SSS.6.63 - KGM R30 and the Savage Model 10 PC .308 (Free Version)
/KGM R30 on a Savage Model 10 .308 with 20-in Barrel
The R30 is manufactured by KGM Technologies. It is a 30 caliber centerfire rifle silencer, intended to suppress most cartridges with projectiles appropriately sized to travel through the bore, including 300PRC. It has a 1.75-inch diameter and is 7.5 inches in length when using the direct-thread adapter. The user may choose to use other third-party mount adapters compatible with the 1.375”-24tpi system. The outer tube is Grade 9 titanium and the internal baffle assembly is constructed of Grade 5 titanium. The welded endcap of the R30 possesses 10 circumferential radial vent orifices. This vent array comprises a the so-called KGM Adjustable Port End Cap (APEC); all vents can remain closed or open with the installation and removal of included set-screws. The silencer weighs 13.9 ounces with the direct thread mount and all vents closed. The R30 can be obtained through your local dealer or distributor by contacting KGM Technologies.
PEW Science is an independent private testing laboratory and also the world’s only publicly funded 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 data production for this Sound Signature Review was funded in part by PEW Science Project PEW-KGM-015-001-21. Therefore, data pertaining to the R30 in this Sound Signature Review is published with the express written permission of KGM Technologies, LLC.
This review contains test results using the R30 mounted with the direct thread mount on the Savage Model 10 Precision Carbine rifle, chambered in .308WIN with a 20-inch barrel. Federal XM80 149gr ammunition was used in the test.
Section 6.63.1 contains the R30 test results and analysis with all distal vents closed.
Section 6.63.2 contains the R30 test results and analysis with all distal vents open.
Section 6.63.3 contains a comparison of the sound signatures and flow dynamics of the two configurations.
Section 6.63.4 contains back pressure and Suppression Rating comparisons with selected .30 rifle silencers possessing a PEW Science Back Pressure Metric, Ω in Omega Zone 5 and above. An updated Ω metric chart for the full suite of publicly evaluated .30 rifle silencers is also provided in this section. Further information about the Ω metric and Omega Zones can be obtained in PEW Science Research Supplement 6.40 (Public Article).
Section 6.63.5 contains the review summary and PEW Science opinions.
Summary: When paired with the Savage M10 20” .308 and fired with Federal XM80, the KGM R30 with closed vents, mounted with the direct thread adapter, achieved a Suppression Rating™ of 39.9 in PEW Science testing. With all distal vents open in the same direct thread configuration with the same host weapon and the same ammunition, the KGM R30 achieved a Suppression Rating of 39.3.
Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings
6.63.1 KGM R30 Sound Signature Test Results (Vents Closed)
A summary of the principle Silencer Sound Standard performance metrics of the KGM R30, with all 10 of its distal vents closed, is shown in Table 1. The data acquired 1.0 m (39.4 in) left of the muzzle is available for viewing to all. The data acquired 0.15 m (6 in) right of the shooter’s ear is only available to membership supporters of PEW Science and the Silencer Sound Standard. You can support PEW Science testing, research, and development with a membership, here. State-of-the-art firearm sound signature testing and research conducted by PEW Science is supported by readers like you.
Table 1.KGM R30 (Closed) Sound Metric Summary
6.63.1.1 SOUND SIGNATURES AT THE MUZZLE
Real sound pressure histories 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.
Figure 1 shows a 2.6 millisecond long portion of the first round sound pressure signature of the R30, with all vents closed, as measured 1.0 m left of the muzzle. There are four significant waveform features labeled:
Peak amplitude of internal combustion within the silencer reaches 123.5 dB.
The endcap exit event results in an initial overpressure peak magnitude of 140.0 dB.
The first primary jet builds to an amplitude of 145.8 dB (peak FRP).
Secondary jetting results in a latent peak overpressure amplitude of 147.3 dB.
This is a somewhat typical sequence observed when firing supersonic .308WIN ammunition from a bolt-action rifle with an attached silencer that exhibits moderate flow restriction (back pressure). Internal silencer design can significantly influence the measured timing and pressure amplitudes. Preliminary back pressure comparisons are shown in Section 6.63.4 of this review, with the PEW Science Back Pressure Metric, Ω [Pa-1].
