SSS.6.131 - PTR VENT 2 and the Heckler and Koch SP5 9x19mm Subgun
/PTR VENT 2 on the HK SP5 9x19mm Subgun with 8.9-in barrel
The VENT 2 is designed and manufactured by PTR Industries. It is a 9mm centerfire submachinegun silencer intended for the 9x19mm cartridge with semiautomatic or fully automatic fire. The VENT 2 has a 1.5-inch diameter and is 7.6 inches long. The silencer may be attached to a variety of weapon systems depending on the user’s choice of mount; the included 1/2-28tpi direct thread mount increases the system length to 7.8 inches. Other mounting options are possible due to the rear of the silencer body being threaded with the SilencerCo Alpha pattern (1.125”-28 tpi threading). The entirety of the VENT 2 structure is monolithic and constructed from 3D Printed Titanium. The silencer weighs 8.5 ounces and the included direct thread mount weighs 1.8 ounces, for a total system weight of 10.3 ounces, as tested. The VENT 2 can be obtained from PTR Dealers.
PEW Science is an independent private testing laboratory and also the world’s only publicly funded suppressed small arms research cooperative. Testing, data analysis, and reporting is generated with funding provided by PEW Science members. Any test data that is generated with any portion of private funding contains this disclosure. The testing and data production for this Sound Signature Review was funded in part by PEW Science Project PEW-PTR-070-001-23. Therefore, data pertaining to the VENT 2 in this Sound Signature Review is published with the express written permission of PTR Industries Inc.
This Sound Signature Review contains single-test results using the PTR VENT 2 with the direct thread mount on the semiautomatic Hecker and Koch SP5 subgun, chambered in 9x19mm NATO with a 8.9-inch barrel. Speer Lawman 147gr ammunition was used in the test, in which its velocity was subsonic. The standard PEW Science HK SP5-A2 test host weapon system is described in Public Research Supplement 6.85.
Section 6.131.1 contains the VENT 2 test results and analysis.
Section 6.131.2 contains Suppression Rating comparisons of the VENT 2 with the Otter Creek Labs Lithium, HUXWRX CA$H 9K, Resilient Suppressors RS9, and GSL Phoenix fired on the Heckler and Koch SP5-A2.
Section 6.131.3 contains the review summary and PEW Science subjective opinions.
Summary: When paired with the 8.9-in barrel HK SP5-A2 with 80-deg locking piece and fired with Speer Lawman 147gr, the PTR VENT 2 mounted with the direct thread mount achieved a composite Suppression Rating™ of 62.7 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
6.131.1 PTR VENT 2 Sound Signature Test Results
A summary of the principal Silencer Sound Standard performance metrics of the PTR VENT 2 tested with the direct thread mount 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. PTR VENT 2 Sound Metric Summary
6.131.1.1 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, and the bolt returned to battery with an empty chamber. The HK MP5 family of submachineguns do not possess a bolt-hold-open feature. 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 dataset and bolt-closing signatures. 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 6 shots with the PTR VENT 2 are shown in Figure 1a. The sound signatures of Shot 1 and Shot 2 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 Shot 1, Shot 2, and Shot 3.
Fig 1a. PTR VENT 2 subsonic 9x19mm HK SP5-A2 Semiautomatic Subgun Muzzle Sound Pressure Signature
Fig 1b. PTR VENT 2 subsonic 9x19mm HK SP5-A2 Semiautomatic Subgun Sound Pressure Signature
Figure 2a. PTR VENT 2 subsonic 9x19mm HK SP5-A2 Semiautomatic Subgun Muzzle Sound Impulse Signature
Figure 2b. PTR VENT 2 9x19mm HK SP5-A2 Semiautomatic Subgun Muzzle Sound Impulse Signature
The PTR VENT 2 is a highly advanced and relatively lightweight pistol-caliber silencer specifically intended for use on submachineguns. Of particular note, the VENT series contains the PTR Purposely Induced Porosity (PIP) technology, along with other staged flow geometry, to significantly increase both early-time and gross flow rates. Notably, the technology also possesses significant sound suppression performance potential. There are several features of note in the above measured signatures demonstrating high suppression performance on this platform:
The gross free field pressure amplitudes are significantly suppressed (Fig 1a.) and decay expediently in early time.
