SSS.8.1.1 - Introducing PEW-SOFT HD Silencer Hazard Maps
/The PEW-SOFT HD Blast Hazard Prediction Tool - Hazard Mapper
Section 6 of the Silencer Sound Standard contains hundreds of peer reviewed analytical test reports that, along with the Suppression Rating, changed the landscape of how the world viewed silencer performance.
The 2020 open letter in Section 1 of the Standard presented three main tenants describing the PEW Science vision:
Use existing nomenclature and terminology, where appropriate
Improve upon existing methodology, where possible and practical
Introduce new methods and combine them with established and peer reviewed science to improve the state of practice.
PEW Science used a strict interpretation of MIL-STD 1474E to demonstrate what can be done if it is implemented correctly and consistently, and just how useful pristine test data can be.
We think you can squeeze the lemon a little bit more. And sometimes, a picture is worth a thousand words. We think you’ll agree.
And don’t worry - the same Suppression Rating you know and love isn’t going away. Your view of it is being enhanced; and now it can be computed and displayed to you, everywhere:
Figure 1 shows you the famous Surefire SOCOM556-RC2 with its muzzle and ear Suppression Ratings when fielded on a standard MK18 as tested, calculated, and recorded in the Rankings. Those are ground truth anchors from the real free field test. What about the rest of the map? That’s a free field prediction based on ground truth using PEW-SOFT HD. The tool can also use reflecting surfaces to generate Silencer Hazard Maps relevant to the real life areas where you or your personnel may be operating. This report serves as a public introduction to these advanced PEW Science research capabilities.
Report Table of Contents:
8.1.1.1 - Dimensional Variations
8.1.1.2 - Free Field Data, and You
8.1.1.3 - PEW-SOFT HD Hazard Mapper
8.1.1.4 - MK18 Case Study: 556-RC2 vs. 556-RC3 vs FLOW 556k
8.1.1.5 - Reflections - Moving outside of the Free Field
8.1.1.6 - Conclusions and Acknowledgements
fig 1. Surefire SOCOM556-RC2 MK18 Free Field Hazard Map Produced by PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
Fig 2. PEW Science Suppression Rating Scale
8.1.1.1 The Varied Nature of Suppressed Small Arm Hazards
Both new and experienced users of small arms understand that nothing is constant. System accuracy, weight, repair, durability, loudness, choice of optic; your gear and the experience you have when fielding that gear are all subject to constant change.
There are two primary changes that are important to understand when fielding a suppressed weapon system, as they influence personnel hazard. These changes are:
Spatial - where are things happening? you and bystanders change location around the weapon system and your surroundings
Temporal - when are things happening? the frequency of your shooting changes, as do the blast dynamics of weapon systems
PEW Science mandated from the beginning that the only test data acceptable for use in the Silencer Sound Standard was to be acquired in the true free field, in accordance with MIL-STD 1474E, away from all reflecting surfaces other than the ground and the shooter themselves, with silencer end elevation of 1.6 m above grade. This was done in accordance with our vision outlined at the beginning of this report and in our open letter at the beginning of the Standard. But most importantly, it was done to maximize data utility.
8.1.1.2 Taking Full Advantage of Free Field Data
In the fields of Blast Effects Engineering, Protective Design and Analysis, and associated applied research, free field blast overpressure data is worth its weight in gold. Another name for free field blast overpressure data is uncontaminated data. All of the blast waveforms you have observed in the Silencer Sound Standard are free of contamination other than from ground reflection and shooter / weapon system reflections. Both of those categories of reflections are acceptable to us because they are standardized and practically dealt with during common use; these are real systems used by real people, and they are generally used near ground level.
Blast and acoustic wave reflections are nonlinear phenomena that vary based on amplitude, phase, angle of incidence, surface characteristics, duration, and a multitude of other factors. Reflections can increase hazard to personnel by increasing the amplitude of the returning blast overpressure waves. This is why your silencers sound louder to you indoors and why shooting without a silencer or with a loud silencer indoors can bring a significant risk of hearing damage and even traumatic brain injury (TBI). Blast load amplification due to reflections is real, and studying it in the context of suppressed small arms is important. But you have to walk before you can run.
