An Exploratory Comparison of Water-Tamped and -Untamped Explosive Breaches: Practical Applications for the Tactical Community via a Pilot Study.

BACKGROUND: Tamping explosive charges used by breachers is an increasingly common technique. The ability to increase the directional effectiveness of the charge used, combined with the potential to reduce experienced overpressure on breachers, makes tamping a desirable tool not only from an efficacy standpoint for breachers but also from a safety standpoint for operational personnel. The long-term consequences of blast exposure are an open question and may be associated with temporary performance deficits and negative health symptomatology. PURPOSE: This work evaluates breaches of varying charge weight, material breached, and tamping device used to determine the value of tamping during various scenarios by measuring actual breaches conducted during military and law enforcement training for efficacy and blast overpressure on Operators. METHODS: Three data collections across 18 charges of various construction were evaluated with blast overpressure sensors at various distances and locations where breachers would be located, to assess explosive forces on human personnel engaged in breaching activities. RESULTS AND CONCLUSIONS: Findings indicate that water tamping in general is a benefit on moderate and heavy charges but offers less benefit at a low charge with regard to mitigating blast overpressure on breachers. Reduced overpressure allows Operators to stage closer to explosives and lowers the potential for compromised reaction time. It also reduces the likelihood of negative consequences that can result from excessive overpressure exposure and allow Operators to "do more with less" in complex environments, where resource access may be limited by logistic or other limitations. However, tamping in all instances improved blast efficacy in creating successful breaches. Future studies are planned to investigate tamping mediums beyond water and environment changes, whether tamping can be used to mitigate acoustic insult, and other explosive types.

The Role of Very Low Level Blast Overpressure in Symptomatology.

Blast overpressure exposure has been linked to transient, but measurably deteriorated performance and symptomatologies in law enforcement and military personnel. Overlapping sub-concussive symptomatology associated with the very low level blast overpressures (vLLB) but high sound pressure (<3 psi) associated with these exposures has largely been ignored. Notably, the current vLLB or acoustic literature has focused exclusively on auditory defects, and has not addressed the broader concerns of Soldier health and readiness. This work was prompted by reports of symptomatology such as headache, nausea, slowed reaction time, and balance/hearing complications among personnel undergoing frequent exposures to low overpressure accompanied by high acoustic pressures. To more fully address the consequences associated with low overpressure exposures (<3 psi), a pilot proof-of-concept study was implemented, and data was acquired at two sites on the Fort Benning grenade course range. Findings indicated overpressures ranged from 0.14 to 0.42 psi (0.97-2.89 kPa) at range 1 and 0.22-0.30 psi (1.52-2.07 kPa) on range 2 of the grenade course. Corresponding sound-meter data varied from 153.72 to 163.22 dBP. Headache and long think were the most frequently reported symptoms (3/6 instructors), with lightheadedness, ringing of the ears, restlessness, frustration, and irritability also increasing in 2/6 of the instructors post exposure. Long think (prolonged thinking), ringing of the ears, restlessness, and irritability were the most severe symptoms, with the highest reported post exposure value rating a 3 on the 0-4-point scale. We demonstrate that low-level repeated overpressure exposure can result in transient symptomatology that overlaps with sub-concussive like effects.

Shooter-Experienced Blast Overpressure in .50-Caliber Rifles.

BACKGROUND: Increasingly, military and law enforcement are using .50-caliber rifles for conflict resolution involving barricades, armor, vehicles, and situations that require increased kinetic energy. Consequences to the shooter resulting from the blast produced while firing these rifles remain unknown. We measured blast overpressure (OP) and impulse across various positions, environments, and weapon configurations to evaluate blast exposures to shooters. METHODS: Two separate, multiday, .50-caliber rifle training courses were evaluated to understand the blast exposure profile received from various tactical training scenarios, such as different firing positions (e.g., standing, prone, seated, kneeling) and locations (e.g., inside and atop vehicles, inside buildings, on hard/soft surfaces) across a variety of .50-caliber rifles with various barrel lengths, muzzle devices, and ammunition. Blackbox Biometrics, Generation 6, gauges were placed on operators to measure incident blast exposure. A total of 444 rounds fired from various .50-caliber rifles were evaluated to determine what OP was received by 32 different shooters. RESULTS: Our findings indicate OPs >4 psi are common and that muzzle devices are critical to blast exposure. Shooting positions closer to the ground experienced higher OP and impulse than did other positions. Suppressors mitigated blast effects well. CONCLUSION: When resources and operational parameters allow, suppressors are recommended, as are positions that move the shooter farther from reflective surfaces (standing preferred) to effectively reduce blast exposure. These shooter positions may require the use of supplemental rifle rests/tripods to provide sufficiently stable firing platforms from the standing position.