SSS.6.158 - Gemtech Neutron 7.62 and the Savage Model 10 PC .308
/Gemtech Neutron 7.62 on a Savage Model 10 .308 with 20-in Barrel
The Neutron 7.62 is manufactured by Gemtech. It is a 30 caliber centerfire rifle silencer, intended to suppress many cartridges with projectiles appropriately sized to travel through the bore, including 300 Winchester Magnum. It has a 1.625-inch diameter and is 6.6 inches in length, without a mount. The user may choose to install third-party adapters compatible with the 1.375”-24tpi system. The total length with the tested direct-thread mount is 7 inches. The silencer is tubeless; its baffles are manufactured from 17-4 heat treated stainless steel. As tested, the silencer weighs 14.9 ounces and the direct-thread mount weighs 1.9 ounces, for a total tested system weight of 16.8 ounces. The Neutron 7.62 can be obtained from Silencer Shop.
PEW Science is an independent private testing laboratory and also hosts the world’s only independent public 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-SW-065-001-24. Therefore, data pertaining to the Neutron 7.62 in this Sound Signature Review is published with the express written permission of Smith & Wesson Brands, Inc.
This review contains single test results using the Neutron 7.62 with a 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 6.158.1 contains the Neutron 7.62 test results and analysis.
- Section 6.158.2 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 below. 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 6.158.3 contains the review summary and PEW Science laboratory staff technical opinions.
Summary: When paired with the Savage M10 20” .308 and fired with Federal XM80, the Gemtech Neutron 7.62 with a direct thread mount achieved a Suppression Rating™ of 38.4 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
6.158.1 Gemtech Neutron 7.62 Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the Neutron 7.62 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. Gemtech Neutron 7.62 Sound Metric Summary
6.158.1.1 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.
The primary sound signature pressure histories for all 5 shots with the Neutron 7.62 are shown in Figure 1a. The sound signatures of Shot 1, Shot 2, and Shot 3 are shown in Figure 1b, in early time. The real sound impulse (momentum transfer potential) histories from the same 5-shot test are shown in Figure 2a. In Figure 2b, a shorter timescale is shown comparing the impulse of the first three shots.
Fig 1a. Gemtech Neutron 7.62 Bolt Action Rifle Muzzle Sound Pressure Signature
Fig 1b. Gemtech Neutron 7.62 Bolt Action Rifle Muzzle Sound Pressure Signature, Short Time Window
Figure 2a. Gemtech Neutron 7.62 Bolt Action Rifle Muzzle Sound Impulse Signature
Figure 2b. Gemtech Neutron 7.62 Bolt Action Rifle Muzzle Sound Impulse Signature, Short Time Window
Figure 1b shows a 1.2 millisecond long portion of the sound pressure signatures of the first three rounds fired from the Gemtech Neutron 7.62, as measured 1.0 m left of the muzzle. There are several significant waveform features labeled:
Internal combustion within the silencer is relatively consistent and reaches a peak of 118.2 dB.
The end cap exit event, consisting of bullet shock and the initial jet, results in a peak overpressure magnitude of 144.2 dB.
Primary first-round-pop (FRP) jetting occurs early, diverging from normalized flow.
Peak pressure amplitudes occur during latent jetting, after persistent jet pulses.
This is a somewhat typical sequence observed when firing supersonic .308WIN ammunition from a bolt-action rifle with an attached silencer that exhibits relatively low to 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 6.158.3 of this review, with the PEW Science Back Pressure Metric, Ω [Pa-1]. Note that weapon system influence is a function of both Ω and early-time wave propagation factors which may be measured inside the system, in close proximity to the muzzle orifice. These factors include the PEW Science alpha parameter; a subject of internal research.
PEW Science Research Note 1: The Gemtech Neutron 7.62 possesses vent structures in its baffle array and end cap that are shown in the above test data to increase the rate of gas momentum transfer potential to atmosphere. The venting in the throat of the blast baffle, along with venting into each of the baffle annular cavities, reduces pressure stagnation. The gas momentum transfer through the Neutron 7.62 is somewhat unique in that the measured blast impulse peaks and decays relatively rapidly, up to peak accumulation. This oscillatory phenomenon is shown in Figure 2b, between approximately 30 and 30.5 ms. This type of momentum transfer oscillation, with a consistent upward trend, is postulated to result from a combination of the alternating annular vented cavities and the multi-stage vented end-cap of the silencer, which is designed for flash reduction. Consequences of this behavior to sound signature severity are discussed in Research Note 3.
