SSS.8.1.28 - Suppressed MP5 Subgun Hazards - LayerX Strake 9 Silencer Hazard Map Brief
/LayerX Strake 9 on the HK SP5 9x19mm Subgun with 8.9-in barrel - Hazard Map
This Silencer Hazard Map Brief documents the free field blast overpressure hazards from the LayerX Strake 9 submachine gun silencer fielded on an 8.9-in barrel MP5 firing Speer Lawman 147gr ammunition, as evaluated in technical Report 6.231 and as tabulated in record number 7.1.267 in the Rankings.
The average Suppression Rating hazard contours at 1.6 m silencer end cap elevation from the instrumented blast test of the Layer X Strake 9 silencer computed with the PEW-SOFT HD Blast Hazard Prediction Tool are shown in Figure 1. The Suppression Rating hazard scale is shown in Figure 2. 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.
8.1.28.1 PEW-SOFT HD Computational Model Parameters
PEW-SOFT HD code Version 2.2.7 Alpha was used.
Contour elevation is 1.6 m above grade. No reflecting surfaces, other than the ground, are present in the model.
Grid resolution is 0.076 m (3 in).
The average semiautomatic jet stability index sigma_sa of the silencer is 0.52.
8.1.28.2 Layer X Strake 9 Suppression Hazard Map Observations:
The LayerX Strake 9 is a compact hybrid design that produces a high flow rate, at the expense of muzzle suppression performance. This is illustrated in the Hazard Map; the contours present in a shape more typical of a suppressed gas operated supersonic rifle system than a subsonic submachine gun system. For example, compare the map in Figure 1 of this brief to that in Figure 3 of Silencer Hazard Map Brief 8.1.20 for the Otter Creek Labs Universe-36. Note that the hazard contours near the shooter’s head are similar in amplitude, but the forward field is more hazardous with the Strake 9.
Blast load input into the silencer from the 8.9-in submachine gun is relatively low amplitude, though full power subsonic ammunition is used. Flow rate out of the end of the Strake 9 is relatively controlled, though high, and that manifests in the hazard field shape shown. FRP hazards are generally comparable to those in subsequent shots in the forward field, on average. FRP hazards to the operator may be more significant.
fig 1. LayerX Strake 9 HK MP5 9mm Subsonic 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