It all starts with free field data. Once you have it, you can understand how it varies spatially, unencumbered by interference and contamination. You can calculate human risk metrics with it (like the Suppression Rating) which provides you with a universal “key” to system performance and personnel hazard that you can use to compare all suppressed systems on a level playing field. We have done that with Section 6 of the Standard and cataloged all records in the Rankings in Section 7 of the Standard.
The next step is two-fold; we will present to you how the hazards vary spatially (at many more locations than just at the “muzzle” and “ear”). We will now also apply test data to scenarios outside of the free field - introducing further complexity. PEW Science has now made these processes possible for suppressed weapon systems using existing free field test data, as outlined in this report.
8.1.1.3 What is the PEW-SOFT HD Hazard Mapper, and How does it Work?
“All models are wrong. Some models are less wrong than others... and some are certainly useful.”
We at the PEW Science Laboratory use the above quote weekly, if not multiple times per week; and it’s true. It is important to understand the limitations of analytical models when evaluating their efficacy in reproducing reality. The question becomes - “how good of an answer is good enough for your application?” This is a pragmatic question, the answer to which may change depending upon the level of effort involved.
The PEW Science PEW-SOFT HD Blast Hazard Prediction Tool and Hazard Mapper is a modeling tool that uses real test data as input to create predictive blast overpressure fields as output. Its functionality is described below:
What the Blast Hazard Prediction Tool is:
PEW-SOFT HD is a semiempirical engineering level computational analysis code.
It uses real free field test data as input. It considers the entire shot event; from before combustion takes place, until all the combustion has blown down from the system and all mechanical operation has ceased. All portions of the signature are used.
Developed fully in-house by the PEW Science Laboratory with internal funding.
The code is in continuous development.
What the Blast Hazard Prediction Tool can do:
PEW-SOFT HD can take any Silencer Sound Standard compliant test data from a specific silencer, weapon, and ammunition type combination, and use it as model input.
The code can generate predictive blast overpressure and impulse contours at any point in space produced by the weapon system input test data. The computational domain and grid resolution are user configurable.
At each point in space, full blast pressure history waveforms are generated. The domain and grid density is only limited by computing power (CPU cycles, RAM, and HDD space). The code runs on a personal computer, though it is multithreaded and scalable to other platforms.
Suppression Rating metrics (and any other hazard metric, risk metric, or signal analysis function) may be computed at each point in space in post-processing, if desired. Data fidelity is maintained at full microsecond (1.0 MS/s; 1 MHz) resolution from input to output.
Move from the free field to areas with reflections. The code can accept an arbitrary number of reflecting surfaces, reflectivity properties for each surface, and an arbitrary number of N-th order reflection path analyses. This means it can model a SWAT officer shooting in a hallway, a homeowner shooting in a bedroom, someone shooting outside next to a building, or next to a berm at a gun range, etc.
Two modules in the code have been developed; bolt-action and semiautomatic. The bolt-action module is the most advanced. This may seem counterintuitive to some readers, but bolt-action test data allows for the most isolated source terms from real test results. As a result, more model rigor (less assumptions) may be made using that type of model input.
The code generates an analytical jet model from the silencer’s distal orifice (where the bullet and gas come out). The shape and intensity of this jet are derived from real physical test measurements, including the PEW Science Omega Metric. Jet Stability Indexes are computed for each model run.
What the Blast Hazard Prediction Tool is not:
PEW-SOFT HD is not a computational fluid dynamics (CFD) code. CFD codes solve governing equations for mass, momentum, and energy at every point in the computational domain from analytically derived source energy terms. PEW-SOFT HD uses real blast loads measured in the free field and known weapon system parameters to back-calculate source terms and propagate them through the computational domain using wave propagation physics. It is a semiempirical engineering level modeling tool.
