SSS.6.81 - Otter Creek Labs Hydrogen-L and the Savage Model 10 PC .308 (Free Version)
/Otter Creek Labs Hydrogen-L on a Savage Model 10 .308 with 20-in Barrel
The Hydrogen-L is designed and manufactured by Otter Creek Labs. It is a 30 caliber centerfire rifle silencer, intended to suppress most cartridges with projectiles appropriately sized to travel through the bore, including 300 Remington Ultra Magnum. It has a 1.625-inch diameter and is 9 inches long. The total length with the included direct thread adapter is 9.4 inches. The user may choose to use third-party adapters compatible with the 1.375”-24tpi system. The silencer is tubeless and all welded components are Grade 5 titanium. The silencer weighs 11.9 ounces, and the included direct thread mount weighs 1.9 ounces, for a total system weight of 13.8 ounces, as tested. The Hydrogen-L can be obtained from Otter Creek Labs Dealers.
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-OCL-025-001-22. Therefore, data pertaining to the Hydrogen-L in this Sound Signature Review is published with the express written permission of Otter Creek Labs, LLC.
This review contains single-test results using the Hydrogen-L 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 tests.
- Section 6.81.1 contains the Hydrogen-L test results and analysis.
- Section 6.81.2 contains back pressure and Suppression Rating comparisons with selected .30 rifle silencers possessing a PEW Science Back Pressure Metric, Ω [Pa-1] 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 6.81.3 contains the review summary and PEW Science opinions.
Summary: When paired with the Savage M10 20” .308 and fired with Federal XM80, the Otter Creek Labs Hydrogen-L, mounted with direct thread, achieved a Suppression Rating™ of 49.8 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
6.81.1 Otter Creek Labs Hydrogen-L Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the Hydrogen-L 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. Otter Creek Labs Hydrogen-L Sound Metric Summary
6.81.1.1 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 2.5 millisecond long portion of the first round sound pressure signature of the Hydrogen-L as measured 1.0 m left of the muzzle. There are five significant waveform features labeled:
Peak amplitude of internal combustion within the silencer reaches 124.9 dB.
The end cap exit event results in an initial peak magnitude of 140.4 dB, which is also peak FRP.
Secondary jetting occurs at an amplitude of 133.0 dB.
Jetting decays to a low amplitude of 119.2 dB.
Low amplitude jetting continues until later time, at which a peak of 138.5 dB is reached. See Figure 3b.
This is a somewhat typical sequence observed when firing supersonic .308WIN ammunition from a bolt-action rifle with an attached silencer that exhibits high flow restriction (back pressure). Internal silencer design can significantly influence the measured timing and pressure amplitudes. Preliminary back pressure comparisons are shown in Section 6.81.3 of this review, with the PEW Science Back Pressure Metric, Ω [Pa-1].
Fig 1. Otter Creek Labs Hydrogen-L First Round Bolt Action Rifle Muzzle Sound Pressure Signature
The waveform shown in Figure 1 possesses early time characteristics very similar to the FRP signature of silencers exhibiting flow restriction (back pressure) in PEW Science Omega Zone 7, such as the Dead Air Nomad-L (Review 6.55), the CGS Hyperion (Review 6.27), the Diligent Defense Enticer-L (Review 6.67), the Thunder Beast ULTRA 9 (Review 6.24), and the Otter Creek Labs PR30L (Review 6.48). Features of sound signatures in this flow regime are characterized by highly decoupled bullet exit events with extreme post-exit amplitude suppression. This behavior is directly indicative of the extreme flow restriction of such silencers. Like the above silencers, the Hydrogen-L exhibits a significant peak amplitude delay on this platform. The silencer also exhibits extreme sound signature suppression performance in a lightweight envelope.
