Brass Fetcher Ballistic Testing
Ballistic gelatin blocks are understandably criticized as not being real-world enough to simulate actual shooting events. It is true that ballistic gelatin is simulant material in that it simulates one particular tissue type. 10% gelatin is what is most commonly used in the ammunition industry and in law enforcement. The methodology developed by the FBI when they developed the 10% standard is scientifically sound, repeatable and reasonably affordable. It has enabled many people, including myself, a start in the study of wound ballistics. 20% gelatin is what is used mostly by western military powers for tissue simulation. The density of 20% gelatin is slightly higher than that of 10% gelatin and the most notable difference between the two mediums is that bullet penetration in 20% gelatin is approximately 70% that of the same bullet in 10% gelatin.
The behavior of a projectile upon high velocity impact with a fluid medium is largely governed by the density of that fluid. For a given velocity, the higher the density of the fluid, the greater the pressure acting at the nose. This is great news for expansion but bad news for keeping the bullet in one piece. Also, gelatin blocks are constantly criticized for not having bones embedded in them.
I fixed that problem by making Synbone-brand bone simulant plates and round bones part of the target array. Currently we have simulations for three shotlines available: a shot to the chest while the target is standing in a Weaver stance, a shot to the pelvic girdle and a frontal shot directed at the thigh bone. The targets consist of an array of materials with the same average density and thickness as you would find in the body of a 6-foot tall western male. All shots are filmed in using slow motion videography to visually assess the behavior of the bullets inside of the mediuim. Additionally, the initial velocities and the residual velocities are measured to determine the magnitude of the damage that was done to the simulated body part by the bullet.
Pictured above right (see Figure 3) is one of the calibration blocks—once the proper materials were chosen, the materials were calibrated using the weapons and ammunition specified in published autopsy data. The metric of success was either ‘exited body’ or not, and whether or not the bullet struck bone on its penetration through the target. Since a bullet strike to the heart is considered a critical hit, the actual test targets exclude the lung simulant pictured at the right end of the array.
Running has always been an integral part of land warfare. When people think of the ‘vital area’, they are thinking of the area which contains the –majority– of the vital areas in the human body. The unfortunate aspect of firearms is: marksmanship during a self-defense shooting is going to be significantly degraded from where it is on the range AND the bullet effects on the target will be nowhere near as impressive as they were on the waterjug in your backyard. You basically have a 40% chance of scoring a hit anywhere on the body of your attacker, if you are using a handgun.
So let’s look now at another vital area—the upper thigh. Specifically, the femur bone. Your attacker cannot run if this bone is broken. If your attacker cannot run, then they cannot run to cover or run to pursue you. Without a functional femur they are combat ineffective.
Hornady 230gr +P XTP impacting the femur simulant target. From A to F: bullet in flight, bullet before expansion, bullet at moment of expansion, bullet flexing bone before impact, bullet penetration of bone, bullet caught in fresh pig skin at rear of block.
Figure 8 shows the recovered bone from the shot above. Notice that the bone is still intact but badly fractured. It is possible that the tissue surrounding the bone could hold the bone together and allow limited function of the leg. But your opponent will not be running on this leg due to the increased stress on the fracture caused by the impact.
Many narrow shotlines exist on the human body. Among them is the pelvis when the target is standing in a Weaver stance. The bone plate that constitutes the pelvis varies in thickness throughout the pelvis but the 6mm thick bone plate from Synbone is thought to be a good average thickness. The intention of the Pelvis shot is to establish which projectiles function well when impacting a fluid target that is approximately 0.7” thick and then impacting a simulated bone.
Two examples from the slow motion videos will be presented below: the case of the 5.56x45mm 55gr FMJ (M193) and the 5.56x45mm 55gr Barnes DPX hollowpoint bullet. Both are shot out of a AR-15 with 20” barrel length and 1/12” twist.
The US M193. A 55gr FMJ that wounds through tumbling and fragmentation. Normally effective on deeper shotlines, the bullet is already through the target before it begins to yaw significantly.
The Barnes 55gr DPX as loaded by Cor-Bon. Even on such a narrow shotline, the bullet still expands and does significant damage to the bone simulant plate.
One of the things I found most fascinating about the first Simulated Shotlines series is the difference in damage done to the pelvis simulant bone plate by the different bullets. Let’s take a look at a few below.
For narrow shotlines, nothing beats an expanding bullet.
Click here for full report of Simulated Shotlines 1: 9mm Luger 124gr +P+ FMJ; 9mm Luger 124gr +P JHP; 45 ACP 230gr FMJ; 45 ACP 230gr +P JHP; 223 Remington 55gr FMJ; 223 Remington 55gr TSX and 12 Gauge Shotgun 00 Buckshot