with the vented end cap 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 stated in Section 6.66.1, 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. CGS Helios QD (Vented End Cap) Sound Metric Summary
6.66.2.1 SOUND SIGNATURES AT THE MUZZLE
Real sound pressure histories from the second 6-shot test with the Helios QD acquired with PEW-SOFT™ are shown below, this time with the vented end cap. 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 sixth shot signatures are displayed in the data presentation but are not included in the analysis to maintain consistency with the overall PEW Science dataset and bolt-closing signatures. The waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz). The peaks, shape, and time phasing (when the peaks occur in relation to absolute time and to each other) of these raw waveforms are the most accurate of any firearm silencer testing publicly available. PEW-SOFT data is acquired by PEW Science independent testing; the industry leader in silencer sound research. For more information, please consult the Silencer Sound Standard.
The primary sound signature pressure histories for all 6 shots with the Helios QD with the vented end cap 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 and also Shot 4.
Fig 5a. CGS Helios QD (Vented End Cap) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Pressure Signature
Fig 5b. CGS Helios QD (Vented End Cap) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 6a. CGS Helios QD (Vented End Cap) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
Figure 6b. CGS Helios QD (Vented End Cap) 5.56x45mm NATO MK18 Automatic Rifle Muzzle Sound Impulse Signature
The gross pressure amplitudes (Figure 5a) and impulse amplitudes (Figure 6a) are higher with the vented end cap than with the solid end cap due to a higher flow rate from the silencer; the gas from the annulus is directly vented, along with additional primary bore venting. Significantly similar early-time behavior is noted in pressure space (Figure 5b), with the positive phase duration increasing, consistent with higher flow rate. With the vented end cap, FRP at the muzzle is significant. This is in contrast with the silencer’s behavior at the muzzle with its solid end cap. PEW Science postulates this is due to the higher flow rate through the annulus with the vented end cap and its linkage with the main baffle geometry in the mid-section of the silencer.
A significant event that was not present in the solid end cap test is the secondary combustion propagation from the vented end cap during Shot 4 (Figure 6b). The timing of the secondary maximum (142.5 dB-ms) is consistent with secondary combustion phenomena from the 10.3-in barrel MK18. PEW Science postulates this secondary combustion may have been facilitated by the higher flow rate with the vented end cap; the same phenomenon that results in more significant muzzle FRP. Similar behavior was noted in the test of the Rugged Razor (Review 6.58) and even more significantly in the test of the Q Trash Panda (Review 6.61) on the MK18 weapon system. As discussed in Section 6.66.1.1 of this review, the secondary combustion remains suppressed with the solid end cap.
The consistency of the silencer in the tested configuration, despite the erratic secondary combustion in Shot 4, is highlighted by the initial impulse slopes in Figure 6a and also by the coincident rarefaction event shown in Figure 5b. During Shot 1 and Shot 2, the primary initial positive phase (the initial major jetting) ends at a similar time. This behavior occurring in a high flow rate silencer is indicative of consistent flow. High flow rate silencers exhibiting similar consistency include those from OSS. High flow rate phenomena with less consistency has been observed in first-generation Griffin Armament ECO-FLOW baffles in the Explorr, for example.
PEW Science Research Note 7: PEW Science postulates that the erratic combustion behavior in Figure 6 may be uncharacteristic of the Helios QD with 5.56x45mm use through longer barrels (See Research Notes 2 and 3, above). Without secondary burning, the bore aperture and annulus may result in more normalized flow, as measured in 20-in .308 testing of the Helios QD (Review 6.13). Investigation of this phenomenon is the subject of future testing and analysis.
6.66.2.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 6-shot test of the Helios QD with the vented end cap 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 with the Helios QD are shown in Figure 7a. A zoomed-in timescale is displayed in Figure 7b, in the region of peak sound pressure for Shot 1, Shot 2, and Shot 4. The real sound impulse (momentum transfer potential) histories at the ear from the same 6-shot test are shown in Figure 8. Again, full and short timescales are shown.
Figure 7a. CGS Helios QD (Vented End Cap) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature
Figure 7b. CGS Helios QD (Vented End Cap) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Pressure Signature, Short Time Window
Figure 8a. CGS Helios QD (Vented End Cap) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature
Figure 8b. CGS Helios QD (Vented End Cap) 5.56x45mm NATO MK18 Automatic Rifle Ear Sound Impulse Signature Peaks
Unlike at the muzzle, and in a reverse trend to the use of the solid end cap, the use of the vented end cap with the Helios QD does not result in significant FRP to the shooter on the MK18. PEW Science postulates this is the result of the extremely high flow rate of the vented configuration of the silencer and the ejection port signature remaining as an additive event to shooter perception. Another consequence of the high flow rate is significantly more consistent impulse waveforms at both the muzzle and ear. Despite the inner ear response not significantly increasing after the first shot in this configuration, FRP phenomena is still measurable in both pressure and impulse space and the secondary combustion phenomenon is again plainly visible (Figure 8b).
