Otter Creek Labs Infinity Vented 7.62 on the Arsenal SAM7R and Arsenal SAM7C 7.62x39mm AK-Pattern Rifles with 16.3-in and 12.6-in Barrels

The Infinity is a 30 caliber centerfire rifle silencer designed by Otter Creek Labs. The Infinity is intended to suppress many cartridges with projectiles appropriately sized to travel through the bore, and may be used with severe firing schedules. It has a 1.73-inch diameter and is 6.6 inches long without a mount. The silencer does not include any mounts; the proximal end of the Infinity is threaded 1.375-24 tpi to accommodate “HUB” compatible mounting systems. The silencer body is 3D-printed from Inconel 718 alloy and the retail package includes multiple heat-treated stainless steel end caps that change system behavior. The user may choose to install different end caps to achieve varying flow states appropriate for the combustion dynamics of the chosen cartridge and weapon system. With an end cap installed, the silencer weighs 20 ounces and with a 14x1mm LH direct-thread mount, weighs 21.8 ounces and is 6.8 inches long, as tested. The Otter Creek Labs Infinity can be obtained from Silencer Shop.

The testing and analysis presented in this Sound Signature Review are of the Otter Creek Labs Infinity with Vented 7.62 end cap on two different AK-pattern host rifles:

Arsenal SAM7R 16.3-in barrel milled receiver Bulgarian-pattern import.
Arsenal SAM7C 12.6-in barrel milled receiver Bulgarian-pattern import.

Both rifles are chambered in 7.62x39mm. Hornady American Gunner 123gr ammunition was used in the tests. The standard AK-pattern host weapon systems are described in Public Research Supplement 6.200.

Report Table of Contents:

Section 6.204.1 contains an abbreviated overall summary of Otter Creek Labs Infinity Vented 7.62 rifle silencer performance on AK-pattern rifle systems and a brief competitive overview.
Section 6.204.2 contains Infinity Vented 7.62 full-size 16.3-in barrel Bulgarian-pattern AK test results and analysis.
Section 6.204.3 contains Infinity Vented 7.62 12.6-in barrel Bulgarian-pattern AK test results and analysis.
Section 6.204.4 contains overall Suppression Rating comparisons of the Infinity Vented 7.62 with other systems, like the Dead Air Wolverine and Zastava Arms ZVUK, along with cross-platform comparisons with the universal Suppression Rating metric.
Section 6.204.5 contains a report summary and PEW Science laboratory staff opinions.

Summary: When paired with the 16.3-in barrel Arsenal SAM7R and fired with Hornady American Gunner 123gr 7.62x39mm ammunition, the Otter Creek Labs Infinity Vented 7.62 achieved a Suppression Rating™ of 32.1 in PEW Science testing. With the 12.6-in barrel Arsenal SAM7C, the Otter Creek Labs Infinity Vented 7.62 achieved a Suppression Rating™ of 33.4.
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.

6.204.1 Otter Creek Labs Infinity Vented 7.62x39mm AK-Pattern Rifle Performance Summary

With this report, the PEW Science Silencer Sound Standard continues 7.62x39mm AK-pattern rifle silencer performance evaluation. The test data and analysis herein covers the Otter Creek Labs Infinity equipped with its vented 7.62 end cap evaluated on two Bulgarian-pattern AK platform rifles with 16.3-in and 12.6-in barrels, respectively. This specific configuration of the Infinity silencer has also been evaluated in the following reports:

In the three reports linked above, two gross conclusions regarding performance of this specific Infinity configuration were noted:

When blast load input pressure and duration are both high, the vented 7.62 configuration of the Infinity exhibits the least robust personnel protection from blast overpressure in the free field, when compared to conventional Otter Creek Labs silencer designs.
When blast load input pressure remains high, duration is reduced, and jet diameter is also reduced, the vented 7.62 Infinity achieves balanced performance, albeit still lower than Otter Creek Labs silencers sized for the cartridge. Nominal reductions to its distal vent area may significantly increase protection of personnel from blast overpressure in the free field.