Fig 1. KGM R30 (Closed) First Round Bolt Action Rifle Muzzle Sound Pressure Signature
The waveform shown in Figure 1 possesses characteristics very similar to the FRP signature of silencers exhibiting flow restriction (back pressure) in PEW Science Omega Zone 6, such as the Dead Air Sandman-L (Review 6.23), the CGS Helios QD (Review 6.13), and the Otter Creek Labs PR30S (Review 6.49). Features of sound signatures in this flow regime are characterized by initially decoupled bullet exit events with moderate post-exit amplitude suppression.
At the muzzle, the KGM R30 with its vents closed is slightly quieter than the Dead Air Sandman-L on this platform; the severity of both sound signatures being significantly similar in overall loudness to the human inner ear. In-depth comparisons of the sound signatures from silencers like the R30, Sandman-L, PR30S, and Helios QD are the subject of a future PEW Science Member Research Supplement. It is important to note the Adjustable Port End Cap (APEC) configuration can influence the flow rate and sound signature of the R30. Full venting through the APEC more significantly influences flow rate than signature, particularly at the shooter’s position.
The R30 possesses curved cone notched baffles with progressive venting into annular space. Unique to the R30 are the set-screws in its distal vents, the removal of which drop the PEW Science Omega Metric of the R30 into Zone 5 from Zone 6; see Section 6.63.4 of this review.
Closer views of the first peak of all shots (Fig 2a) and highest peak of the first shot (Fig 2b) are shown below. Figure 2a illustrates the consistency of the internal silencer combustion and endcap exit event between all 5 shots during the test. These waveform feature consistencies in both amplitude and wave shape, from shot to shot, are discernable as a result of the high sample rate and raw, unfiltered data stream from PEW-SOFT. Figure 2b shows points later in time during Shot 1 as the maximum sound pressure occurs from the primary combustion event. Note that the total timescale in Figure 2a is 0.45 milliseconds (450 microseconds) and the total timescale in Figure 2b is only 0.1 milliseconds (100 microseconds). PEW-SOFT provides a sampling point every microsecond and the individual data points are shown in Figure 2b to illustrate this.
Fig 2a. KGM R30 (Closed) Bolt Action Rifle Muzzle Sound Pressure Early-Time Peaks
Fig 2b. KGM R30 (Closed) Bolt Action Rifle Muzzle Sound Pressure Shot 1 Peak
The primary sound signature pressure histories for all 5 shots with the R30 are shown in Figure 3a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 3b, in early time. The real sound impulse (momentum transfer potential) histories from the same 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 and Shot 3.
Fig 3a. KGM R30 (Closed) Bolt Action Rifle Muzzle Sound Pressure Signature
Fig 3b. KGM R30 (Closed) Bolt Action Rifle Muzzle Sound Pressure Signature, Short Time Window
Figure 4a. KGM R30 (Closed) Bolt Action Rifle Muzzle Sound Impulse Signature
Figure 4b. KGM R30 (Closed) Bolt Action Rifle Muzzle Sound Impulse Signature, Short Time Window
The FRP behavior of the R30 in the pressure regime (Figure 3) is easily discernable. After the first shot, secondary jetting is significantly reduced, with the exit event remaining largely uniform. The R30 also exhibits FRP in the impulse regime (Figure 4) but the subsequent reduction is signature is not predicted to be significantly perceptible to bystanders on this platform, until after the third shot, in accordance with PEW Science inner ear modeling.
PEW Science Research Note 1: FRP continuing into the second shot, despite a significant differential in measured Shot 1 impulse, is atypical and a the subject of internal PEW Science research. With its vents closed, the R30 experiences delayed FRP reduction; PEW Science postulates that this may be a consequence of the progressive venting within the silencer not being fully utilized with all of the distal vents closed; flow is postulated to normalize as the vents are opened. See Section 6.63.2 of this review for analysis of test data with all distal vents open.