The Otter Creek Labs Hydrogen-L uses a somewhat traditional stepped cone without separate annular space. As the silencer is tubeless, this relatively simple geometry allows the Hydrogen-L to exhibit significant weight savings while maintaining adequate strength for magnum rifle cartridges. Despite the simple baffle design, the sound suppression performance of the Hydrogen-L is significant. The high performance of the silencer is due to a combination of the baffle design, their number, and its length. Nearing the Composite Suppression Rating 50 Zone on this host weapon, the Hydrogen-L exhibits performance close to that of more complex designs such as the Enticer-L, Nomad-L, and Hyperion, all of which utilize at least some venting to outer annular space. The Hydrogen-L bridges the gap between next-generation silencers and conventional performance in the design envelope. It should be noted that the diameter of the silencer is 1.625 inches; the same diameter as the Enticer-L.
Closer views of the first peak of all shots (Fig 2a) and highest peak of the first shot (Fig 2b) are shown below. In this test, it is coincidental that the first peak of Shot 1 is also peak FRP. Often times, this is not the case. Figure 2a illustrates the relative consistency of the internal silencer combustion and end cap exit event between all 5 shots during the test. These waveform feature consistencies in both gross 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 0.48 milliseconds (480 microseconds) and the total timescale in Figure 2b is only 0.08 milliseconds (80 microseconds). PEW-SOFT provides a sampling point every microsecond and the individual data points are shown in Figure 2b to illustrate this.
Fig 2a. Otter Creek Labs Hydrogen-L Bolt Action Rifle Muzzle Sound Pressure Early-Time Peaks
Fig 2b. Otter Creek Labs Hydrogen-L Bolt Action Rifle Muzzle Sound Pressure Shot 1 Peak
The primary sound signature pressure histories for all 5 shots with the Hydrogen-L 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. Otter Creek Labs Hydrogen-L Bolt Action Rifle Muzzle Sound Pressure Signature
Fig 3b. Otter Creek Labs Hydrogen-L Bolt Action Rifle Muzzle Sound Pressure Signature, Short Time Window
Figure 4a. Otter Creek Labs Hydrogen-L Bolt Action Rifle Muzzle Sound Impulse Signature
Figure 4b. Otter Creek Labs Hydrogen-L Bolt Action Rifle Muzzle Sound Impulse Signature, Short Time Window
The Hydrogen-L exhibits FRP measured at the muzzle that is slightly perceptible to bystanders, in accordance with PEW Science inner ear modeling. The FRP is highlighted in both the pressure regime (Figure 3) and impulse regime (Figure 4). Although the Hydrogen-L does not completely mask FRP to bystanders, it performs higher in this area than the PR30L and Diligent Defense Enticer-L.
The jetting onset from the Hydrogen-L is significantly delayed. Note the low amplitude jetting occurring at approximately 31.25 ms (Fig 3b). Latent jetting does not peak until after 33 ms, the rise time to peak maximum positive phase impulse is long, and the initial slope is shallow (Fig 4a). Consistent with these measured pressure and impulse waveform features, the computed PEW Science Omega Metric is relatively high, placing the silencer in Omega Zone 7. Relative Suppression Rating and flow restriction (back pressure) data is presented in Section 6.81 of this review.
PEW Science Research Note 1: The Hydrogen-L, like the CGS Hyperion, Dead Air Nomad-L, and Thunder Beast ULTRA 9, produces impulse accumulation rates that are relatively consistent. Notably, the Hydrogen-L produces a muzzle impulse signature that is more consistent than the Otter Creek Labs PR30L. The shape and rate of the impulse accumulation measured at the muzzle (Figure 4a) shares characteristics with both the Nomad-L (significantly delayed onset of peak) and the ULTRA 9 (FRP post-peak consistency with subsequent shots).
PEW Science Research Note 2: Comparing the behavior of the six silencers with the highest supersonic suppression performance (Hydrogen-L, Enticer L, Hyperion, Nomad-L, PR30L, and ULTRA 9) highlights the thresholds of performance that can be achieved with each technology. Each of these silencers possesses similar attributes with key differences. The highest performing silencers of the group possess different implementations of outer coaxial flow paths. The Hydrogen-L bridges the gap between more conventional silencers like the ULTRA 9, and the aforementioned next-generation silencers like the Enticer-L.