When examining a third case presented in this report (supersonic 7.62x39mm AK platform blast load input, with native jet diameter, lower combustion duration than 7.62 NATO, and lower pressure than 5.56 NATO), the following performance conclusion is noted:

The Otter Creek Labs Infinity with its vented 7.62 end cap becomes highly efficient. Personnel protection capability is shown to significantly increase. Blast overpressure hazard risk decreases, with operator protection increasing further by managing weapon-specific blast parameters (gas system dwell time). These conclusions are shown relative to other silencers evaluated on two AK platform rifles in Figure 1 and Figure 2, below (click to enlarge). Metrics shown are in terms of PEW Science Suppression Rating, which is a human risk metric calculated from raw free field blast overpressure test data. The calculated risk metrics for the unsuppressed cases are also presented.

Figure 1. Suppression Rating Comparisons of Otter Creek Labs Infinity Vented, Dead Air Wolverine, and Zastava ZVUK Using PEW-SOFT 7.62×39mm Supersonic 16.3-in barrel AK Test Data and PEW Science Analysis

Figure 2. Suppression Rating Comparisons of Otter Creek Labs Infinity Vented and Dead Air Wolverine Using PEW-SOFT 7.62×39mm Supersonic 12.6-in barrel AK Test Data and PEW Science Analysis

From the above 7.62x39mm AK-pattern rifle performance metrics, it can be concluded that these systems can be significantly hazardous to both the operator and bystanders, even when suppressed. Note the presented performance metrics are of only three silencers. Further AK-pattern rifle testing and analysis with other silencer models is forthcoming.

Several key observations can be made from the above:

The conventional curved and stepped cone baffle geometry, along with generous over-bore of the Dead Air Wolverine (6.201), is significantly outperformed by more modern hybrid designs, not only in gross suppression performance (blast overpressure protection in the free field), but also in back pressure generation. This conclusion is particularly striking on the longest dwell time rifle, the 16.3-in AK, in which personnel hazard from combined muzzle and breech blast with the Wolverine is characterized by a Suppression Rating close to 10; one of the most hazardous systems classified in the research.
While the gross flow rate and suppression performance of the Zastava Arms ZVUK (6.202) is significantly more advanced than the Wolverine utilizing design elements to include Purposely Induced Porosity (PIP), its early-time flow rate is reduced when compared to the vented 7.62 end cap configuration of the Otter Creek Labs Infinity. The shooter’s ear (operator) Suppression Rating differential in Figure 1 on the 16.3-in barrel AK is significant.
When examining performance on the 12.6-in barrel system that generates higher muzzle blast input pressure into the silencers but possesses significantly shorter dwell time than the 16.3-in barrel system, the performance increase when fielding a vented Infinity compared with a Dead Air Wolverine is extreme (Figure 2). This performance gap represents a significant increase in personnel protection from free field blast overpressure when fielding the Infinity.

Note that the data plotted in Figure 1 and Figure 2 are consolidated in a master chart in Figure 11 in Section 6.204.4 of this report.

The detailed 7.62x39mm AK-pattern rifle evaluations of the Otter Creek Labs Infinity silencer in its vented configuration follow.

6.204.2 Otter Creek Labs Infinity Vented 16.3-in Barrel Bulgarian AK-Pattern Rifle Sound Signature Test Results

A summary of the principal Silencer Sound Standard performance metrics of the Otter Creek Labs Infinity vented silencer on the 16.3-in barrel Arsenal SAM7R Bulgarian AK-pattern rifle 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 public PEW Science testing, research, and development with a membership, here. State-of-the-art public firearm sound signature testing and research conducted by PEW Science is supported by readers like you.