The gas momentum accumulation is also significantly suppressed (Fig 2a.) with minimal first-round-pop (FRP) divergence occurring in early time.
PEW Science Research Note 1: In both amplitude and consistency, the VENT 2 produces signatures that indicate superior gross suppression performance to any other centerfire 9mm silencer system evaluated by PEW Science, to date. This extremely high level of performance is possible through significant surface area interaction with the PIP technology, facilitated by both primary jet flow through the vented core baffles and early venting from the first expansion (blast) chamber. Essentially, the PIP technology includes regions of metal foam lattice structures through which combustion gasses travel. In addition to significant turbulence and heat transfer, the porosity of the system implemented in the VENT 2 allows for gas expansion and dispersion forward of the muzzle, maintaining gross flow rate during the time regime of interest. The VENT 2 exhibits both high flow rate and high performance suppression. Interestingly, some of the design features in the VENT 2 share similarities with some features of CAT SURGE BYPASS; another technology exhibiting such combined performance attributes.
The suppression performance of the PTR VENT 2 on this platform is only approached by that of the GSL Phoenix (Review 6.86). The VENT 2 is able to meet or exceed the gross suppression performance of the Phoenix on this platform, and do so with a higher flow rate, further reducing operator hazard. This is notable, because this level of performance is atypical for silencers with high flow rates with subsonic ammunition. Furthermore, the VENT 2 is smaller than the Phoenix; it uses a significantly different technology to facilitate this level of performance. The PTR PIP technology is considered by PEW Science to represent one of the most significant advancements in the suppressed small arms state of practice. PEW Science evaluation of PIP in other cartridge combustion regimes is forthcoming.
There do exist other silencers that also possess high flow rates that have demonstrated efficacy on this platform, either in early time or in their gross gas dynamics. Such silencers include the Resilient Suppressors RS9 (Review 6.90) and the HUXWRX CA$H 9K (Review 6.97). Those two silencers also significantly reduce operator hazard on this weapon system, though not to the degree of the PTR VENT 2, and not with the overall suppression performance. In late time, the signatures from those two silencers are more noticeable to the operator. To bystanders, those two silencers are considerably louder than the VENT 2. The Otter Creek Labs Lithium (Review 6.102) does increase suppression performance over those silencers that are smaller than the VENT 2, though it does so with higher back pressure, increased hazard to the weapon operator, and significant FRP. Like the larger GSL Phoenix, the Lithium is a conventional baffle silencer.
The PTR VENT 2 completely masks FRP to bystanders on this weapon system.
PEW Science Research Note 2: As in most 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 85 ms in Figure 1a) the mechanical noise of the bolt closing is observed. The pressure signature of Shot 6 still displays this event due to the bolt not remaining open after the sixth and final round is fired from the magazine on the HK SP5-A2 weapon system. Nonetheless, the bolt is closing on an empty chamber.
PEW Science Research Note 3: The closing time of the HK SP5-A2 bolt is directly related to the flow restriction of a silencer used with the 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 with rifle cartridges, particularly on the MK18 weapon system. PEW Science Omega Metric and alpha parameter research in the subsonic 9x19mm combustion regime with the HK SP5-A2 and SP5K-PDW weapon systems is underway. Note that the PEW Science HK SP5-A2 possesses an 80-deg locking piece in its bolt carrier group, which may result in lower bolt carrier group rearward velocity than systems possessing standard angle locking pieces. This lower rearward velocity may result in delayed forward return velocity, when compared with other systems.
