SSS.6.48 - Otter Creek Labs PR30L and the Savage Model 10 PC .308
/Otter Creek Labs PR30L on a Savage Model 10 .308 with 20-in Barrel
The PR30L is designed and manufactured by Otter Creek Labs. It is a 30 caliber centerfire 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 the silencer body is 8.36 inches in length. The total length with the included direct thread adapter is 8.77 inches. The user may choose to use third-party adapters compatible with the 1.375”-24tpi system. The silencer tube is Grade 9 titanium, while the primary baffle stack is constructed from Grade 5 titanium. The blast baffle is constructed from 17-4 heat treated stainless steel. The silencer body weighs 14.6 ounces and the system weighs 16.4 ounces with the direct thread mount, as tested. The PR30L can be obtained from Stockpile Defense.
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-016-001-21. Therefore, data pertaining to the PR30L 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 PR30L 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 6.48.1 contains the PR30L test results and analysis.
- Section 6.48.2 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. Further information about the Ω metric and Omega Zones can be obtained in PEW Science Research Supplement 6.40 (Public Article).
- Section 6.48.3 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 PR30L mounted with the direct thread adapter, achieved a Suppression Rating™ of 46.4 in PEW Science testing.
Test data for the compact version of this silencer, the Otter Creek Labs PR30S, can be found in Sound Signature Review 6.49.
Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings
6.48.1 Otter Creek Labs PR30L Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the PR30L 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. Otter Creek Labs PR30L Sound Metric Summary
6.48.1.1 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 3 millisecond long portion of the first round sound pressure signature of the PR30L as measured 1.0 m left of the muzzle. There are four significant waveform features labeled:
Internal combustion within the system reaches a peak magnitude of 124.6 dB.
The endcap exit event results in an initial overpressure peak magnitude of 141.0 dB.
The first major jet builds to an amplitude of 139.2 dB.
Subsequent peaks occur over 141.1 dB with peak FRP measured to reached a maximum overpressure amplitude of 141.8 dB later in time.
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 6.48.2 of this review, with the PEW Science Back Pressure Metric, Ω [Pa-1].
Fig 1. Otter Creek Labs PR30L First Round Bolt Action Rifle Muzzle Sound Pressure Signature, 25-JUL-2021
The Otter Creek Labs PR30L exhibits sound signature waveform characteristics that share some similarities with the Thunder Beast ULTRA 9 (Review 6.24) and the CGS Hyperion (Review 6.27). The most prominent features of the signature highlighting the similarities are the significantly decoupled bullet exit event from the main combustion jetting, followed by subsequent jetting that slightly eclipses the magnitude of the exit event. Although the subsequent jetting does not stay below the peak amplitude of the bullet exit event, the latent magnitudes remain below a threshold indicative of high flow restriction, lowering the signature to levels only found in silencers with relatively high sound suppression performance. The PR30L is quieter than the Thunder Beast ULTRA 9.
The PR30L uses a modified and broadened stepped-cone adaptation of the so-called Omega baffle; combustion gasses are able to avoid high pressure stagnation by flowing through relief ports into voids between the outer baffle walls and the silencer tube. This basic premise of silencer baffle design and configuration results in significantly more gas retention than geometries lacking adequate flow paths for gasses after initial volume pressure stagnation. PEW Science postulates that this technology prevents excessive shedding of flow across defined boundary layers in the primary jet. The sound suppression performance of the PR30L is somewhat typical for this type of design, but the performance in its size envelope is notable. Silencers that share some similar design features include the Dead Air Nomad series (Review 6.43) and the aforementioned CGS Hyperion.
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 endcap exit event between all 5 shots during the test. The endcap exit signature consistency in both amplitude and wave shape, from shot to shot, is 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 0.44 milliseconds (440 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. Otter Creek Labs PR30L Bolt Action Rifle Muzzle Sound Pressure Early-Time Peaks, 25-JUL-2021
Fig 2b. Otter Creek Labs PR30L Bolt Action Rifle Muzzle Sound Pressure Shot 1 Peak, 25-JUL-2021
The primary sound signature pressure histories for all 5 shots with the PR30L 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.
Fig 3a. Otter Creek Labs PR30L Bolt Action Rifle Muzzle Sound Pressure Signature, 25-JUL-2021
Fig 3b. Otter Creek Labs PR30L Bolt Action Rifle Muzzle Sound Pressure Signature, Short Time Window, 25-JUL-2021
Figure 4a. Otter Creek Labs PR30L Bolt Action Rifle Muzzle Sound Impulse Signature, 25-JUL-2021
Figure 4b. Otter Creek Labs PR30L Bolt Action Rifle Muzzle Sound Impulse Signature, Short Time Window,25-JUL-2021
The PR30L does exhibit perceptible first round pop (FRP) at the muzzle on this platform, though it is not severe. The FRP phenomenon is predominantly observed in the impulse regime, as shown in Figure 4, in both rise time and amplitude. It is very interesting to note the performance of the PR30L relative to that of the Thunder Beast ULTRA 9; the comparison of which illustrates two silencers with similar sound suppression performance overall, but with two different design approaches producing significantly different sound signatures in impulse space. The ULTRA 9 exhibits a steeper initial impulse rise time with a rate shift prior to peak, whereas the PR30L maintains a relatively linear impulse slope and keeps it below a lower post-FRP threshold amplitude.