Table 1. Otter Creek Labs Infinity Vented 16.3-in Bulgarian AK Sound Metric Summary

6.204.2.1 SOUND SIGNATURES AT THE MUZZLE

Real sound pressure histories from a 6-shot test acquired with PEW-SOFT™ are shown below. Six cartridges were loaded into the magazine, the fire control group positioned to single-shot, and the weapon was fired until the magazine was empty. Only five shots are considered in the analysis. The signatures of Shot 6 are displayed in the data presentation but are not included in the analysis to maintain consistency with the overall PEW Science public dataset and bolt-closing signatures. The waveforms are not averaged, decimated, or filtered. The data acquisition rate used in all PEW Science laboratory sound signature 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 laboratory testing; the recognized industry leader in silencer sound research. For more information, please consult the Silencer Sound Standard.

The primary sound signature pressure histories for all 6 shots with the Otter Creek Labs Infinity vented silencer 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 6-shot test are shown in Figure 4a. In Figure 4b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shots 2 and 3.

Fig 3a. Otter Creek Labs Infinity Vented 7.62×39mm 16.3-in barrel Bulgarian AK Muzzle Sound Pressure Signature

Fig 3b. Otter Creek Labs Infinity Vented 7.62×39mm 16.3-in barrel Bulgarian AK Sound Pressure Signature

Figure 4a. Otter Creek Labs Infinity Vented 7.62×39mm 16.3-in barrel Bulgarian AK Muzzle Sound Impulse Signature

Figure 4b. Otter Creek Labs Infinity Vented 7.62×39mm 16.3-in barrel Bulgarian AK Muzzle Sound Impulse Signature

As discussed in previous reports, the Otter Creek Labs Infinity is a 30 caliber rifle silencer that is classified as a hybrid design in the PEW Science research taxonomy. More specifically, the Infinity is classified as a staged hybrid. Hybrid design silencers are those in which elements of both conventional and high flow rate silencers are used, coupled with other technology variations and staged elements to provide parametrically varied performance attributes. Such attributes include the ability to reduce early-time shock reflections while significantly altering the rate of proximal and distal venting. These silencers may allow for minimal reciprocating weapon functional influence, while at the same time significantly suppressing signature to the operator and bystanders. Hybrid designs span a large range of the market in both brand and performance in different combustion regimes. There also exist subcategories of this class of silencers that have been shown to demonstrate efficacy in multiple flow regimes. Discussion of these subcategories is outside the scope of this report. Other hybrid designs and staged hybrids include those from PTR, CAT, CGS, SilencerCo, Surefire, and others. For an overview of the three primary classes of rifle silencer designs, the reader is encouraged to review PEW Science Research Supplement 6.169.

The Infinity can be fielded in multiple end cap configurations:

Configuration 1: 5.56 bore (solid)
Configuration 2: 5.56 bore (vented)
Configuration 3: 7.62 bore (solid)
Configuration 4: 7.62 bore (vented)

When changing end caps, blast load propagation from the Infinity changes through the primary bore, as expected, but it also changes in the annular vent passages. This is significantly different than changing the end cap bore aperture in a conventional silencer design. As a staged hybrid, the performance of the Infinity is sensitive to both blast load input pressure and duration. In the vented 7.62 bore configuration (this report), the Infinity is highly efficient with moderate pressure intermediate rifle cartridges with minimal jet over-bore. The following combustion propagation behavior is observed in the above test data:

Peak blast overpressure amplitude is significantly reduced with expedient blowdown. Bolt carrier return to battery is somewhat delayed (Fig. 3a).
First-round-pop (FRP) onset is immediate and severe, but short lived (Fig. 3b). Quenching occurs slightly after peak accumulation (Fig. 4a). Subsequent shots in the string are not only lower amplitude, but possess initial jet durations with shorter positive phase.
Post-FRP behavior is consistent; momentum is significantly controlled after the second shot in the string (Fig. 4b).

