SSS.6.31 - SilencerCo Harvester 300 and the Savage Model 10 PC .308
/SilencerCo Harvester 300 on a Savage Model 10 .308 with 20-in Barrel
The Harvester 300 is designed and manufactured by SilencerCo. It is a 30 caliber centerfire rifle silencer, intended to suppress most cartridges with projectiles appropriately sized to travel through the bore, including 300 Winchester Magnum. It has a 1.375-inch diameter and is 8.84 inches in length. The silencer may be used with a direct-thread mount or with modular mount systems that interface with the SilencerCo Alpha thread interface. The Harvester 300 baffle stack is welded stainless steel, while the outer tube is aluminum. The silencer weighs 11.7 ounces with the direct thread adapter, as tested. The silencer has an externally mounted anchor brake attached at its end cap that is not user serviceable or removable. The Harvester 300 can be obtained from Silencer Shop.
This review contains single-test results using the Harvester 300 direct-thread mounted on the Savage Model 10 Precision Carbine rifle, chambered in .308WIN with a 20-inch barrel. Federal XM80C 149gr ammunition was used in the test.
The Harvester 300 was released by SilencerCo prior to the Omega 300. These silencers have key design differences in materials, baffle geometry, diameter, end-cap characteristics, and other geometric differences which result in different sound signature performance and back pressure traits. PEW Science evaluated the Omega 300 previously on the same supersonic .308WIN test host in Sound Signature Review 6.10.
Section 6.31.1 contains the results of the Harvester 300 test.
Section 6.31.2 contains relative back pressure and Suppression Rating comparisons with selected .30 rifle silencers.
Section 6.31.3 contains pertinent comparisons of the Harvester 300 and Omega 300 with high fidelity PEW-SOFT test data to illustrate the influence of key silencer component design differences, including the use of so-called “anchor brakes.”
Section 6.31.4 contains the review summary and subjective PEW Science opinions.
Summary: When paired with the Savage M10 20” .308 and fired with Federal XM80C, the SilencerCo Harvester 300 with direct-thread adapter and its attached anchor brake achieved a Suppression Rating™ of 34.5 in PEW Science testing.
Relative Suppression Rating Performance is Summarized in SSS.7 - PEW Science Rankings
6.31.1 SilencerCo Harvester 300 Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the Harvester 300 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. SilencerCo Harvester 300 Sound Metric Summary
6.31.1.1 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 1.5 millisecond long portion of the first round sound pressure signature of the Harvester 300 as measured 1.0 m left of the muzzle. There are three significant waveform features labeled:
Firing system manipulation results in a peak amplitude of approximately 107.3 dB.
The endcap exit event results in an initial overpressure peak magnitude of 140.0 dB.
Secondary jetting reaches a peak of 145.0 dB.
This is the typical sequence observed when firing supersonic .308WIN ammunition from a bolt-action rifle with an attached silencer that exhibits significant flow restriction (back pressure); however, internal silencer design can significantly influence the measured timing and pressure amplitudes. Preliminary back pressure comparisons are shown in Section 6.31.2 of this review.
Fig 1. SilencerCo Harvester 300 First Round Bolt Action Rifle Muzzle Sound Pressure Signature, 24-OCT-2020
For reference, the reader is also encouraged to review the performance data of the SilencerCo Omega 300 in Sound Signature Review 6.10. The Harvester 300 early-time signature differs from that of the Omega 300 in that the secondary jetting occurs more quickly and with higher amplitude. This is due to the different baffle spacing inside the Harvester, as well as the larger bore aperture when compared to that of the Omega. The two silencers also possess different diameters, and the Harvester has a permanent anchor brake. These additional differences further change the Harvester’s performance parameters, as discussed in Section 6.31.3.
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 coupled bullet end-cap exit and jet event, between all 5 shots during the test. Note the consistency in both amplitude and wave shape which are captured accurately due to the 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 0.3 milliseconds (300 microseconds) and the total timescale in Figure 2b is only 0.09 milliseconds (90 microseconds). PEW-SOFT provides a sampling point every microsecond and the individual data points are shown in Figure 2b to illustrate this.
Fig 2a. SilencerCo Harvester 300 Bolt Action Rifle Muzzle Sound Pressure Early-Time Peaks, 24-OCT-2020
Fig 2b. SilencerCo Harvester 300 Bolt Action Rifle Muzzle Sound Pressure Shot 1 Peak, 24-OCT-2020
The primary sound signature pressure histories for all 5 shots with the Harvester 300 are shown in Figure 3a. The sound signatures of all shots 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 4.