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 has made a concerted effort to characterize the FRP phenomenon with true physiological human inner-ear response analyses. Additional PEW Science Member Research Supplements containing this information are released periodically.
6.63.2 KGM R30 Sound Signature Test Results (Vents Open)
A summary of the principle Silencer Sound Standard performance metrics of the KGM R30, with all 10 of its distal vents open, 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 6.63.1, the data acquired 0.15 m (6 in) right of the shooter’s ear is only available to membership supporters of PEW Science and the Silencer Sound Standard. You can support PEW Science testing, research, and development with a membership, here. State-of-the-art firearm sound signature testing and research conducted by PEW Science is supported by readers like you.
Table 2.KGM R30 (Vented) Sound Metric Summary
Real sound pressure histories 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 5 shots with the fully-vented R30 are shown in Figure 3a. The sound signatures of Shot 1 and Shot 2 are shown in Figure 3b, in early time. The real sound impulse (momentum transfer potential) histories from the same 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 and Shot 3.
Fig 7a. KGM R30 (Open) Bolt Action Rifle Muzzle Sound Pressure Signature
Fig 7b. KGM R30 (Open) Bolt Action Rifle Muzzle Sound Pressure Signature, Short Time Window
Figure 8a. KGM R30 (Open) Bolt Action Rifle Muzzle Sound Impulse Signature
Figure 8b. KGM R30 (Open) Bolt Action Rifle Muzzle Sound Impulse Signature, Short Time Window
As was shown in the test with the vents closed, the measured pressure regime first-round-pop (FRP) with the vents open is evident when comparing Shot 1 to Shot 2 in both the pressure regime (Figure 7b) and impulse regime (Figure 8b). Note the FRP pressure and impulse differentials are not nearly as significant with the vents open as they are with the vents closed; this is typical behavior resulting from an increase in flow rate and was also observed with the CGS Helios QD (Review 6.13) and its solid and vented endcaps, though the internal gas dynamics of the R30 and Helios QD are significantly different.
PEW Science Research Note 2: Despite the lower differential between FRP in subsequent shots for the open-vent configuration of the R30, the FRP of the R30 with the vents open is more immediately perceptible to bystanders than with the vents closed.
PEW Science Research Note 3: In contrast with the impulse waveforms measured at the muzzle with the distal vents closed (Figure 4a), the initial positive phase impulse slope with the vents open (Figure 8a) is significantly steeper; this is a direct, visual indicator of an increase in flow rate (decrease in back pressure; a lower PEW Science Omega Metric). Waveforms measured for the two configurations are compared in Section 6.63.3 of this review.
Again, the overall shape of the impulse waveforms measured at the muzzle, from shot-to-shot, are extremely consistent, highlighting the silencer’s overall sound performance consistency at the muzzle after the FRP, as well as the relative consistency of the tested firearm configuration. Note that the sound overpressure and impulse measured at the muzzle with the vents open on the R30 are significantly higher than that with the closed-vent configuration, but the Suppression Rating reduction is not. The back pressure is also lower; the silencer drops an Omega Zone. Omega Metric data is presented in Section 6.63.4 of this review.
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.
6.63.3 KGM R30 Distal Vent Configuration Comparison
Below, direct comparisons of the measured pressure and impulse waveforms with the two different vent configurations used in the two tests of the KGM R30 are shown.
Figure 11a and Figure 11b show first-shot muzzle overpressure and impulse comparisons, respectively. These comparisons directly illustrate the changes in gas dynamics at the muzzle due to distal venting from the radial array in the R30 endcap.
Figure 11a. KGM R30 Bolt Action Rifle Muzzle Sound Pressure Signature - Comparison With Vents Closed And Vents Open
Figure 11b. KGM R30 Bolt Action Rifle Muzzle Sound Impulse Signature - Comparison With Vents Closed And Vents Open
The consistency of the tested configurations is highlighted by the extremely similar internal combustion and bullet exit event pressure amplitudes and wave shapes (29.6 ms and 29.7 ms, respectively, Figure 11a). As the primary jet propagates, it is significantly suppressed in the closed-vent configuration and free to vent radially with the vents open (149.7 dB peak, Figure 11a). Subsequent jetting is delayed with the vents closed (146.9 dB, later time, Figure 11a).