PEW Science Research Note 1: The above behavioral traits of the Otter Creek Labs Infinity with its vented 7.62 end cap are in stark contrast to its behavior in previous evaluations. As discussed in the first section of this report, when blast load input pressure and duration are both high (7.62 NATO weapons), the vented 7.62 configuration of the Infinity exhibits the least robust personnel protection from blast overpressure in the free field, when compared to conventional Otter Creek Labs silencer designs. When blast load input pressure remains high, duration is reduced, and jet diameter is also reduced (5.56 NATO weapons), the vented 7.62 Infinity achieves balanced performance, albeit still lower than Otter Creek Labs silencers sized for the cartridge. Nominal reductions to its distal vent area may significantly increase protection of personnel from blast overpressure in the free field. The 7.62x39 suppression performance from the Infinity can be considered its “goldilocks” zone, in that the input blast pressure and duration envelope produces the most efficient performance for the silencer.

PEW Science Research Note 2: The FRP propagation behavior from this configuration of the Infinity, with this particular blast load input, highlight the specific pressure staging of its design. By giving access to additional flow paths in the silencer, the vented end cap also allows ancillary combustion propagation for a longer duration; the Infinity employs the most efficient use of its pressure staging through a manual change to its vent array. This is in contrast to fully passive pressure staging in technologies like CAT SURGE BYPASS and KAC PRT. In practicality, it is important to note that although the Infinity has severe FRP in this application, every shot from a silencer like the Dead Air Wolverine is more severe than even the Infinity’s FRP. Further details and performance comparisons of these metrics will be presented in a PEW Science Member Research Supplement for AK-pattern rifles.

PEW Science Research Note 3: Relative cross-platform comparisons of bystander and shooter risk are possible with the PEW Science Suppression Rating. The following systems exhibit similar blast overpressure risk to bystanders as the Otter Creek Labs 7.62 vented silencer on a 16.3-in barrel 7.62x39mm AK-pattern rifle, 1.0 meter left of the silencers’ end caps, in the free field:

PEW Science Research Note 4: It is extremely important for the reader to understand the Suppression Ratings are computed with free field test data, and are therefore universal when translating the weapon and operator to different environments without reflections. However, when the environment becomes complex with many reflecting surfaces, performance translation of different systems is not yet possible; sound field shapes and particle velocities result in varied blast wave time-of-arrivals, as well as changes of blast load angles of incidence; these variations change amplitude and phase waveform components. As a result of these inevitable environmental complexities, user impressions will vary, as both the shooter and bystander. Nonetheless, hazard reduction efficacy in the free field, as characterized by the Suppression Rating, holds. The Suppression Rating comparisons are the current state-of-the-art, and the most “apples to apples” sound suppression performance comparisons that currently exist. Further research is ongoing.

PEW Science Research Note 5: As in all semiautomatic weapon testing, a second pressure pulse originates from the ejection-port signature of the weapon and it occurs early enough in time such that its waves coalesce with that of the muzzle signature. However, in late time (at approximately 113 ms in Figure 3a) the mechanical noise of the bolt closing is observed. The pressure signature of Shot 6 also displays this event because this AK platform does not posses a “bolt hold open” feature after the sixth and final round is fired from the magazine.

PEW Science Research Note 6: The closing time of reciprocating systems is often directly related to the flow restriction of a silencer for a given weapon system. PEW Science has determined bolt closing time variation from the unsuppressed state to be a reliable indicator of silencer back pressure, with strong correlation with the PEW Science Back Pressure Metric, Omega and the alpha parameter. However, PEW Science has also determined that the indicator is unreliable upon upper receiver fouling. Sound signatures are not influenced by this fouling, as these kinematics occur in late time, after gas venting to atmosphere. Momentum transfer, weapon condition (upper receiver fouling), and other factors, can significantly influence bolt closing time. PEW Science urges the reader to exercise extreme caution if using the published bolt closing time to make determinations regarding silencer flow restriction (back pressure) or weapon system kinematics. This type of calculation may provide erroneous results, as the weapon condition at the time of each test is not published data. The time-scale duration showing bolt closing time is only published by PEW Science such that the signature data pedigree may be verified.