The code is not perfect (no model is). However, for free field modeling, uncertainty is very low near the ground-truth measurement locations (1.0 m left of the end of the silencer and 6 inches right of the shooter’s right ear, which are the MIL-STD free field test measurement locations used in the Silencer Sound Standard and the basis for the Suppression Ratings you see in the Rankings). Those two locations always anchor the models. When simulations are run with reflections, uncertainty increases, and anchor locations now express hazards from source wave propagations with additive Nth-order reflections. The results should be considered engineering level estimates.
The code is not freely distributable. It is an in-house tool used by the PEW Science Laboratory.
What the Blast Hazard Prediction Tool can’t do:
As of the time of writing, the code can only include reflecting surfaces that are X, Y, or Z planes (it can’t yet make diagonals, and it can’t yet make smaller objects like cars or trash cans, though it can be used to run problems incorporating those objects in simplified ways).
The code does not currently model diffraction or highly nonlinear blast load reflections from high amplitude waves (it can’t model high explosive detonation and resulting reflections. If you need tools for that or assistance with such scenarios, please contact us and we can help you with those types of problems).
Now check out how this thing works with some of your favorite silencers in two case studies:
8.1.1.4 Surefire SOCOM556-RC2 vs. RC3 vs. HUXWRX FLOW 556k Hazard Maps (Free Field)
This first case study presents PEW-SOFT HD Silencer Hazard Maps for three popular AR-15 rifle silencers, fielded on the standard untuned 10.3-in barrel MK18. Here are their accompanying free field blast testing reports, from which the PEW-SOFT HD model input data was obtained:
The computational domains have been kept constant, and the parametric details are annotated in the figures and explained below:
Each “world” is 3 m x 3 m (almost a 10 ft square). They are kept small for the purposes of this illustration. They are free field simulations (no reflecting surfaces have been added in the models other than the ground). Models with added reflecting surfaces are presented in Section 8.1.1.5.
The muzzle Suppression Rating (SR_muzzle) and ear Suppression Rating (SR_ear) you see labeled on the plots are the ground-truth metrics from the tests and the same detailed Ratings you see in the Suppression Rating Seal graphics at the top of each report in Section 6 and tabulated in the Rankings in Section 7.
In these particular simulations, the grid resolution used is 3 inches. That means there is a Suppression Rating calculation performed on a full pressure history waveform every 3 inches in space. That means there is a waveform just like you see presented in each test report generated at each point in space. The real waveforms are located at the muzzle and ear Rating locations. The rest are generated by the PEW-SOFT HD Hazard Mapper code.
The contour elevation (the distance into and out of the page) is 1.6 m above the ground. That is the location of the end of the silencer in every free field test. We wanted the demonstration of the code in this report to align with the Suppression Ratings you have already seen for these silencers on the MK18 (the elevation can be arbitrarily varied in the code, if desired).
The Average Jet Stability Index, sigma, is derived from physical measurements like the Omega Metric, and computed with some analytical engineering assumptions. The higher the Index, the more focused the jet out of the end of the silencer. The lower the index, the faster the jet breaks up, spreads out, and broadens.
All data is presented from standard 5-shot averages unless otherwise noted, just like the Suppression Rating. All Technical Test Report References (Section 6 of the Standard) and Rankings Record Number References (Section 7 of the Standard) are noted in each figure. All simulations are tied back to real free field test data, with references.
For a 5-shot average Hazard Map with the grid size and resolution in this case study, PEW-SOFT HD generates almost 8,500 full time regime blast pressure waveforms at microsecond resolution at a single 2D plane for analysis. This highlights the importance of pristine test data input and why PEW Science strictly adheres to Silencer Sound Standard test methodology (garbage in, garbage out). The below maps each use over 850,000,000 “dB” readings in their creation. Not just a single peak.
Notice anything interesting in the maps? We think you’ll find that the spatial hazard maps are reasonable models of real, known behavior. We hope they help you further understand what the Suppression Ratings have always been telling you.