PEW Science Research Note 8: Note that the secondary combustion phenomenon in Shot 4 is so pronounced that it induces a secondary ground reflection in late time (Figure 7b). The 5.56x45mm cartridge was not designed to be fired from a 10.3 inch barrel. Nonetheless, the overall signature is significantly suppressed. PEW Science inner ear modeling indicates that Shot 4 is actually one of the quietest shots to the shooter in this test, which may be the result of prolonged positive phase pressure inducing a significant negative phase (rarefaction) delay, which changes the interaction of the muzzle signature and ejection port signature. Rapid transition to negative phase can exacerbate ear response. The impact of this phenomenon on the human inner ear is the subject of ongoing PEW Science research.
6.66.3 Suppression Rating Comparison (5.56x45mm from the MK18)
Figure 9 presents a comparison of the PEW Science Suppression Rating of the CGS Helios QD to that of other 30 caliber silencers and 223 caliber rifle silences on the MK18 automatic AR15 rifle. The standard PEW Science MK18 test host weapon system is described in Public Research Supplement 6.51.
Figure 9. Suppression Rating Comparisons with the CGS Helios QD and other silencers, Using PEW-SOFT 5.56x45mm Supersonic Test Data
From the above data, it can be concluded that the significant over-bore of the CGS Helios QD is detrimental to its overall sound suppression performance on the MK18 weapon system. While the bore size significantly increases the flow rate (reduces the back pressure; reduces the PEW Science Omega Metric on the platform), it does so at the expense of signature severity to the shooter’s ear. The barrel length of the MK18 is short, and the aforementioned phenomena of gas flow divergence within the Helios QD creates an environment in which the severe jetting may favor the primary bore path. The at-ear signature, as a result, suffers; the signature to which the shooter’s ear is subjected is a function of both ejection port and muzzle signature. When the silencer’s endcap is in closer proximity to the shooter, the severity is increased. This phenomenon is observed in other over-bored silencers such as the Rugged Razor (6.58). Interestingly, the Helios QD has slightly higher performance than the Q Trash Panda (6.61) at the shooter’s ear on this platform. PEW Science postulates this is due to the higher flow restriction (higher back pressure) of the Q Trash Panda on the MK18. The higher back pressure of the Q Trash Panda on the MK18 than the Helios QD (the reverse relationship to that observed in the 20-in 7.62x51mm bolt action tests) is not necessarily a function of cartridge; it is a function of the variable behavior of the Helios QD with the aforementioned parameters in Research Note 2, Section 6.66.1.1. The aforementioned gas flow divergence into the main bore, not reaching the annulus quickly enough on this platform, results in different flow dynamics; the Helios QD may possess a higher flow rate on short barrel 5.56x45mm host weapons. This behavior occurs even with the solid end cap.
The coalescing of the ejection port overpressure with the primary muzzle blast exacerbates the severity of the signature at the shooter’s head position. It is not ejection port signature, alone, that dictates the signature measured at the shooter’s head position.
PEW Science Research Note 9: The vented configuration of the Helios QD is louder than the configuration with the solid end cap on the MK18. However, the aforementioned under-utilization of the annulus on this platform plays a significant role in the vented end cap signature not being nearly as severe, relative to that with the solid end cap, as compared to the previous 7.62x51mm NATO bolt action tests with the Helios QD (6.13). The comparative data in Figure 9 illustrates that the inherent functionality of the Helios QD may not be fully applicable for the MK18; the increase in flow rate with the use of the vented end cap is measurable but the utility may be less than ideal. PEW Science postulates that the Helios QD functionality, holistically, is best applied to weapon systems with larger diameter, longer duration jetting in the high pressure regime, and systems in lower pressure regimes. Rifle silencer application-dependent suitability is not without precedent; for example, many rifle silencers without annular gas paths or early venting are best suited for lower pressure or shorter duration flows (Q Trash Panda, Thunder Chicken, the Rugged series, Dead Air Sandman series, etc). There are also silencers that may excel in multiple flow regimes (the CGS Hyperion and Dead Air Nomad series).