Fig 3a. SilencerCo Harvester 300 Bolt Action Rifle Muzzle Sound Pressure Signature, 24-OCT-2020
Fig 3b. SilencerCo Harvester 300 Bolt Action Rifle Muzzle Sound Pressure Signature, Short Time Window, 24-OCT-2020
Figure 4a. SilencerCo Harvester 300 Bolt Action Rifle Muzzle Sound Impulse Signature, 24-OCT-2020
Figure 4b. SilencerCo Harvester 300 Bolt Action Rifle Muzzle Sound Impulse Signature, Short Time Window, 24-OCT-2020
The SilencerCo Harvester 300 does exhibit perceptible first round pop (FRP). There is FRP in the pressure regime, and it is further evident upon examination of the impulse waveforms in Figure 4 in both rise impulse rise time and slope. However, the FRP is not significant. PEW Science inner ear modeling indicates FRP may only be perceptible to bystanders and not necessarily to the shooter with the Harvester 300 on this host weapon platform.
PEW Science Note 1: There is a wave shape anomaly present in impulse space, in late time. After decay from primary positive phase impulse, the sound signature measured at the muzzle stays in the positive phase for up to 5 ms longer than noted in the test of the Omega 300. Although the silencers are of significantly different design, as noted above, this type of behavior is highly atypical and it is postulated this occurs due to secondary and tertiary reflections induced by the anchor brake. By influencing the positive to negative phase oscillations in sound pressure venting out of the end-cap, the anchor brake is postulated to create (or force) a longer positive phase impulse duration. This actually results in a less severe sound signature measured adjacent to the muzzle than with the Omega 300 which possesses a tighter bore and larger diameter, but was tested without its removable anchor brake. The anchor brake of the Harvester 300 is not removable. Detailed comparisons are presented in Section 6.31.3 of this review. The conclusions at the shooter’s ear, however, are the opposite; the influence of the anchor brake results in adverse sound signature at the ear for the shooter. This data is examined in the PEW Science member version of this review.
PEW Science Note 2: Another notable observation from the measured data is the sharper nature of the maximum positive phase impulse peaks of the Harvester 300 waveforms measured at the muzzle when compared to those measured with the Omega 300. The rise-time to peak impulse is faster, as well as the decay time; the difference is not extreme, but it is measurable, and the back pressure metric reflects this difference. Detailed backpressure comparisons of these silencers are presented in Section 6.31.2 of this review. Prior to this review publication, PEW Science received concurrence from SilencerCo R&D with regard to the efficacy of the PEW Science relative back pressure metric analysis for the Harvester 300 and Omega 300 silencers.
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.
6.31.1.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 5-shot test of the Harvester 300 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 5. 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. SilencerCo Harvester 300 Bolt Action Rifle Ear Sound Pressure Signature, 24-OCT-2020
Figure 5b. SilencerCo Harvester 300 Bolt Action Rifle Ear Sound Pressure Signature, Short Time Window, 24-OCT-2020
Figure 6a. SilencerCo Harvester 300 Bolt Action Rifle Ear Sound Impulse Signature, 24-OCT-2020
Figure 6b. SilencerCo Harvester 300 Bolt Action Rifle Ear Sound Impulse Signature, Short Time Window, 24-OCT-2020
When examining the impulse waveforms measured at the shooter’s ear with the Harvester 300 (Figure 6), it exhibits extremely high peaks when compared to that of the Omega 300 in Sound Signature Review 6.10. This is postulated to result from the anchor brake. Both the peak sound pressure and impulse at the shooter’s ear are higher with the Harvester, which significantly influences the at-ear Suppression Rating. Although FRP can be identified in the data in the latent impulse histories, the magnitude is low and PEW Science inner-ear modeling confirms FRP is not significant to the shooter. However, all of the shots are louder due to the anchor brake, so FRP is less of a significant performance characteristic for the shooter to note, than is overall loudness.
The overall sound signature measured at the shooter’s ear actually possesses higher sound pressure than that measured at the muzzle on this host platform. This is the first time this has been observed with a centerfire rifle silencer on this host platform by PEW Science. Again, this is postulated to result from the anchor brake. Although the peak pressure is higher, the overall signature is less severe than the signature at the muzzle; therefore, the at-ear Suppression Rating is still higher than the muzzle Suppression Rating.