The shape, timing, and magnitudes of the early-time pressure pulses and overall shape of the impulse waveforms measured at the muzzle, from shot-to-shot, are relatively consistent. The consistency of the waveform amplitudes highlight the silencer’s overall sound performance consistency at the muzzle after the FRP, as well as the relative consistency of the tested automatic rifle firearm configuration.

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 Research Note 7: Note that the muzzle Suppression Rating of the Otter Creek Labs Infinity 7.62 vented on this 16.3-in AK-pattern rifle is 31.1 and the at-ear Suppression Rating is 23.4; different zones on the Suppression Rating Dose Chart. Although the operator protection is elevated over high back pressure models, there is still significant operator hazard on the standard 16.3-in Bulgarian-pattern AK rifle.

The signatures measured at the shooter’s ear are presented and analyzed in the full Member Version of this report.

The evaluation in this section covered the performance of the Infinity silencer on a Bulgarian-pattern AK rifle with 16.3 inch barrel. Reducing dwell time can reduce blast impulse to the piston system and delay bolt opening, thus lower the severity of blast overpressure from the weapon breech. This phenomenon is examined in the following evaluation of the Infinity on the 12.6-in barrel Bulgarian AK rifle.

6.204.3 Otter Creek Labs Infinity Vented 12.6-in Barrel Bulgarian AK-Pattern Rifle Sound Signature Test Results

A summary of the principal Silencer Sound Standard performance metrics of the Otter Creek Labs Infinity vented silencer on the 12.6-in barrel Arsenal SAM7C Bulgarian AK-pattern rifle is shown in Table 2. 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 public PEW Science testing, research, and development with a membership, here. State-of-the-art public firearm sound signature testing and research conducted by PEW Science is supported by readers like you.

Table 2. Otter Creek Labs Infinity Vented 7.62×39mm 12.6-in barrel Bulgarian AK Sound Metric Summary

6.204.3.1 SOUND SIGNATURES AT THE MUZZLE

The primary sound signature pressure histories for all 6 shots with the Otter Creek Labs Infinity vented silencer are shown in Figure 7a. The sound signatures of Shot 1 and Shot 2 are shown in Figure7b, in early time. The real sound impulse (momentum transfer potential) histories from the same 6-shot test are shown in Figure 8a. In Figure 8b, a shorter timescale is shown comparing the impulse of Shot 1 to that of Shots 2 and 3.

Fig 7a. Otter Creek Labs Infinity Vented 7.62×39mm 12.6-in barrel Bulgarian AK Muzzle Sound Pressure Signature

Fig 7b. Otter Creek Labs Infinity Vented 7.62×39mm 12.6-in barrel Bulgarian AK Muzzle Sound Pressure Signature

Fig 8a. Otter Creek Labs Infinity Vented 7.62×39mm 12.6-in barrel Bulgarian AK Muzzle Sound Impulse Signature

Fig 8b. Otter Creek Labs Infinity Vented 7.62×39mm 12.6-in barrel Bulgarian AK Muzzle Sound Impulse Signature

The Otter Creek Labs Infinity performance appears to be high pressure biased in this regime; its staged hybrid design gains efficiency as blast load input pressure increases for a given duration and jet diameter. When comparing performance on the shorter 12.6-in barrel, above, to the previously presented 16.3-in barrel:

Peak blast pressure amplitude increases, but not significantly (Fig. 7a).
Primary jet formation time and phasing are similar, but rarefaction happens sooner (Fig. 7b).
Gas velocity also increases, as expected. However, consistency increases and occurs earlier in the shot string (Fig. 8b).
Positive phase impulse is of somewhat shorter duration (Fig. 8a.)

