SSS.8.1.14 - Suppressed AR-15 Rifle Hazards - CAT ST Silencer Hazard Map Brief
/Combat Application Technologies CAT ST on the M4A1 Mid-Gas 5.56x45mm 14.5-in Barrel Automatic AR15 Rifle - Hazard Map
This Silencer Hazard Map Brief documents the free field blast overpressure hazards from the CAT ST silencer fielded on the 14.5-in M4A1RIII AR-15 semiautomatic rifle firing M193 55gr 5.56 NATO ammunition, as evaluated in technical Report 6.217 and as tabulated in record number 7.1.248 in the Rankings.
The average Suppression Rating hazard contours at 1.6 m silencer end cap elevation from the instrumented blast test of the CAT ST 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) in Figure 1. Computational parameters and blast overpressure hazard field observations are provided below.
8.1.14.1 PEW-SOFT HD Computational Model Parameters
PEW-SOFT HD code Version 2.2.6 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 CAT ST is 1.0.
8.1.14.2 CAT ST Suppression Hazard Map Observations:
The CAT ST silencer is a full size, 1.6-in diameter hybrid design rifle silencer using CAT SBX technology. The ST model possesses relatively high early time flow rate, though not as high as some previous generation CAT 5.56 rifle silencer models. Its late time distal flow rate is low and extremely controlled. The CAT ST may be considered somewhat “higher back pressure” than previous generation models. Blast load input into the silencer is relatively high amplitude from the 14.5-in rifle barrel. Blast load output from the silencer is very highly controlled, with the ST producing a stable jet as shown in Figure 1.
Near-field severity forward of the operator is significantly less intense and less hazardous than near the ejection port. It is important to note that the model used to produce the Hazard Map includes symmetry about the horizontal axis; the risk to the operator’s left should be viewed as conservative, as the ejection port is on the right side of the weapon system. The operator risk is highly driven by ejection port blast from the untuned M4 rifle used in the test. Far field severity is relatively low, compared to most suppressed 5.56 rifle systems.
The CAT ST produces a relatively consistent hazard field from the first shot to the last shot. Blowdown momentum is significantly controlled.
fig 1. CAT ST 14.5-in M4A1 AR-15 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
