SSS.8.1.20 - Multi-Caliber Silencer Hazards - Otter Creek Labs Universe-36 Silencer Hazard Map Brief
/Otter Creek Labs Universe-36 on 5.56 MK18 AR-15, .308 Bolt-Action, and 9mm HK MP5 - Hazard Maps
This Silencer Hazard Map Brief documents the free field blast overpressure hazards from the Otter Creek Labs Universe-36 multi-caliber rifle silencer fielded on the following weapon systems:
10.3-in barrel MK18 AR-15 semiautomatic rifle firing M193 55gr 5.56 NATO ammunition with the silencer’s solid 5.56 end cap.
20-in barrel .308 bolt-action rifle firing M80 149gr 7.62 NATO ammunition with the silencer’s solid 7.62 end cap.
8.9-in barrel 9mm SP5 submachine gun firing 147gr 9x19mm subsonic ammunition with the silencer’s solid 9mm end cap.
All three above cases are evaluated in technical Report 6.223 and the results tabulated in record numbers 7.1.255, 7.1.254, and 7.1.256 in the Rankings, respectively.
The average Suppression Rating hazard contours at 1.6 m silencer end cap elevation from the instrumented blast tests of the Universe-36 silencer computed with the PEW-SOFT HD Blast Hazard Prediction Tool are shown in Figures 1, 2, and 3. The Suppression Rating hazard scale is shown in Figure 4. Ground-truth anchored Suppression Ratings from the technical report are annotated 1.0 m left of the end cap (SR_muzzle) and 6 inches right of the shooter’s right ear (SR_ear). Computational parameters and blast overpressure hazard field observations are provided below.
8.1.20.1 PEW-SOFT HD Computational Model Parameters
PEW-SOFT HD code Version 2.2.7 Alpha was used.
Contour elevations are 1.6 m above grade. No reflecting surfaces, other than the ground, are present in the models.
Grid resolutions are 0.076 m (3 in).
The average semiautomatic jet stability index sigma_sa of the silencer is 0.131 on the MK18 and 1.0 on the SP5. The average bolt-action jet stability index sigma_b of the silencer on the .308 rifle is 0.157.
8.1.20.2 Otter Creek Labs Universe-36 Suppression Hazard Map Observations:
The Otter Creek Labs Universe-36 silencer is a hybrid design with high early time flow rate that controls combustion propagation well when using both a solid end cap and a low pressure and duration cartridge. When using supersonic intermediate and full size rifle cartridges, the Universe-36 produces broad risk field severity forward of the operator. With subsonic pistol cartridges, its jetting is highly controlled and focused resulting in a much less severe forward hazard field.
On reciprocating weapons, the high early time flow rate that reduces system back pressure will somewhat reduce ejection port blast hazards even with the use of a solid end cap. This is the case with both rifle and pistol cartridges. The use of a vented end cap may induce additional forward field hazard that could propagate rearward to the operator’s location.
On the MK18 with 5.56 NATO, the Universe-36 hazard field near the operator is comparable to many conventional silencers on the market (Fig. 1). With 7.62 NATO ammunition from a bolt-action rifle, personnel hazards are severe throughout the entire field (Fig. 2). Subsonic 9mm use of the Universe-36 on pistol caliber carbines or submachine guns produces a significantly less hazardous field (Fig. 3).
fig 1. Otter Creek Labs Universe-36 10.3-in MK18 AR-15 Free Field Hazard Map Produced by PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
fig 2. Otter Creek Labs Universe-36 20-in barrel .308 Bolt-Action Free Field Hazard Map Produced by PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
fig 3. Otter Creek Labs Universe-36 8.9-in 9mm HK MP5 Free Field Hazard Map Produced by PEW-SOFT HD Blast Hazard Prediction Tool using PEW Science Test Data
Fig 4. PEW Science Suppression Rating Scale