6.31.2 Relative Back Pressure and Suppression Rating Comparison (.30 Rifle Silencers)
PEW Science Research Note: As of February 2021, back pressure characterization has undergone refinement and Rev.2 of the Back Pressure Metric has been developed. Research is ongoing. Please see back pressure research updates starting with Sound Signature Review 6.36.
The Harvester 300 suppressor is intended to be light weight and used for hunting, precision rifle shooting, and other bolt gun-centric roles with anchor brake recoil control and good sound suppression performance, without regard for back pressure. PEW Science is currently conducting silencer back pressure research. Figure 7 shows preliminary relative 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 time to reach peak gas momentum transfer potential, as measured 1.0 m left of the weapon muzzle, is the objective quantity used to generate the back pressure data summary.
The waveform characteristics of unsuppressed shots with the same ammunition used in the respective tests are used in the calculations and the unsuppressed relative back pressure and Suppression Rating quantities are shown.
The first shot from each silencer test is omitted from the back pressure computations due to internal gas environment characteristics within the silencer (FRP) that influence peak impulse amplitude, wave-shape, and timing. All unsuppressed shots are included.
Back Pressure Data is normalized to the silencer with the highest back pressure shown, which is the Thunder Beast ULTRA 9 from Sound Signature Review 6.24.
Figure 7. Back Pressure And Suppression Rating Comparisons Of .308 Rifle Silencers Using PEW-SOFT Data
From the above data, it can be concluded that the SilencerCo Harvester 300 suppressor may produce slightly lower back pressure than the SilencerCo Omega 300. The reasons for this slightly reduced back pressure are postulated to be due to the slightly larger bore, as well as the smaller diameter which influences flow velocity. The postulated 3% lower back pressure of the Harvester when compared to the Omega is not significant, but it is measurable.
It is also important to note that the back pressure potential of silencers, in general, may not be significant in practical use. For example, the Harvester 300 is intended for use on bolt-action rifles in which back pressure should not be of practical concern with proper silencer mount sealing. For an example of severe performance differential when mount sealing is compromised due to mount design, see the PEW Science data with the Surefire WARCOMP mount and SOCOM762-RC2 in Sound Signature Review 6.26.
It is important to note that back pressure is not the same phenomenon as blow back. Back pressure may cause blow back on a host weapon, or it may not influence host weapon operation when compared to the unsuppressed state; the influence of back pressure characteristics on a silencer’s performance on semi-automatic and automatic hosts may depend on the respective metric magnitudes; this is the subject of future PEW Science research. For example, it is postulated that there is a threshold back pressure metric below which adequate semi-automatic weapon function on typical 5.56x45mm host weapons may be achieved. Whether that threshold is 0.73 in Figure 7 (Helios with its solid end-cap) or 0.54 (Harvester 300), for example, will depend on the particular host weapon configuration. Recent PEW Science research at the time of this review publication indicates that a back pressure metric threshold is probable for gas operated 5.56x45mm small arms. Current research indicates that host weapon component dynamics (AR15 platform bolt carrier, buffer mass, and gas port size) can significantly influence suppressed weapon system performance. Further research is ongoing.
For example, an 11.5-inch AR15 chambered in 5.56x45mm with a mid-length gas system and adequate reciprocating mass (an H3 buffer weight, for example) may be able to be suppressed with any silencer shown in Figure 7 without undue gas blow back noted by the shooter. This type of suppressed small arm weapon system is an example of a gas insensitive host. Conversely, a 14.5-inch AR15 in the same chambering with a carbine-length gas system, relatively large gas port, and standard weight carbine buffer, may produce severe gas blow back noted by the shooter, even with a silencer such as the Surefire SOCOM762 RC2, which is shown in Figure 7 to have a normalized back pressure metric much lower than other full size silencers. This type of suppressed small arm weapon system is an example of a gas sensitive host. On the AR15 platform, silencer gas flow (back pressure) sensitivity is a function of dwell time, inertial resistance, and lock time. Other host weapon types have characteristics that result in more or less gas sensitivity in suppressed operation.
PEW Science note: The relative back pressure percentages described in this section are only valid when examining the data normalized to the ULTRA 9 in Figure 7. PEW Science back pressure research is ongoing. Membership contributions to PEW Science help fund such research.
The SilencerCo Harvester 300 is slightly quieter than the Omega 300 to observers, but it is louder than the Omega 300 at the shooter’s ear, due to the anchor brake. Its back pressure is postulated to be slightly lower than that of the Omega 300.