The initial rate of rise to maximum positive phase impulse between the two configurations during the first shot is drastically different (Figure 11b). This slope increase, with the vents fully open, is due to faster jetting due to higher flow rate; a reduction in silencer flow restriction. This flow rate correlates with a decrease in backpressure; a lower PEW Science Omega Metric with the vents open. Comparisons with many other 30 caliber silencers on the current market are shown in the section below.
6.63.4 Relative Suppression Rating and Back Pressure Comparisons (.30 Rifle Silencers)
The R30 suppressor is intended to balance sound signature suppression and flow rate (back pressure). PEW Science has developed an empirical relation to quantify the back pressure (flow restriction) of silencers. Figure 12 and Figure 13 show supersonic suppression and back pressure comparisons between selected 7.62mm (30 caliber) rifle silencers shown in public PEW Science Sound Signature Reviews, as of the date of this review publication. The results shown in Figure 7 and Figure 8 are calculated from real test data acquired with PEW-SOFT. Please note the following:
- The PEW Science Back Pressure Metric, Ω [Pa-1], may be generated for any silencer and suppressed weapon system using any suitable raw external overpressure signature data acquired 1.0 m left of the silencer endcap. PEW Science highly recommends data acquisition in accordance with The Silencer Sound Standard.
- Omega Zones are presented in Table 3, below, which are intended to provide guidance to weapons developers, silencer designers, and end-users, with regard to flow restriction characteristics of different silencer designs. It is very important to note that silencers possessing a relatively high Ω can still provide functional use on weapon systems. Some weapon systems are more sensitive to Ω than others.
- It is important to note that a silencer’s Omega Zone can shift when using a mounting scheme that differs from that used in the testing referenced in the published PEW Science Sound Signature Reviews. This phenomenon occurs due to some silencer mounting schemes significantly influencing flow restriction with some silencer designs.
- The theoretical lower limit of flow restriction, or so-called "zero back pressure" would be represented by the unsupressed state, Ω = 0 [Pa-1].
- PEW Science acknowledges that other dynamic events occur within a suppressed weapon system that can also influence weapon function. Therefore, PEW Science acknowledges that Ω is not the sole parameter one must consider for total supppressed weapon system operation. However, PEW Science postulates that the Ω metric influence can be significant.
- The Back Pressure Metric relations are most easily viewed on a logarithmic scale (See Figure 13).
Figure 12. Omega Back Pressure Metric And Suppression Rating Comparisons Of .308 Rifle Silencers Using PEW-SOFT Data And Analysis
As stated above, the PEW Science Back Pressure Metric is most easily viewed on a logarithmic scale. The metric is nonlinear; the shape of the trend in the data presented in Figure 8, below, illustrates the potential thresholds of extreme flow rate (approaching the unsuppressed state) and extreme flow restriction (approaching the trapping of the maximum amount of combustion byproducts in a system).
Figure 13. Omega Back Pressure Metric Comparisons Of .308 Rifle Silencers Using PEW-SOFT Data And Analysis
Omega characterizes silencer back pressure. It is important to note that back pressure is not blow back. The back pressure of a silencer is the flow restriction it introduces to a suppressed weapon system. The blow back phenomenon that can occur during the use of a suppressed weapon system is caused by the reciprocating system actuating too early relative to overpressure decay within the weapon system, resulting in exposure of excessive internal system overpressure to atmosphere. Some weapons may be tuned to function well with silencers in a high Omega Zone. Some weapons may require low-Omega silencers due to constraints in their operating system(s). Omega metric technical details can be found in PEW Science Public Research Supplement 6.40.