It is also important to note that PEW Science has determined bolt closing time to be an unreliable indicator upon upper receiver fouling in some weapon systems, such as the MK18 or M4A1. Sound signatures are typically not influenced by this fouling, as these kinematics occur in late time, after gas venting to atmosphere. Note that the roller-delayed blowback action of the HK SP5-A2 is significantly different than the direct gas impingement operated locked bolt action of the MK18. These factors, in addition to the difference in combustion regime amplitudes of supersonic 5.56x45mm and subsonic 9x19mm, result in a different influence of mechanical weapon noise to the total signature to which bystanders and the shooter is subjected.
As always, it is important to note that 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 semiautomatic firearm configuration.
PEW Science Research Note 4: Note that the muzzle Suppression Rating of the PTR VENT 2 with the direct thread mount is 62.6 and the shooter’s-ear Suppression Rating is 44.1; which are the different zones on the Suppression Rating Dose Chart. This demonstrates a typical performance attribute for silencers fielded on submachineguns. The gross suppression of a silencer, as well as its flow rate, influences the holistic signature on the standard HK SP5-A2 weapon system. The signatures measured at the shooter’s ear are presented below.
6.131.1.2 SOUND SIGNATURES AT SHOOTER’S EAR
Real sound pressure histories from the same 6-shot test 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 6 shots are shown in Figure 3. The primary sound signature history is shown in Figure 3a. A zoomed-in timescale is displayed in Figure 3b, 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 6-shot test are shown in Figure 4. Again, full and short timescales are shown.
Figure 3a. PTR VENT 2 subsonic 9x19mm HK SP5-A2 Semiautomatic Subgun Ear Sound Pressure Signature
Figure 3b. PTR VENT 2 subsonic 9x19mm HK SP5-A2 Semiautomatic Subgun Ear Sound Pressure Signature, Short Time Window
Figure 4a. PTR VENT 2 9x19mm HK SP5-A2 Semiautomatic Subgun Ear Sound Impulse Signature
Figure 4b. PTR VENT 2 9x19mm HK SP5-A2 Semiautomatic Subgun Ear Sound Impulse Signature Peaks
The sound signatures measured at the shooter’s ear from a suppressed roller-delayed blowback submachine gun are complex. However, there are key waveform features that allow for strict interpretation of various events occurring during the gunshot, and their contribution to the overall signature.
PEW Science Research Note 5: The PTR VENT 2 produces a signature at the shooter’s ear that is less hazardous than that produced with many other silencers on this weapon system. There are two related factors of note one can examine in the above signatures measured adjacent to the shooter’s head:
The pressure blow-down, from both the distal end of the silencer and the weapon breach, happens relatively quickly. The mechanical noise from weapon unlock during the firing cycle appears to be almost completely decoupled from those two blast loads (Figure 3b). That lack of load coalescence gives way to extremely minimal additional gas momentum accumulation after primary muzzle blast (Figure 4b). This is due to the high flow rate of the silencer.
The aforementioned blow-down speed due to the high flow rate from the VENT 2, coupled with its significant muzzle blast suppression, results in holistic gas momentum at the operator’s head that is not only lower amplitude than from any other silencer tested by PEW Science on this platform, but also more consistent. The user is encouraged to compare the impulse accumulation in Figure 4a of this article to that in Figure 4a of the GSL Phoenix article in Section 6.86.1.2. The Phoenix also has incredibly high gross muzzle blast suppression, but its ejection port blast is more severe and its pressure blowdown is of longer duration, which results in a longer positive phase duration of gas impulse accumulation. The difference in operator hazard with the two silencers is not drastic. However, at these high levels of suppression performance, on such a high-performance silencer host weapon like the HK MP5 platform, these performance differentiators are paramount for system characterization.
Maximizing the Suppression Rating to the weapon operator on the HK SP5 requires a combination of high flow rate and muzzle signature suppression. This balance has objectively been proven challenging to achieve.