PEW Science Research Note 2: It is interesting to note that the baffle geometry in the Neutron 7.62 is somewhat similar to that in the Dead Air Nomad (6.43) and Dead Air Nomad-Ti (6.44), with the two primary differences being the throat angle and porting geometry, which change the angle of incidence and stagnation pressure thresholds, respectively. The Gemtech Neutron 7.62 also has one less baffle than the Nomad series. Along with the ported blast baffle throat, these differences culminate in the Neutron 7.62 having a higher distal flow rate than the Nomad series; a design intention from Gemtech. This results in a measured blast impulse accumulation rate from the silencer that places it in Omega Zone 4 (ref. 6.40). It is important to note that neither the Gemtech Neutron 7.62, nor the Dead Air Nomad series, should be considered “low back pressure” rifle silencers, relative to higher flow rate models on the market (i.e. HUXWRX, PTR, CAT, Surefire RC3, SilencerCo Velos, etc).
PEW Science Research Note 3: The FRP from the Neutron 7.62 on this host weapon is significantly divergent in impulse space (Figure 2). However, PEW Science analysis indicates that bystanders immediately adjacent to the muzzle may not experience adverse hazards relative to subsequent shots. It is postulated that the severity of subsequent shots may be increased due to the oscillatory phenomenon described in Research Note 1, which then nullifies the benefits of lower amplitude accumulation later in the string. It should be noted that muzzle pressure sensor locations are in-line with the silencer’s end cap; silencers with some types of end cap venting arrays therefore present with lower muzzle Suppression Ratings due to pressure field shape and sensor location. As this is a bolt-action rifle test, the suppressed pressure field shape is also indicated from the shooter’s ear measurements and expressed in the calculated shooter’s ear Suppression Rating; the lack of weapon reciprocation and ancillary blast pressure sources allow for this variable isolation. When examining the pressure field near the shooter, there is shown to be a significant gradient. The shooter’s ear hazard level is significantly less severe than to personnel adjacent to the silencer on this weapon system. This is further discussed in the full Member Version of this report.
PEW Science Research Note 4: There is some post-peak inconsistency in blast impulse accumulation after FRP that may be a result of pressure stagnation relief varying during continuous fire as temperature increases. PEW Science analysis indicates that bystander risk does increase as the shot string continues, post-FRP. Nonetheless, the gross suppression performance of the Gemtech Neutron 7.62 is similar to that of the SilencerCo Omega 300 (6.10), which is longer. The Neutron 7.62 outperforms the first generation Dead Air Nomad-30 (6.43), despite the Nomad having a larger diameter. The Gemtech Neutron 7.62 also outperforms the Q Trash Panda (6.4), which is both longer and larger diameter than the Neutron 7.62. Silencers that outperform the Neutron 7.62 on this host weapon are typically larger or longer, though there are exceptions. The reader is encouraged to view the PEW Science Rankings Section of the Standard for comprehensive comparison.
Again, consistent with the above measured pressure and impulse waveform features, the computed PEW Science Omega Metric is relatively low to moderate, placing the silencer in Omega Zone 4. Relative Suppression Rating and flow restriction (back pressure) data is presented in Section 6.158.2 of this review.
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.
6.158.1.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 5-shot test of the Gemtech Neutron 7.62 acquired with PEW-SOFT at the shooter’s ear are shown below. Again, the waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science testing is 1.0 MS/s (1 MHz).
The primary sound signature pressure histories at the ear for all 5 shots are shown in Figure 3. The primary sound signature history is shown on the left. A zoomed-in timescale is displayed on the right, in the region of peak sound pressure for Shot 1, Shot 2, and Shot 3. The real sound impulse (momentum transfer potential) histories at the ear from the same 5-shot test are shown in Figure 4. Again, full and short timescales are shown.