8.1.1.4.1 Surefire SOCOM556-RC2
The Surefire 556-RC2 focuses blast, suppresses the overall blast field reasonably well, but induces some significant ejection port blast on the standard MK18. This builds upon what you already know from Report 6.52:
The Muzzle Suppression Rating of 35.4 and shooter’s ear Suppression Rating of 22.2 present in the Rankings are annotated on the map in Figure 3.
The RC2 is a relatively restrictive silencer design, though as a primitive hybrid, it is not as restrictive as something like an AAC M4-2000 or Otter Creek Labs Polonium, for example.
Per (2), the ejection port blast is relatively severe, the Jet Stability Index reflects a relatively focused jet, and the total hazard field is reasonable for a suppressed MK18. Note that this model is using 3-Prong mount test data (not WARCOMP mount test data). WARCOMP mount hazards are more severe due to blast load venting (leaks).
fig 3. Surefire SOCOM556-RC2 MK18 Free Field Hazard Map Produced with the PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
8.1.1.4.2 Surefire SOCOM556-RC3
The Surefire 556-RC3 certainly flows faster, but it also suppresses less. This only marginally helps reduce blast overpressure hazard to the shooter compared to the 556-RC2, and subjects bystanders to more severe hazard:
The Muzzle Suppression Rating of 27.2 and shooter’s ear Suppression Rating of 22.4 present in the Rankings are annotated on the map in Figure 4.
The RC3 is much less restrictive than the RC2. It is also a hybrid design, but possesses a distal vent array that expels combustion byproducts directly from its annulus. Note the lower Jet Stability Index.
Per (2), ejection port blast is somewhat reduced, but the more severe blast overpressure field in the forward hemisphere contributes to additional shooter hazard, resulting in almost the same overall risk to the operator as with the RC2. Note its jetting is broader than that of the RC2, which conceptually aligns with reality.
fig 4. Surefire SOCOM556-RC3 MK18 Free Field Hazard Map Produced with the PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
8.1.1.4.3 HUXWRX FLOW 556K
The HUXWRX FLOW 556K flows the fastest, but it flows so fast that the pressure field forward of the shooter is very severe. Immediately behind the weapon system, it is safer than with the Surefire silencers:
The Muzzle Suppression Rating of 25.8 and shooter’s ear Suppression Rating of 31.8 present in the Rankings are annotated on the map in Figure 5.
The FLOW 556k is even less restrictive than the RC3. Additionally, its distal gas velocity is exceedingly high. The silencer is shorter and has a full vent array; it is true “FLOW Through” technology, not a hybrid.
Per (2), ejection port blast is significantly reduced, and the gas velocity is so high that a significant proportion of blast energy is projected into the forward field. The severe jetting, corresponding to its very low Jet Stability Index, produces a blast overpressure field in the forward hemisphere that increases hazard when compared to both Surefire silencers. In the free field, the shooter is protected more than with a typical high back pressure silencer on a standard untuned MK18.
fig 5. HUXWRX FLOW 556k MK18 Free Field Hazard Map Produced with the PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
8.1.1.5 Surefire SOCOM556-RC2 vs. HUXWRX FLOW 556k Hazard Maps (Reflections)
In this second case study, the computational domain has been changed to include a wall located 0.53 meters to the left of the shooter (from the shooter’s point of view). This represents shooting near a wall, outdoors. Reflectivity parameters of the wall have been input into the model to represent a typical exterior wall with brick façade. The wall is not a perfect reflector, but it reflects much more than it absorbs. The code was instructed to run a 5th order reflection analysis, which was deemed appropriate to capture reflection behavior of only the ground and wall which are the only two major reflecting surfaces in the domain. Energy is dissipated with each reflection in accordance with the reflectivity of the surfaces and the reflection sequence for this particular one-wall simulation:
0th order analysis would be the direct path of the blast propagating to the source, and ending the simulation.
1st order analysis in this model is source —> wall —> target (one reflection; we already have the first ground reflection)
2nd order analysis adds source —> wall —> ground —> target (two reflections)
3rd order analysis adds source —> wall —> ground —> wall —> target (three reflections)
4th order adds four reflections, 5th order adds five reflections, etc. Each order of analysis adds a reflection.