PEW Science Research Note: While the gross signatures of the PR30L, from shot to shot, are more consistent to the human ear than with the ULTRA 9, the ULTRA 9 exhibits more consistent flow characteristics measured in impulse space. This waveform consistency differential may be the result of excessive annular porting in the PR30L; a characteristic that may be of no practical consequence other than increased sound suppression. The sound signature suppression performance of the PR30L is notable.
The PR30L is quieter (and shorter) than the Rugged Surge (Review 6.22) and Thunder Beast ULTRA 9 (Review 6.24). It does not reach the sound suppression performance of the CGS Hyperion (Review 6.27). The overall, muzzle, and ear Suppression Ratings for silencers tested by PEW Science, to date, can be compared directly using the tool in Section 7 of the Silencer Sound Standard - PEW Science Rankings. Section 6.48.2 of this review presents a comparison of Suppression Rating and back pressure for silencers with a flow restriction above a certain threshold (Omega Zone 5). Comprehensive silencer back pressure comparisons for .30 rifle silencers are available in PEW Science Public Research Supplement 6.40.
The Otter Creek Labs PR30L exhibits lower flow restriction (back pressure) than the CGS Hyperion, but higher back pressure than the Thunder Beast ULTRA 9.
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.
6.48.1.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 5-shot test of the PR30L suppressor 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 5. 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 6. Again, full and short timescales are shown.
Figure 5a. Otter Creek Labs PR30L Bolt Action Rifle Ear Sound Pressure Signature, 25-JUL-2021
Figure 5b. Otter Creek Labs PR30L Bolt Action Rifle Ear Sound Pressure Signature, Short Time Window, 25-JUL-2021
Figure 6a. Otter Creek Labs PR30L Bolt Action Rifle Ear Sound Impulse Signature, 25-JUL-2021
Figure 6b. Otter Creek Labs PR30L Bolt Action Rifle Ear Sound Impulse Signature, Short Time Window, 25-JUL-2021
When examining the impulse waveforms measured at the shooter’s ear with the PR30L (Figure 6), it exhibits less significant FRP in the impulse regime than at the muzzle. The PR30L exhibits no FRP in the pressure regime at the shooter’s ear. In PEW Science inner-ear modeling, the FRP may be noticeable to the shooter on this platform, but it is not significant. The reader should note that the relatively erratic nature of the late time impulse variation is somewhat due to the small amplitude scale used in the plots. This late time variation in impulse space is relatively common at extremely low signature amplitude.
In a very similar fashion to the CGS Hyperion and Thunder Beast ULTRA 9, the PR30L reduces the magnitude of latent impulse peaks at the shooter’s head position to less than that from the combustion within the weapon system. This is one indication of significantly high sound suppression performance.
6.48.2 Relative Suppression Rating and Back Pressure Comparisons (.30 Rifle Silencers)
The Otter Creek Labs PR30L suppressor is intended to maximize sound signature suppression for precision rifle use, without concern for back pressure. PEW Science has developed an empirical relation to quantify the back pressure (flow restriction) of silencers. Figure 7 shows 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 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 2, 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.
Figure 7. Omega Back Pressure Metric And Suppression Rating 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 2. PEW Science Back Pressure Metric Omega Zones And Suppressed Weapon System Functional Descriptions
The PR30L is quieter than the Rugged Surge (Review 6.22), Thunder Beast ULTRA 9 (Review 6.24), and the Q Thunder Chicken (Review 6.20), and exhibits higher back pressure than all of those silencers. The difference in back pressure between the PR30L and the Thunder Chicken may be significant, for example. This performance attribute may be of no consequence for precision rifle use.
The PR30L is one of the few silencers to surpass an at-ear Suppression Rating of 45.0 on the 20-in barrel bolt action .308 test host in PEW Science testing. Silencers with this level of sound suppression on this test platform are atypical.
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.
6.48.3 Review Summary: Otter Creek Labs PR30L 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 PR30L mounted with the direct thread adapter, achieved a Suppression Rating™ of 46.4 in PEW Science testing.
PEW Science Subjective Opinion:
The Otter Creek Labs PR30L is full-size but relatively light weight .30 precision rifle silencer that exhibits notable sound suppression performance. The PR30L allows for the use of third-party mount adapters with the standard 1.375”-24tpi system. There is also a shorter and lighter version of the silencer available, designated the PR30S. The silencers are of similar external and internal construction, and the PR30S exhibits less sound suppression due to the smaller size.
The PR30L uses a modified and broadened stepped-cone adaptation of the so-called Omega baffle; combustion gasses are able to avoid high pressure stagnation by flowing through relief ports into voids between the outer baffle walls and the silencer tube. This basic premise of silencer baffle design and configuration results in significantly more gas retention than geometries lacking adequate flow paths for gasses after initial volume pressure stagnation. PEW Science postulates that this technology prevents excessive shedding of flow across defined boundary layers in the primary jet. The sound suppression performance of the PR30L is somewhat typical for this type of design, but the performance in its size envelope is notable. Silencers that share some similar design features include the Dead Air Nomad series and the CGS Hyperion. Note that the PR30L has a 1.625-in diameter and the primary module is less than 8.5-in long.
The back pressure generation of the PR30L is relatively high, but for its intended use with precision bolt-action rifles, this is not of significant consequence. Users interested in using the PR30L with semi-automatic and automatic host weapons are encouraged to consider the PEW Science Omega metric and possible adjustments to host weapons as required. The silencer is not user serviceable. PEW Science recommends that users contact the manufacturer for information on silencer maintenance, firing schedule, and barrel length restriction information.
In this review, the PR30L 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.