Figure 3a. Gemtech Neutron 7.62 Bolt Action Rifle Ear Sound Pressure Signature
Figure 3b. Gemtech Neutron 7.62 Bolt Action Rifle Ear Sound Pressure Signature, Short Time Window
Figure 4a. Gemtech Neutron 7.62 Bolt Action Rifle Ear Sound Impulse Signature
Figure 4b. Gemtech Neutron 7.62 Bolt Action Rifle Ear Sound Impulse Signature, Short Time Window
As is the case with many silencers fired from bolt-action rifles, the reduction in the amount of overpressure sources allow for isolation of signature variables in the measurements at the shooter’s head. In the case of this bolt-action test with the Gemtech Neutron 7.62, many of the same features observed adjacent to the weapon muzzle are again observed in a different location of the sound field. At the operator’s head, the same type of gas momentum oscillation is noted (Figure 4b, 30.5 ms) along with the same inconsistency post-peak. However, this time, the oscillation is reduced in amplitude due to standoff. This causes a greater differential in signature severity between the first shot and subsequent shots, which in turn results in FRP being more severe to the shooter. This is in contrast to the muzzle severity being similar during FRP, as previously described in Research Note 3.
PEW Science Research Note 5: In general, the signatures at the shooter’s ear are lower amplitude than those measured adjacent to the muzzle. There are also some blast load propagation phenomena that differ not only in decay, but in shape. The distal flow rate of the Neutron 7.62 is higher than many silencers, which may contribute to further non-uniformity of the sound field. This is not necessarily a negative trait, as the severity of operator hazard with this system is more uniform, post-FRP, than it is to bystanders. The sound field created by the Neutron 7.62 to the shooter on this host weapon system is more consistent than the field to which bystanders may be subjected.
PEW Science Research Note 6: It is interesting to note that the same oscillatory behavior that occurred in pre-peak flow measured at the muzzle (Research Note 1) is observed post-peak at the shooter’s ear, and also in the FRP measurement. It is possible that the momentum decay from shooter standoff allows the phenomenon to be observed during FRP. More research is needed.
As typical, the overall sound signature measured at the shooter’s ear possesses significantly less amplitude in both the pressure and impulse regimes than the signature measured at the muzzle (refer to Table 1). Furthermore, the application of both pressure and impulse at the shooter’s ear is delayed when compared to the pressure and impulse at the weapon muzzle. The combination of varying amplitude and rise time to peak amplitude influences the response of the human ear.
It is extremely important to note that muzzle signature influences the signature to the weapon operator. This is a test on a bolt-action rifle. Similar jetting phenomenon measured at the muzzle propagates toward the shooter. The standoff of the endcap to the shooter, as well as angle of incidence of the pressure (blast) waves, result in exponential decay of hearing damage risk when compared to personnel adjacent to the muzzle.
6.158.2 Relative Suppression Rating and Back Pressure Comparisons (.30 Rifle Silencers)
The Gemtech Neutron 7.62 suppressor is intended to offer competitive sound signature suppression with somewhat lower flow restriction (back pressure) than similarly sized models. PEW Science has developed an empirical relation to quantify the back pressure (flow restriction) of silencers. Figure 5 and Figure 6 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 5 and Figure 6 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. Note that weapon system influence is also a function of early-time wave propagation factors which may be measured inside the system, in close proximity to the muzzle orifice. These factors include the PEW Science Alpha parameter; a subject of internal research.
The Back Pressure Metric relations are most easily viewed on a logarithmic scale (See Figure 6).
Figure 5. 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 6, 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 6. 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 3. PEW Science Back Pressure Metric Omega Zones And Suppressed Weapon System Functional Descriptions
As stated above, weapon system influence is a function of both Ω and early-time wave propagation factors which may be measured inside the system, in close proximity to the muzzle orifice. These factors include the so-called PEW Science Alpha parameter; a subject of internal research. The Gemtech Neutron 7.62 was tested with a direct thread mount which most likely does not significantly influence early time shock reflections near the muzzle, but more testing is needed to determine this influence. Mount geometry, chamber geometry, and the blast baffle shape all contribute to early-time flow restriction, in addition to late-time flow restriction characterized by Omega.