How much more hazardous is shooting near a wall outdoors, instead of shooting in an open field? We can examine this case using Suppression Rating contours generated by PEW-SOFT HD 5th order reflection modeling output:
8.1.1.5.1 Surefire SOCOM556-RC2 (Near A WalL)
As shown in the free field test and free field Hazard Map shown in the previous section, the Surefire 556-RC2 focuses blast, but still induces some significant ejection port blast on the standard MK18. This hazard does not disappear when shooting near a reflecting surface; it is enhanced by blast load reflections off of the nearby wall, originating from both the ejection port and the muzzle blast from the silencer (Fig. 6). Note that the hazard contours “spread out” along the wall surface. This is due to severe localized blast overpressure reflection near the wall.
When compared to firing the RC2 MK18 system in the free field, shooting the system near a wall is estimated to decrease the Suppression Rating at the shooter’s ear by over 10 points. This is significantly more hazardous for the operator than the free field case. Bystanders, depending on their location on the map, may also be subjected to increased hazards.
fig 6. Surefire SOCOM556-RC2 MK18 Reflection Hazard Map (Shooter Near a Wall, Outdoors) Produced with the PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
8.1.1.5.1 HUXWRX FLOW 556K (NEar a Wall)
Again, the HUXWRX FLOW 556K has an extremely high distal flow rate that results in a severe forward pressure field. This produces intense reflections off of the nearby wall (Fig. 7). Note that the hazard contours “spread out” along the wall from the muzzle blast even more severely and further than in the case with the Surefire SOCOM556-RC2.
Coincidentally, the estimated shooter’s ear Suppression Rating again drops by approximately 10 points. Note that the 30 Suppression Rating contour line behind the shooter now extends further down (to the right, from the shooter’s point of view), which has put that area of the sound field with coordinates (-1 m , -1.2 m) in more danger than it was in the free field. Interestingly, as a comparison, that part of the sound field would now be less hazardous if using a Surefire 556-RC2! The spatial severity comparison of that part of the map has now flipped, when considering reflections. The overall hazard field, if shooting near a reflecting wall, is more intense with the HUXWRX FLOW 556k Flow-Through silencer than with the Surefire 556-RC2 hybrid design, just as it was in the free field.
fig 7. HUXWRX FLOW 556K MK18 Reflection Hazard Map (Shooter Near a Wall, Outdoors) Produced with the PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
If more surfaces were added (more walls, or even a roof, for example) the FLOW 556k hazard differential could potentially increase further. This type of analysis may underscore the need for consideration of distal gas velocity and gross flow rate when selecting a silencer system for use in close quarters. This may also help to visually illustrate why several users find “boomy” silencers like the HUXWRX FLOW 556k to create unpleasant conditions near reflecting surfaces.
8.1.1.6 Conclusions and Acknowledgements
As a shooter, you will operate in different environments alone or with other personnel present. Blast load hazards to you and others are real, and we hope this addition to the Silencer Sound Standard helps you further understand how these hazards may present in different environments and how different silencers and weapon systems vary in their production of hazards in those environments.
PEW Science continues free field testing, in accordance with the Silencer Sound Standard. With new and innovative tools like PEW-SOFT HD, hazards can be presented to consumers and end users more effectively. The effects of reflections, which are often neglected in silencer and suppressed weapon system performance analysis, can now be estimated analytically. Our free field test data continues to bear fruit, maximizing utility to silencer users and weapon system developers, worldwide.
The author would like to thank the following parties for their contributions to this work, without which it would surely not be possible:
Family and PEW Science Staff. Your unwavering love, support, and dedication to this research are its backbone.
Supporting PEW Science Members. Both your continued monetary and intangible support have truly helped to push the silencer industry forward, one test at a time. We are in your debt, always.
PEW Science Laboratory Clients. Your trust and relationships are valued and important.
Professional and Technical Mentors. Several decades of testing, research, and learning, with a lifetime to go. Thank you.