Table 3. PEW Science Back Pressure Metric Omega Zones And Suppressed Weapon System Functional Descriptions
The R30 is very similar in Suppression Rating to the Dead Air Sandman-L (Review 6.23) on this test platform. The R30 exhibits slight higher flow restriction (back pressure) than the Sandman-L. Interestingly, the R30 drops a full Omega Zone when all its distal vents are opened. This increase in flow rate (decrease in back pressure; lower PEW Science Omega Metric) results in back pressure behavior similar to the Energetic Armament VOX S (Review 6.3) and SilencerCo Harvester 300 (Review 6.31) but with less severe signature at the shooter’s ear. The vented configuration of the R30 also outperforms the Rugged Surge in its short configuration (Review 6.22) in sound signature suppression at both the muzzle, and at the shooter’s ear, and does so with higher flow rate (lower back pressure). It also maintains higher suppression performance than the Otter Creek Labs PR30S (Review 6.49) with a slightly higher flow rate. The R30 is unable to reach the suppression performance of the CGS Helios QD (Review 6.13), but exhibits a higher flow rate than the Helios QD. The vented configuration of the Helios QD is significantly louder than the vented configuration of the R30. However, the flow rate of the vented Helios QD is also significantly higher than that of the vented R30.
PEW Science Research Note 5: PEW Science urges the reader not to misconstrue a high Omega Metric with absolute use prohibition on semi-automatic systems. Each weapon system may experience varying sensitivity to different Omega Zones and users may exhibit varying preference for weapon system function and operability. The Zones are provided by PEW Science to assist the reader with determination of postulated applicability of silencer types, as some users may only have experience with certain silencers. The Omega Metric is one performance indicator; it allows overall flow rate phenomena to be categorized independently from sound signature suppression performance.
It is extremely important to note that peak sound pressure [dB], peak sound impulse [dB-ms], and Omega (Ω) [Pa-1], alone, do not determine the sound supression performance of a silencer. It is the combination of these and other waveform parameters that form the total sound signature and the influence on human inner ear response. The Suppression Rating computation considers all of these factors.
6.63.5 Review Summary: KGM R30 on a Savage Model 10 .308 with 20-in Barrel
When paired with the Savage M10 20” .308 and fired with Federal XM80, the KGM R30 with closed vents, mounted with the direct thread adapter, achieved a Suppression Rating™ of 39.9 in PEW Science testing. With all distal vents open in the same direct thread configuration with the same host weapon and the same ammunition, the KGM R30 achieved a Suppression Rating of 39.3.
PEW Science Subjective Opinion:
The KGM R30 is a mid-size .30 rifle silencer that exhibits balanced sound signature reduction and flow rate (back pressure), while possessing a modular rear mount capability. Note that the R30 contains adjustable radial vents on its endcap, adding to the system’s versatility.
The practice of using of distal vent arrays to allow higher flow rate through silencers is relatively common. The placement of the vents to produce radial thrust may influence weapon system kinematics. As intended, these systems may influence recoil dynamics, specifically. The kinematic influence of such systems has not been evaluated by PEW Science. The combination of radial external venting with internal coaxial elements is relatively uncommon. PEW Science postulates that the coaxial elements and progressive internal venting contribute significantly to the sound suppression performance of the R30 and its sister silencer, the R556.
The increase in flow rate (reduction in back pressure) when fielding the KGM R30 with its distal vent array fully open, is measurable. The subsequent reduction in Suppression Rating in the vented configuration being moderate to minimal, is notable. This adaptability without significant sacrifice of sound suppression performance, may be attractive to some users.
The rear mount threading of the R30 is 1.375”-24tpi; relatively common in today’s rifle silencer market. As a result of this common modular interface, a plethora of mounting systems may be used. The performance of the R30 may be influenced by mounting system choice. The user’s choice of mount may balance system weight, length, durability, utility, and even back pressure of the silencer. The data presented by PEW Science in this Sound Signature Review was measured with the direct-thread mount. The mount may be removed with an included spanner tool from KGM. Note that although the end cap possesses adjustable radial vents, the end cap itself is not removeable.
PEW Science has not evaluated the durability of the R30 on semiautomatic or automatic host weapons. The user is encouraged to contact the silencer manufacturer to determine appropriate firing schedule.
In this review, the R30 performance metrics depend upon suppressing a supersonic centerfire rifle cartridge; no easy 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 .308WIN cartridge are significant; the measured pressure and impulse magnitudes, and their durations, illustrate this fact.
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.