PEW Science Research Peer Review Notes: Internal engineering reviews and external engineering peer reviews have been conducted of PEW Science data for the HK SP5 (MP5) system, focusing on weapon system kinematics. The roller movement and trunnion disengagement events are most likely the contributors at approximately 32 ms (Figure 4b) . Note that the bolt head is able to move prior to roller disengagement. Late-time event kinematics, such as cartridges being stripped from the magazine and the bolt returning to battery have also been verified (Figure 1a, 85 ms and Figure 3a, 83 ms).
Due to the relatively low pressure amplitude and duration of subsonic 9x19mm combustion compared with supersonic 5.56x45mm combustion, the influence of the above signature factors on the holistic system signature, especially to the shooter, is more significant.
PEW Science Research Note 6: Like the case at the muzzle and to bystanders, the FRP from the PTR VENT 2 at the shooter’s ear on this weapon system is significantly suppressed.
6.131.2 Suppression Rating Comparison (Subsonic 9x19mm from the HK SP5-A2)
Figure 5 presents a comparison of the PEW Science Suppression Rating of the PTR VENT 2 with the direct thread mount to that of the OCL Lithium, HUXWRX CA$H 9K, Resilient Suppressors RS9, and GSL Phoenix on the HK SP5-A2 system. The standard PEW Science HK SP5-A2 test host weapon system is described in Public Research Supplement 6.85.
Figure 5. Suppression Rating Comparisons of the PTR VENT 2 with the Otter Creek Labs Lithium, HUXWRX CA$H 9K, Resilient Suppressors RS9, and GSL Phoenix on the HK SP5-A2, Using PEW-SOFT 9x19mm Subsonic Test Data and PEW Science Analysis
The PTR VENT 2 induces a nominally lower hearing damage risk potential to bystanders than does the GSL Phoenix (6.86). When compared to the Otter Creek Labs Lithium (6.102) and Resilient Suppressors RS9 (6.90), the VENT 2 is significantly quieter.
Both the HUXWRX CA$H 9K (6.97) and the the RS9 possess very high effective flow rates for this platform and reduce operator hazard from ejection port blast, significantly. However, the VENT 2 also possesses a very high flow rate and not only reduces ejection port blast, but significantly suppresses muzzle blast. The combination of holistic suppression performance is so great with the PTR VENT 2 on this platform that it reduces operator hazard even further than than does the CASH 9K. With the muzzle Suppression Rating of the VENT 2 approaching almost two categories less severe than the CASH 9K, the difference in overall hazard with the two silencers on this weapon system, in multiple environments, is extremely significant.
Essentially, the PTR VENT 2 produces a gross sound field on this weapon system similar to that of the GSL Phoenix, with a higher flow rate, in a smaller design envelope. This performance is notable.
The PEW Science Suppression Rating quantifies inner ear damage risk. Human perception of sound may, or may not, always correlate. More detailed information regarding this phenomenon is presented periodically in PEW Science Member Research Supplements.
The signature to which the shooter’s ear is subjected is a function of both ejection port and muzzle signature. When the silencer’s endcap is in closer proximity to the shooter, the severity is increased. The coalescing of the ejection port overpressure with the primary muzzle blast may exacerbate the severity of the signature at the shooter’s head position. It is not ejection port signature, alone, that dictates the signature measured at the shooter’s head position.
Although the published suppressed HK SP5 dataset is limited, two significant conclusions drawn in previous articles once again hold true in this data and analysis:
The roller-delayed blow back MP5 operating system is still a blow back system. The delay, even when maximized with the 80-deg locking piece, still does not completely eliminate gas sensitivity during suppressed use. Silencer back pressure still influences the signature at the shooter’s ear on this suppressed weapon system.
The Flow-Baffles in the HUXWRX CA$H 9K and the early-time venting in the Resilient Suppressors RS9 significantly reduce back pressure. The suppression performance of those two silencers to the shooter in the subsonic pistol cartridge regime is notable, and the MP5 is gas sensitive enough for their back pressure reduction to have efficacy. The data presented with the PTR VENT 2 in this article further illustrates the benefit of high flow rate designs, even on the pistol-caliber roller-delayed blow back system.
