SSS.8.1.8 - Suppressed AR-10 Rifle Hazards - Dillon DRC308 Silencer Hazard Map Brief
/Dillon DRC308 on the SR-25 7.62x51mm 14.5-in Barrel Automatic Rifle - Hazard Map
This Silencer Hazard Map Brief documents the free field blast overpressure hazards from the Dillon DRC308 rifle silencer fielded on the 14.5-in KAC SR-25 semiautomatic rifle firing M80 149gr 7.62 NATO ammunition, as evaluated in technical Report 6.211 and as tabulated in record number 7.1.238 in the Rankings.
The average Suppression Rating hazard contours at 1.6 m silencer end cap elevation from the instrumented blast test of the Tisha 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.
8.1.8.1 PEW-SOFT HD Computational Model Parameters
PEW-SOFT HD code Version 2.2.4 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 0.041.
8.1.8.2 Dillon DRC308 Suppression Hazard Map Observations:
The Dillon DRC308 silencer is a hybrid design utilizing PIP with high early time flow rate and controlled late time flow rate. Blast load input into the silencer is relatively high amplitude from the 14.5-in rifle barrel. Blast load output from the silencer is moderately controlled, with somewhat unstable jetting.
Near-field severity forward of the operator is high relative to suppressed 5.56 NATO systems of similar barrel lengths, as expected. Near the operator, risk increases further and ejection port blast hazards contribute to this increased risk. The early time flow rate from the silencer is high enough such that ejection port blast hazards are reduced. Though further hazard reduction may be possible through weapon tuning, this system evaluation marks the introduction to SR-25 testing in the Standard. Further research is ongoing.
The hazard field from the DRC308 system is consistent, from shot to shot.
fig 1. Dillon DRC308 14.5-in SR-25 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
