Written by Michelle Henderson – Feb. 8, 2019
Bullet Traps and Terminal Ballistics
Many users of bullet traps do not know what to expect from them. Under estimates and over estimates are common and both can prevent the best utilization of the traps. When particles of lead are found on the floor of a new range, these questions always arise: “Is this trap safe? Is it installed properly? Is it an efficient trap? How close can we shoot? What safety precautions should be taken?”
With steel traps, most bullet particles found on the floor do not come from the bullet trap. The majority of lead particles found on the floor of a gallery range are created by bullets striking target carriers, target holders and target transport systems. Even the shaving of lead by revolvers must not be overlooked as a source of particles. We often hear a range officer proudly proclaim that nothing whatsoever escapes from their trap. That can only be interpreted in one of two ways. Usually it means they’re satisfied that nothing dangerous escapes from the trap. The other interpretation is that the range receives so little use they’re not aware of escaping particles. Unfortunately such remarks create an erroneous idea about bullet trap performance. When one expects 100% efficiency and discovers a piece of lead the size of a half-dollar at the firing line, alarm is understandable.
It is now possible to build a bullet trap so no lead particles can return towards the shooters from the bullet trap. Meggitt’s GranTrap™ is one such bullet trap. The trap is made from heavy steel support sheets which support the loose GranTex, rubber particles about 1/2-3/4″ in size, and is covered by a thin gum rubber curtain on the top. This patented design allows all bullets to enter the soft trap surface and be totally contained in one piece in the soft rubber media. This means no bullet particles can breakup and return towards the shooters.
Range operators should be concerned with three (3) kinds of particles: backsplatter; ricochet; and “floor sliders”. The latter is also called “skidders”, “bounders” or “skippers”. The term “slider” is also applied to bullets that are fired into the walls, ceiling or floor, and travel along these surfaces, leaving long streaks. In this discussion the term “slider” relates only to returning bullet particles. Backsplatter and ricochet particles travel under the initial energy imparted to the bullet. In contrast, floor sliders travel chiefly from gravitational energy. Except at very low velocity when a bullet hits an impenetrable object point blank, it is entirely broken up into particles that go off in a 360° pattern. As the impact surface is tilted away from vertical, more and more of the mass continues in the approximate direction that the bullet was originally traveling. In a steel bullet trap, these are the large pieces of lead that result.
However, some of the bullet particles leave a 360° cone pattern, and are the particles that make up the backsplatter. The exact amount and pattern is a function of many variables including the bullet alloy, the angle of the plate and the velocity of the impact. Let it suffice that the measure of ballistic efficiency is the relationship of the quantity of large massive pieces as compared to the quantity of fine dust and small shavings in the lead debris. For shooting range considerations, ricochet is considered to be any rebounding particle that is capable of inflicting property damage or bodily harm. Thus, a backsplatter particle could be considered ricochet if it traveled in the direction of the shooters, and if it contained sufficient energy to do harm.
Fortunately, the greater the energy in a particle, the greater the tendency for it to follow the originally aimed path of the bullet, i.e., in the direction of safe containment. The lower the energy in a particle, the more likely it is to behave as a billiard ball, and after a series of rebounds to get back to the firing line. Most people are surprised to learn that it is the relatively low velocity particle that can be the potentially dangerous ricochet.
By providing surfaces that will interrupt those particles traveling in a direction that could conceivably get back to the shooter, backsplatter particles are prevented from becoming ricochets. In an escalator trap, these surfaces are the sidewall fairings, the floor fairings and the diversion plate. In a venetian blind trap, the principal method is the anti-splatter edge along the leading edges of the impact plates. The closer these backsplatter interrupting members are located to the areas of bullet impact, the more backsplatter they will catch.
Unfortunately, in practical use the anti-splatter edges themselves receive a proportional share of the incoming bullets. Thus, instead of being the principal backsplatter eliminating feature, they become backsplatter and ricochet generating problems themselves.
The longer travel those backsplatter particles make, the larger proportion will pass over the various members intended to stop them. A very wide trap will result in more backsplatter particles escaping than a narrow trap. However, even in a five or six point trap, bullets fired into the lower extreme right or left side will result in noticeably more backsplatter escaping than those fired into the center or anyplace higher up on the trap.
Not so obvious, however, is the effect of the overtrap fairing. If the overtrap fairing is relatively short because of a low ceiling or ceiling baffle system, very little backsplatter results from the high shots that hit it. If the overtrap fairing is as long as it frequently is in a high ceiling range without a baffled ceiling system, it is inevitable that many bullets will hit its upper surfaces. This will result in backsplatter, some of which may end up on the floor. However, using an environmental bullet trap like the GranTrap equates to a range that is particle free from backsplatter and ricochets from the bullet trap. The bullets will not come back out of the soft rubber media and return towards the shooters. This is the safer design to consider. Click here to learn more about Meggitt’s wide variety of bullet traps.