Further study of the suppressed roller-delayed blow back system is a subject of future PEW Science research.
6.131.3 Review Summary: PTR VENT 2 on the HK SP5 9x19mm Subgun with 8.9-in barrel
When paired with the 8.9-in barrel HK SP5-A2 with 80-deg locking piece and fired with Speer Lawman 147gr, the PTR VENT 2 mounted with the direct thread mount achieved a composite Suppression Rating™ of 62.7 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 PTR VENT 2 is a full size 9mm silencer that exhibits significantly high sound signature suppression performance and low backpressure. Although it is intended for use on submachineguns, at 8.5 ounces and 7.6 inches long with no mount, it is close in size to many full size 9mm pistol silencers. The performance of the Purposely Induced Porosity (PIP) technology in the silencer, along with other portions of its design, is notable and represents further 3D-printed advancement in the suppressed small arms state of practice.
The PTR PIP technology, along with other staged flow geometry in the VENT 2, significantly increases both early-time and gross flow rate through the silencer. In both amplitude and consistency, the VENT 2 produces signatures that indicate superior gross suppression performance to any other centerfire 9mm silencer system evaluated by PEW Science, to date. This extremely high level of performance is possible through significant surface area interaction with the PIP technology, facilitated by both primary jet flow through the vented core baffles and early venting from the first expansion (blast) chamber. Essentially, the PIP technology includes regions of metal foam lattice structures through which combustion gasses travel. In addition to significant turbulence and heat transfer, the porosity of the system implemented in the VENT 2 allows for gas expansion and dispersion forward of the muzzle, maintaining gross flow rate during the time regime of interest. The VENT 2 exhibits both high flow rate and high performance suppression. Interestingly, some of the design features in the VENT 2 share similarities with some features of CAT SURGE BYPASS; another technology exhibiting such combined performance attributes.
The PTR PIP technology is considered by PEW Science to represent one of the most significant advancements in the suppressed small arms state of practice. PEW Science evaluation of PIP in other cartridge combustion regimes is forthcoming.
The included direct thread mount is easy to install in the VENT 2, and possesses hex-wrench features on the exterior. The mount may be removed and other mounts compatible with the so-called “SilencerCo Alpha” threading system may be installed. This feature allows the VENT 2 to be used with a variety of weapon systems.
In addition to fixed-barrel weapons, it may be possible that the VENT 2 may be used on semiautomatic handguns. The use of a silencer on such a weapon, for example, on a modified tilting-barrel Browning action, may often be accomplished through the use of an inertial decoupler assembly. PEW Science has not evaluated the VENT 2 in such a configuration. In general, PEW Science recommends the user contact both the silencer manufacturer and weapon manufacturer prior to creating and operating a suppressed weapon system from these components. Flow dynamics, system mass, and mechanics may significantly influence reliability, performance, and operational longevity of such systems.
In this review, the PTR VENT 2 performance metrics depend upon suppressing a subsonic centerfire pistol cartridge on a roller-delayed blowback submachinegun. While the sound signature of such cartridges can be suppressed to levels that may result in the desire of the shooter and bystanders to not wear hearing protection, PEW Science encourages the reader to remain vigilant with regard to all subsonic pistol cartridge suppression claims. The gas volume and combustion products created by firing a subsonic centerfire pistol cartridge such as 9x19mm are still significant; the measured pressure and impulse magnitudes, and their durations, illustrate this fact. Silencer performance on automatic (reciprocating) weapons depends on many factors. Weapon configuration may significantly influence total suppressed small arm system performance.
The hearing damage potential of subsonic submachinegun use is not insignificant. PEW Science encourages the reader to consider the Suppression Rating when deciding on an appropriate silencer and host weapon combination for their desired use.