The CGS Helios QD produces a signature at the shooter’s ear on the MK18 that is on-par with that produced from the 3-Prong equipped Surefire SOCOM556-RC2 (Review 6.52). However, at the muzzle, the Surefire silencer is significantly quieter on this platform, at over a Suppression Rating category higher than the Helios QD. The WARCOMP-equipped Surefire silencer exhibits poor shooter’s ear performance, but still higher performance to bystanders than the Helios QD on the MK18.
The two silencers from HUXWRX; the OSS HX-QD 556 (6.54) and OSS HX-QD 556k (6.64) both exhibit higher shooter’s ear performance than the Helios QD, regardless of which end cap is used. The full-size OSS silencer also possesses a less severe signature at the muzzle on the MK18.
6.66.4 Review Summary: Helios QD 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 CGS Helios QD, mounted with direct-thread and equipped with the solid endcap, achieved a composite Suppression Rating™ of 27.1 in PEW Science testing. When equipped with the vented end cap on the same host weapon and fired with the same ammunition, the Helios QD achieved a composite Suppression Rating of 24.5. As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Subjective Opinion:
The CGS Helios QD is a full-size machine gun silencer when compared to the size of typical 5.56mm rifle silencers. However, the bore tapers from 0.36-in to 0.375-in at the exit, allowing safe use with 30 caliber projectiles and potential use with even larger projectiles. In addition to the 3D-printed Inconel version of the silencer, a 3D-printed titanium version is available that significantly reduces the system weight.
Significant over-bore for the 5.56x45mm platform, coupled with unique internal geometry, moderately lowers the sound suppression performance of the Helios QD with short barrel 5.56x45mm weapons like the MK18. The inflection point of flow divergence; the so-called tipping-point of combustion jet diameter, pressure, and duration, in which the Helios QD annular path becomes more favorable, is the subject of future PEW Science research. PEW Science further postulates that the inflection point is a function of uncorking pressure, combustion duration, and can also be influenced by muzzle orifice proximity to the blast baffle in the Helios QD. The Helios DT / Hyperion K behave differently. The performance of the CGS Helios DT on the MK18 is the subject of a future PEW Science Sound Signature Review.
The silencer has changeable end-caps; the user can choose between higher sound suppression (solid end-cap configuration) and lower sound suppression with lower back pressure (vented end-cap configuration). Interestingly, the Helios QD exhibits lower relative flow restriction on short barrel 5.56x45mm host weapons than longer barrel 7.62x51mm host weapons, compared with some other designs. This phenomenon is the subject of ongoing PEW Science research.
Tolerance stacking with variable end-caps is sometimes an issue. However, as the Helios QD is 3D printed, it is possible that manufacturing tolerances of the “core” section may be controlled more easily than in traditional manufacturing; PEW Science does not anticipate any issues. The repeatability, concentricity, and general alignment of 3D printed designs and their interface with machined parts is a subject of continued research interest. As 3D-printed parts continue to be introduced into silencer component manufacturing, designs are expected to evolve.
The Helios QD possesses tapered interfaces at threaded connections to assist with alignment and fastening. This assists with retention of the end-caps and the mount interfaces. The ability to use a socket to tighten and loosen the end-caps is a welcome convenience. It is important to note that in addition to the two end-caps, the silencer includes two direct thread mounts and a QD adapter to interface with the 1.375”-24tpi mount system. Therefore, depending on the muzzle device length, the Helios QD may be used with various third-party mounting systems.
The internal baffle geometry of the Helios QD is patented and referred to as Hyperion Technology, present in all CGS rifle silencers. The blast chamber vents flow into two primary directions; a main axial flow path and a coaxial outer flow path (the vent path is longer, however, than in the Hyperion series and Helios DT). The utilization of the coaxial chamber is unique, in that main axial flow is introduced into existing coaxial flow approximately halfway forward of the blast baffle. In addition to this secondary flow introduction, the coaxial chamber may be vented to atmosphere at the forward section of the silencer by using the vented end-cap. The vented end-cap significantly changes the functionality of the silencer. It is important to note that the vented flow with the vented end-cap originates from the coaxial chamber but also possesses increased primary bore vent area.
The Helios QD is extremely durable and has undergone a significant amount of automatic and semi-automatic sustained fire testing by CGS on 5.56mm barrels as short as 5 inches and on belt-fed weapons with no apparent damage. Interested parties are encouraged to contact CGS for more information on such third-party testing. The Helios QD has no barrel length restrictions or firing schedule restrictions. The titanium version of the silencer, however, does have restrictions.
In this review, the Helios QD 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.