In addition to the above four differences, breech blast is reduced due to the shorter dwell time. All of these factors result in the Infinity actually producing a slightly increased Suppression Rating 1.0 m left of the end cap, in the free field, when used on the shorter barrel AK system.

PEW Science Research Note 10: While the behavioral improvements when utilizing the shorter barrel Arsenal rifle with shorter dwell time are expected, the increased efficiency of the Infinity in this particular combustion regime is a key finding. Though the increase in muzzle Suppression Rating from 31.1 to 32.4 is not extreme, it is also not a decrease. This is in stark contrast to the behavior of the Dead Air Wolverine when moving from the standard barrel length to the short barrel length AK platform.

It is important to note that internal PEW Science testing has determined that the increase in Suppression Rating when shortening AK barrel lengths and dwell time is not isolated to the Otter Creek Labs Infinity. Research is ongoing.

PEW Science Research Note 11: Relative cross-platform comparisons of bystander and shooter risk are possible with the PEW Science Suppression Rating. The following systems exhibit similar blast overpressure risk to bystanders as the Otter Creek Labs 7.62 vented silencer on a 12.6-in barrel 7.62x39mm AK-pattern rifle, 1.0 meter left of the silencers’ end caps, in the free field:

PEW Science Research Note 12: Note that the muzzle Suppression Rating of the vented Otter Creek Labs Infinity on this 12.6-in AK-pattern rifle is 32.4 and the at-ear Suppression Rating is 24.9; again, different zones on the Suppression Rating Dose Chart. The high pressure efficiency of the Infinity, along with its reduced back pressure, contribute to a less severe operator hazard on the standard 12.6-in Bulgarian-pattern AK rifle when compared to the Dead Air Wolverine and Zastava Arms ZVUK. Note that the operator Suppression Rating increased from the 23.4 calculated with the 16.3-in Bulgarian rifle. This is largely due to reduced dwell time reducing the severity of ejection port (breech) blast loads.

The signatures measured at the shooter’s ear are presented and analyzed in the full Member Version of this report.

The initial summary from the beginning of the report is repeated below, with more information and a consolidated bar chart with all presented AK suppression performance metrics, to date .

6.204.4 Suppression Rating Comparison (7.62x39mm from the AK Platform)

Figure 11 presents a comparison of the PEW Science Suppression Rating of the Otter Creek Labs Infinity 7.62 vented silencer on the two tested AK-pattern rifles, along with the Dead Air Wolverine on the same rifles and the Zastava ZVUK on one tested rifle. The contents of the figure combine what was previously presented in Figure 1 and Figure 2. The standard PEW Science AK-pattern test host weapon systems are described in Public Research Supplement 6.200.

Figure 11. Suppression Rating Comparisons of Otter Creek Labs Infinity Vented, Dead Air Wolverine, and Zastava Arms ZVUK Using PEW-SOFT 7.62×39mm Supersonic AK Test Data and PEW Science Analysis

From the above 7.62x39mm AK-pattern rifle performance metrics, it can be concluded that these systems can be significantly hazardous to both the operator and bystanders, even when suppressed. Note the performance metrics presented are only of three silencers. Further AK-pattern rifle testing and analysis with other silencer models is forthcoming.

Several key observations can be made from the above:

Both the Zastava Arms ZVUK and Dead Air Wolverine are tributes to the legacy Soviet PBS system in gross exterior design envelope, with the ZVUK being significantly more advanced. The vented Otter Creek Labs Infinity is highly efficient in both suppression and flow rate, producing more balanced performance than both of those models. The following systems exhibit similar blast overpressure risk to bystanders as the Otter Creek Labs 7.62 vented silencer on a 16.3-in barrel 7.62x39mm AK-pattern rifle, 1.0 meter left of the silencers’ end caps, in the free field:
The following systems exhibit similar blast overpressure risk to bystanders as the Otter Creek Labs 7.62 vented silencer on a 12.6-in barrel 7.62x39mm AK-pattern rifle, 1.0 meter left of the silencers’ end caps, in the free field:
In operator protection, the early-time flow rate from the Infinity, along with the lower combustion pressure and duration of the 7.62x39mm cartridge, pay significant dividends. The Infinity’s efficiency in this regime allows it to eclipse ZVUK performance in blast overpressure protection to the operator by a significant reduction in breech blast load severity. The following systems exhibit similar blast overpressure risk to weapon operators as the Otter Creek Labs 7.62 vented silencer on the 16.3-in barrel AK platform system in the free field:
The following systems exhibit similar blast overpressure risk to weapon operators as the Otter Creek Labs 7.62 vented silencer on the shorter 12.6-in barrel AK platform with shorter dwell time, in the free field:

PEW Science Research Note 13: The Soviet AK-pattern rifle family may be suppressed by a variety of rifle silencer technologies. While historical precedent exists in aesthetics of design, mount system retention, and other characteristics, it is likely that the demanding (and hazardous) nature of the platform is best suited to be suppressed with advanced technologies to maximize personnel risk reduction. To date, hybrid designs like the Zastava ZVUK and the Otter Creek Labs Infinity demonstrate performance progress toward that goal. It is likely that there are additional existing hybrid designs and high flow rate designs that may show promise in balancing blast overpressure suppression and back pressure reduction on AK-pattern systems that may otherwise be relegated to use with traditional AR variants. This is a subject of future research.

As detailed in this report, signature suppression at the operator’s head is a function of both muzzle and ejection port signatures from AK-pattern weapon systems, as well as action noise components. Specific weapon system parameters, such as dwell time, can significantly influence operator risk.

Small arm weapon system suppression performance is a spectrum. The PEW Science Suppression Rating and the Silencer Sound Standard help quantify this spectrum for end users and industry, objectively.

6.204.5 Review Summary: Otter Creek Labs Infinity Vented 7.62 on the Arsenal SAM7R and Arsenal SAM7C 7.62x39mm AK-Pattern Rifles with 16.3-in and 12.6-in Barrels

When paired with the 16.3-in barrel Arsenal SAM7R and fired with Hornady American Gunner 123gr 7.62x39mm ammunition, the Otter Creek Labs Infinity Vented 7.62 achieved a Suppression Rating™ of 32.1 in PEW Science testing. With the 12.6-in barrel Arsenal SAM7C, the Otter Creek Labs Infinity Vented 7.62 achieved a Suppression Rating™ of 33.4.

As with all weapon systems, the user is encouraged to examine both muzzle and ear Suppression Ratings.

PEW Science Laboratory Staff Opinion:

The Otter Creek Labs Infinity is a severe-use mid-size 30 caliber rifle silencer with an advanced but flexible hybrid design. In the role of a 7.62x39mm AK-pattern rifle silencer, it is considered full-size. The silencer is user-configurable for different blast load flow states and allows the operator to adapt the system to a variety of host weapons. With a high early-time flow rate, the silencer is well suited to reduce system back pressure. When utilizing its vented 7.62 end cap that increases late-time flow rate significantly, the Infinity performs well on standard untuned AK rifles and produces balanced and efficient performance, regardless of barrel length. The Infinity is 3D-printed from Inconel alloy and is expected to offer significant durability for hard use.
The Otter Creek Labs Infinity is a 30 caliber rifle silencer that is classified as a hybrid design in the PEW Science research taxonomy. More specifically, the Infinity is classified as a staged hybrid. Hybrid design silencers are those in which elements of both conventional and high flow rate silencers are used, coupled with other technology variations and staged elements to provide parametrically varied performance attributes. Such attributes include the ability to reduce early-time shock reflections while significantly altering the rate of proximal and distal venting. These silencers may allow for minimal reciprocating weapon functional influence, while at the same time significantly suppressing signature to the operator and bystanders. Hybrid designs span a large range of the market in both brand and performance in different combustion regimes.
Two gross conclusions regarding performance of this vented 7.62 end cap Infinity configuration were noted in previous reports: (1) When blast load input pressure and duration are both high, the vented 7.62 configuration of the Infinity exhibits the least robust personnel protection from blast overpressure in the free field, when compared to conventional Otter Creek Labs silencer designs. (2) When blast load input pressure remains high, duration is reduced, and jet diameter is also reduced, the vented 7.62 Infinity achieves balanced performance, albeit still lower than Otter Creek Labs silencers sized for the cartridge. Nominal reductions to its distal vent area may significantly increase protection of personnel from blast overpressure in the free field. However, when examining a third case (the one presented in this report with supersonic 7.62x39mm AK platform blast load input, with native jet diameter, lower combustion duration than 7.62 NATO, and lower pressure than 5.56 NATO), the Infinity with its vented 7.62 end cap becomes highly efficient. Personnel protection capability is shown to significantly increase. Blast overpressure hazard risk decreases, with operator protection increasing further by managing weapon-specific blast parameters (gas system dwell time).
The Otter Creek Labs Infinity retail package ships without a mount. While this lowers cost and gives the user maximum flexibility, it also requires the user to remain diligent and be responsible for their mounting system choice. Appropriate mount for both practical field use case and blast load dynamics is paramount; the Infinity has a significant degree of early-time venting. This beneficial performance trait may be compromised through the use of mounts that induce undue blast load reflection, such as compensators like the "Cherry Bomb” and others. Use of such devices may increase the effective back pressure of a system by elevating the Alpha parameter; the early-time blast load impulse accumulation inside the first expansion chamber of the silencer. PEW Science encourages the user to contact the silencer manufacturer for a recommended mounting system for their requisite application(s).
The silencer is primarily constructed from Inconel 718 alloy; users may subject the silencer to abusive firing schedules without significant damage. PEW Science has not performed durability testing or evaluation of the Infinity. The user is encouraged to contact the manufacturer for use guidance.
In this review, the Otter Creek Labs Infinity performance metrics depend upon suppressing a supersonic centerfire rifle cartridge on two AK-pattern gas-operated rifles, which is an incredibly difficult 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 7.62x39mm cartridge are significant; the measured pressure and impulse magnitudes, and their durations, illustrate this fact. Silencer performance on automatic (reciprocating) rifles depends on many factors. Weapon configuration may significantly influence total suppressed small arm system performance.
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.

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Sound Signature Review™ (Free Version)

SSS.6.204 - Otter Creek Labs Infinity and 7.62x39mm Automatic AK-Pattern Rifles (Free Version)

Otter Creek Labs Infinity Vented 7.62 on the Arsenal SAM7R and Arsenal SAM7C 7.62x39mm AK-Pattern Rifles with 16.3-in and 12.6-in Barrels

6.204.1 Otter Creek Labs Infinity Vented 7.62x39mm AK-Pattern Rifle Performance Summary

6.204.2 Otter Creek Labs Infinity Vented 16.3-in Barrel Bulgarian AK-Pattern Rifle Sound Signature Test Results

6.204.2.1 SOUND SIGNATURES AT THE MUZZLE

6.204.3 Otter Creek Labs Infinity Vented 12.6-in Barrel Bulgarian AK-Pattern Rifle Sound Signature Test Results

6.204.3.1 SOUND SIGNATURES AT THE MUZZLE

6.204.4 Suppression Rating Comparison (7.62x39mm from the AK Platform)

6.204.5 Review Summary: Otter Creek Labs Infinity Vented 7.62 on the Arsenal SAM7R and Arsenal SAM7C 7.62x39mm AK-Pattern Rifles with 16.3-in and 12.6-in Barrels

PEW Science Laboratory Staff Opinion:

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