The gross suppression performance of the Gemtech Neutron 7.62 is similar to that of the SilencerCo Omega 300 (6.10), which is longer. The Neutron 7.62 outperforms the first generation Dead Air Nomad-30 (6.43), despite the Nomad having a larger diameter. The Gemtech Neutron 7.62 also outperforms the Q Trash Panda (6.4), which is both longer and larger diameter than the Neutron 7.62.
The Gemtech Neutron 7.62 outperforms the Otter Creek Labs Polonium-30 (6.142), while being slightly longer. The Neutron 7.62 is significantly quieter than the Dead Air Sandman-S (6.11), while being both shorter and lighter. The Neutron 7.62 is eclipsed in performance by silencers like the Dead Air Nomad-Ti (6.44), the larger FOR Systems Monarch 7.62 (6.155), and the Q Thunder Chicken (6.20). The reader is encouraged to view the PEW Science Rankings Section of the Standard for comprehensive comparison.
PEW Science urges the reader not to misconstrue a low Omega metric with the mirroring of unsuppressed weapon function, nor 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. Note that weapon system influence is also a function of early-time wave propagation factors which may be measured inside the system, in close proximity to the muzzle orifice.
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 PEW Science Suppression Rating computation considers all of these factors.
6.158.3 Review Summary: Gemtech Neutron 7.62 on a Savage Model 10 .308 with 20-in Barrel
When paired with the Savage M10 20” .308 and fired with Federal XM80, the Gemtech Neutron 7.62 mounted with a direct-thread mount achieved a Suppression Rating™ of 38.4 in PEW Science testing.
As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.
PEW Science Laboratory Staff Opinion:
The Gemtech Neutron 7.62 is a mid-size 7.62mm rifle silencer that possesses competitive sound signature suppression performance in a somewhat smaller and lighter envelope than some competing designs. The silencer is tubeless and possesses universal rear mount threading for adaptability to a wide variety of host weapon platforms, as well as a removable end cap that has purposely designed flash hiding features.
The user may choose to install third-party adapters compatible with the 1.375”-24tpi system. The Neutron may be obtained with Gemtech’s ETM quick-detach mounting system, which interfaces with that rear thread system. ETM flash hiders and brakes are available.
The Gemtech Neutron 7.62 possesses vent structures in its baffle array and end cap that are shown in the above test data to increase the rate of gas momentum transfer potential to atmosphere. The venting in the throat of the blast baffle, along with venting into each of the baffle annular cavities, reduces pressure stagnation. It is interesting to note that the baffle geometry in the Neutron 7.62 is somewhat similar to that in the Dead Air Nomad and Dead Air Nomad-Ti, with the two primary differences being the throat angle and porting geometry, which change the angle of incidence and stagnation pressure thresholds, respectively. The Gemtech Neutron 7.62 also has one less baffle than the Nomad series. Along with the ported blast baffle throat, these differences culminate in the Neutron 7.62 having a higher distal flow rate than the Nomad series; a design intention from Gemtech.
The gross suppression performance of the Gemtech Neutron 7.62 is similar to that of the SilencerCo Omega 300, which is longer. The Neutron 7.62 outperforms the first generation Dead Air Nomad-30, despite the Nomad having a larger diameter. The Gemtech Neutron 7.62 also outperforms the Q Trash Panda, which is both longer and larger diameter than the Neutron 7.62.
The Gemtech Neutron 7.62 outperforms the Otter Creek Labs Polonium-30, while being slightly longer. The Neutron 7.62 is significantly quieter than the Dead Air Sandman-S, while being both shorter and lighter. The Neutron 7.62 is eclipsed in performance by silencers like the Dead Air Nomad-Ti and the larger FOR Systems Monarch 7.62 and Q Thunder Chicken.
It is postulated that the Gemtech Neutron 7.62 may be subjected to somewhat extreme firing schedules without damage. However, PEW Science has not subjected the Neutron 7.62 to severe automatic firing schedules and encourages the user to contact the manufacturer for guidance prior to use in such applications. The silencer user manual from the manufacturer contains firing schedule recommendations.
In this review, the Neutron 7.62 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.