As stated in SSS.6.67.1.1, it is postulated that the most efficient implementations of the aforementioned features typically reside in the highest pressure zones of the silencers’ internal geometries. PEW Science test data, to date, supports this hypothesis. However, it is important to note that the holistic sound signature suppression performance of these silencers is a function of many variables.
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.
6.81.2 Relative Suppression Rating and Back Pressure Comparisons (.30 Rifle Silencers)
The Hydrogen-L suppressor is intended to offer extreme sound signature suppression in a lightweight envelope, without significant regard to back pressure. PEW Science has developed an empirical relation to quantify the back pressure (flow restriction) of silencers. Figure 7 and Figure 8 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 end cap. 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 8).
Figure 7. 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 8. 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 in 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 2. PEW Science Back Pressure Metric Omega Zones And Suppressed Weapon System Functional Descriptions
The Hydrogen-L possesses sound suppression performance on this platform, on average, that is similar to class-leading silencers such as the Dead Air Nomad-L (Review 6.55), the CGS Hyperion (Review 6.27), and the Diligent Defense Enticer-L (Review 6.67). These full-length rifle silencers are classified as next-generation; their performance significantly eclipses that of more traditionally designed silencers, having high performance of their respective generations (for example, the Thunder Beast Ultra 9). The Otter Creek Labs Hydrogen-L bridges the gap between conventional design and the next generation; this is demonstrated in its internal geometry and the measured performance is consistent with this conclusion.
PEW Science Research Note 3: For the Hydrogen-L Composite Suppression Rating to approach the 50 zone, in its design envelope, is a notable performance attribute. It is the only rifle silencer tested by PEW Science to reach this level of performance without the use of some type of significant high pressure stagnation relief to manage gas dynamics. PEW Science acknowledges that this performance factor may be of no practical consequence to the end-user. However, of certain relevance are the limits of performance for conventional design. PEW Science postulates that the Hydrogen-L is approaching those limits on this host weapon.
PEW Science Research Note 4: The Otter Creek Labs Hydrogen-L is in Omega Zone 7 (Figure 8), which indicates that it exhibits significant flow restriction. As previously noted in the PEW Science testing and analysis of the Dead Air Nomad-L, adding baffles increases suppression performance, but the flow restriction (back pressure) increases accordingly. 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.
6.81.3 Review Summary: Otter Creek Labs Hydrogen-L on a Savage Model 10 .308 with 20-in Barrel
When paired with the Savage M10 20” .308 and fired with Federal XM80, the Otter Creek Labs Hydrogen-L, mounted with direct thread, achieved a Suppression Rating™ of 49.8 in PEW Science testing.
PEW Science Subjective Opinion:
The Otter Creek Labs Hydrogen-L is a full-size and lightweight 30 caliber rifle silencer that exhibits very high sound signature suppression performance. The Hydrogen-L is constructed of titanium and has a user-adaptable mounting system. At 13.8 ounces with the direct thread mount, the Hydrogen-L is one of the lightest full size high performance rifle silencers on the current market.
The Hydrogen-L uses a modified stepped cone baffle design in a tubeless welded construction, and does not use porting to an outer annulus. As the silencer is tubeless, this relatively simple geometry allows the Hydrogen-L to exhibit significant weight savings while maintaining adequate strength for magnum rifle cartridges. Despite the simple baffle design, the sound suppression performance of the Hydrogen-L is significant. The high performance of the silencer is due to a combination of the baffle design, their number, and its length. Nearing the Composite Suppression Rating 50 Zone on this host weapon, the Hydrogen-L exhibits performance close to that of more complex designs such as the Diligent Defense Enticer-L, Dead Air Nomad-L, and CGS Hyperion, all of which utilize at least some venting to outer annular space. The Hydrogen-L bridges the gap between next-generation silencers and conventional performance in the design envelope. It should be noted that the diameter of the silencer is 1.625 inches; the same diameter as the Enticer-L.
The rear mount threading of the Hydrogen-L is 1.375”-24tpi; relatively common in many modern rifle silencers. As a result of this common modular interface, a plethora of mounting systems may be used. The performance of the Hydrogen-L 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.
In this review, the Hydrogen-L 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.
