SSS.8.1.5 - Suppressed AR-15 Backpressure Hazards - SilencerCo Saker 556 vs. HUXWRX FLOW 556k MK18 Silencer Hazard Map Brief
/SilencerCo Saker 556 and HUXWRX FLOW 556K Models on the MK18 5.56x45mm 10.3-in Barrel Automatic AR15 Rifle - Hazard Maps
This Silencer Hazard Map Brief documents the free field blast overpressure hazards from the SilencerCo Saker 556 and HUXWRX FLOW 556k fielded on the 10.3-in MK18 AR-15 semiautomatic rifle firing M193 55gr 5.56 NATO ammunition, as evaluated in technical Report 6.53 and Report 6.83 and as tabulated in record numbers 7.1.53 and 7.1.82 in the Rankings, respectively.
The average Suppression Rating hazard contours at 1.6 m silencer end cap elevation from the instrumented blast test of the SilencerCo Saker 556 silencer computed with the PEW-SOFT HD Blast Hazard Prediction Tool are shown in Figure 1. Hazard contours for the HUXWRX FLOW 556k silencer are shown in Figure 2. The Suppression Rating hazard scale is shown in Figure 3. Ground-truth anchored Suppression Ratings from the technical reports 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.
8.1.5.1 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 Saker 556 silencer is 0.435. The FLOW 556k silencer has a jet stability index of 0.038.
8.1.5.2 SilencerCo and HUXWRX High and Low Backpressure 5.56 Suppression Hazard Map Observations:
The SilencerCo Saker 556 utilizes a traditional reflector baffle stack with no high flow rate features, no annular utilization, and no blast chamber or distal venting. The high jet stability index in the model, along with the relatively high muzzle Suppression Rating calculated from the test data, results in a focused hazard field, forward of the MK18 operator. The ejection port blast from the weapon system is elevated due to the high system back pressure, and the hazard contours near the shooter reflect this. Note that adjacent to the shooter, human risk decreases readily with distance.
The HUXWRX FLOW 556K uses Flow Through technology with significant early and distal venting. The silencer is shorter than the Saker 556. Its jet stability index in the model is significantly lower than that of the Saker 556, resulting in a broader hazard field forward of the operator. The ejection port blast from the weapon system is significantly less severe than from the Saker 556. However, adjacent to the operator, human risk does not diminish at as great a rate. The muzzle blast from this system is severe, subjecting bystanders to significantly more hazard.
Weapon system tuning may significantly influence the predicted hazards from the SilencerCo Saker 556 system shown in Figure 1. In the case of the extremely low back pressure HUXWRX 556k system shown in Figure 2, weapon system tuning may not appreciably influence the predicted hazard field. This comparison illustrates two extremes:
High back pressure traditional AR-15 suppression.
Low back pressure “ultra-high” flow rate suppression.
The user is encouraged to be mindful of these extremes. Modern silencer designs may provide less of a performance and hazard reduction compromise as technology advances.
fig 1. SilencerCo Saker 556 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. HUXWRX FLOW 556k 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 3. PEW Science Suppression Rating Scale