6.31.3 Harvester 300 and Omega 300 Comparisons
The SilencerCo Omega 300 without an anchor brake was previously evaluated by PEW Science in Sound Signature Review 6.10. Below, comparisons of the first shot from that test are shown with the first shot of the Harvester 300. The Harvester 300 includes an anchor brake that is not user-serviceable. While the anchor brake is not the only variable in these tests (the silencers have different geometries and baffle characteristics), its gross influence is still notable, especially in the signature measured at the shooter’s ear.
Figure 8 shows comparisons of sound pressure measured 1.0 m left of the silencer end cap (left) and impulse (right).
Figure 8a. SilencerCo Harvester 300 and Omega 300 Bolt Action Rifle Muzzle Sound Pressure Signature Comparison (FRP)
Figure 8b. SilencerCo Harvester 300 and Omega 300 Bolt Action Rifle Muzzle Sound Impulse Signature Comparison (FRP)
As previously described in Section 6.31.1.1, the Harvester 300 vents gas more quickly due to larger bore aperture and the anchor brake prolongs the positive phase when compared to the Omega 300. The Omega 300 has higher pressure amplitude than the Harvester 300, but lower impulse. Nonetheless, the Omega 300 is louder at the muzzle.
Figure 9, below, compares the waveforms measured near the shooter’s ear. The effects of anchor brake use on the sound signature observed by the shooter are significant.
Figure 9a. SilencerCo Harvester 300 and Omega 300 Bolt Action Rifle Ear Sound Pressure Signature Comparison (FRP)
Figure 9b. SilencerCo Harvester 300 and Omega 300 Bolt Action Rifle Ear Sound Impulse Signature Comparison (FRP)
The difference at the ear is drastic. In both pressure and impulse space, the sound signature of the Harvester 300 is much more severe than that of the Omega 300. At the muzzle, the prolonged positive phase impulse was observed to lessen the severity of the signature. To the shooter, however, the anchor brake of the Harvester seems to create severe reflections rearward from the muzzle that subject the shooter to signature components magnified to levels over four times more intense than measured with the Omega 300. PEW Science does not recommend the use of an anchor brake for users concerned with at-ear sound signature suppression performance.
6.31.4 Review Summary: SilencerCo Harvester 300 on a Savage Model 10 .308 with 20-in Barrel
When paired with the Savage M10 20” .308 and fired with Federal XM80C, the SilencerCo Harvester 300 with direct-thread adapter and its attached anchor brake achieved a Suppression Rating™ of 34.5 in PEW Science testing.
PEW Science Subjective Opinion:
The SilencerCo Harvester 300 is a full-size 30 caliber rifle silencer that possesses light weight, good sound signature suppression performance for its design envelope, and built-in recoil reduction with its attached anchor brake. The silencer is smaller diameter than many rifle silencers; in fact, it is similar in diameter to many 9mm pistol silencers.
The Harvester 300 uses baffles similar to those in the Omega 300; albeit with a greater spacing and with smaller overall diameter. The bore aperture is slightly larger than that of the Omega. These factors influence its sound performance, but PEW Science postulates that the most significant influence on its sound performance when compared to the Omega 300 is caused by the anchor brake.
The anchor brake functions to reduce felt recoil or muzzle rise to shooters by routing expanding propellant gasses out of the silencer end cap into advantageous directions of jetting thrust. While this phenomenon is measurable and anecdotally reported to enhance performance parameters on precision rifles, for example, the adverse sound suppression performance to the shooter may be significant. As PEW Science data and The Suppression Rating shows, perceived loudness and the severity of sound signatures to the human inner ear are functions of many waveform characteristics; the anchor brake results in less than optimal shaping of such characteristics. PEW Science does not recommend the use of anchor brakes for users concerned with at-ear sound signatures on bolt action rifles. While benefits ancillary to sound signature may be realized, sound suppression performance can be easily improved by the removal of such apparatus. The anchor brake on the Harvester 300 is not intended to be user-serviceable.
The Harvester is relatively long, but has a small diameter and is light. Similar to the Omega 300, it offers respectable sound suppression performance for its design envelope; this is no doubt due to the exceptional performance of its curved-cone baffles which share some characteristics with the Omega baffle design (patented by Joe Gaddini of SWR and named by the late William Ellison).
In this review, the Harvester 300 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.
