Shooting on Steel is a Colission
By: Clark Vargas
Back splatter which is really secondary splatter, is hard to testify to because, just as billiard balls bank and ricochets, it is an inexact science.
The science however is governed the physic of collision and the derivations there from. In a perfect world, the problem could be analyzed on the basis of the theories for “Elastic and Inelastic Collisions of Solid Bodies” and the law of “Conservation of Energy”. From Elastic Collision theory one can theorize that the angle of incidence will be the angle of escape after the collision, but we are not in a perfect world.
The problem of the collision of bodies is a difficult one because in the analysis actual shooting surfaces, angles and hardness vary and the conservation-of-momentum principle is the only mechanical principle applicable to the problem. This principle alone is insufficient to determine the motion after a collision from the motion before the collision, since in the real world an underdetermined amount of energy will be converted into heat by deformation of the bodies during the collision, without violating conservation of energy. Energy is always conserved.
There are two extreme cases in which the problem is soluble and can be readily explained. One is the case in which we assume that no mechanical energy is dissipated as heat – kinetic energy as well as momentum is conserved. Such collisions are called perfectly elastic. Collisions between ivory billiard balls or glass balls fall approximately into this category. The other extreme category is that in which the bodies stick together after the collision. Such collisions are called perfectly inelastic. Collisions between balls of putty are likely to be in this category, and the collision between a bullet and a block of wood, in which the bullet remains embedded in the wood, certainly is.
In an elastic collision in which a particle strikes a much more massive particle at rest, bullet and a steel backstop, the velocity of the light particle is approximately reversed and that of the massive particle is unchanged. The extreme example is an elastic collision in which a particle strikes a smooth “fixed” plate perpendicularly. By a fixed plate we mean one rigidly attached to the earth, so the mass factor associated with the plate is the whole mass of the earth. In this case, the particle, bullet rebounds with exactly reversed velocity, ie: angle of incidence and escape are equal.
Consider the perfect inelastic collisions, in which one body has little mass and high velocity, the bullet, and the other mass large and no velocity, the backstop. Collisions of this type are ordinarily accompanied by pronounced deformation of one or both of the colliding bodies, and energy is lost in heat accomplishing this deformation. An inelastic collision may be visualized by imagining direct impact between a lead projectile and a sheet of soft steel, and the two bodies remain in contact after collision and therefore have a common final velocity or zero, all energy then is converted to heat or heat and splatter or less heat and splatter and varying degrees of fragmentation.
Bullets that hit a hard (Brinnel 300 to 500 Hardness) steel squarely will usually splatter and then break into fragments or deflect off the surface of the steel back stop or target. Depending on the bullet mass and velocity and the exact angle of impact, side splatter is predictable and some fragments may be sizable and can travel, a considerable distance (100-200ft) with sufficient velocity to cause injury.
Low velocity lead bullets and very heavily jacketed or solid metal (non-lead) bullets designed for deep penetration, and many types of shotgun pellets, may not side splatter or fragment at all, even when they hit the steel squarely and may instead deflect as whole bullet or pellet or rebound causing injury.
Any solid projectile can deflect (ricochet) in whole, un-fragmented if it glances off the slope or an edge of the steel. It will rebounds if it hits a pot mark, crater, or dimple in the steel. If further forward travel is not stopped by a range backstop swirl chamber or redirective plate, these whole bullets and whole shot pellets can travel 50 to 100 feet (depending on weight) and can cause injury.
The most common and frequent injuries from using steel back stops, or from using steel targets, are small cuts, scratches and bruises caused by fragments, not splatter, hitting the shooter or bystander at a distance normally inside of 10-yards. Even tiny fragments at close distance will cause serious eye injury if they hit the eye, and can also cause serious injury to soft unprotected parts of the body, neck or crook of the arm where surface arteries rises exist, etc.
It is commonly known in USPSA shooting circles that fragments rebounding, from medium-weight 140 to 180 grain high velocity handgun bullets hitting steel target have bounced back 150 feet (50 yards) and penetrated heavy denim clothing to enter the lower parts of a shooter’s body, requiring surgical removal of the bullet piece. Higher-velocity handgun bullets fired from long range shoulder firearms have even greater distance wounding potential.
Hard (Brinnell 300-500) steel targets and backstops are designed to deflect splatter and fragments in predictable directions, so that they can be stopped and contained by proper range surfaces backstops and/or deceleration chambers. The predictable “splatter zone” produced by hard steel back stops conversely creates a predictable “safe zone” within which shooters and others can stand. Relatively safety but not completely immune to ricochets and bounce backs.
The United States Practical Shooting Association (USPSA) practical shooting handbook. Rule 6.0 requires a minimum safe stage distance of 10-yards, 30-ft from any steel being engaged.
When a bullet hits an upright hard steel impact plate at a 90-degree angle (the easiest case to describe), the bullet usually splatters due to heat and fragments into many smaller pieces of bullet jacket and core. Provided the impact plate is flat and smooth, these fragments splatter off it at angles between 0 degrees (that is, flat along the surface of the plate) to 20 degrees from the surface of the plate. This 0-20 degree “splatter pattern” extends in 360 degree cone (like a clock face) from the impact point. The splatter pattern cone then extends up range and out to either side and down to the ground, and also up in the air from the impact point. Always wear eye protection when shooting specially on steel.
The size of the fragments, the velocity with which they splatter off the steel, and the resulting distance from the point of collision at which the fragments will cause injury in the splatter zone, will depend directly on the hardness of the steel, velocity and weight of the bullet and exact impact angle. Any type of jacketed ammunition will send splatter sideways at least 75 feet from an upright plate. Some calibers and ammunition types will create side splatter to 300 feet.
Because one cannot be sure of the exact distance to which dangerous side splatter will travel – and because this distance may vary from one shot to the next, depending on all the variables involved – one must accept that the side splatter on vertical steel can cause serious injury or death at any distance within the splatter zone. Because one cannot precisely judge the 20-degree angle of splatter – and because of the danger of “secondary splatter” bounce from sidewalls, one must keep back from the steel target or backstop in front of the impact point, at least 10-yards.
Berms, walls and range dividers are used to stop the side splatter from steel back stops and plate targets. The side berms, walls and dividers need to be continuous, unbroken surface so splatter cannot escape to injure someone on an adjacent area.
When sidewall dividers are placed close to the steel back stops and targets, the side splatter will eventually erode or cut through the barrier material. At close distances, where the velocity of the side splatter is still high, the continued impact from splatter will eventually cut through a masonry wall so wood or steel must face the wall and adjacent to steel back stops. If faced with wood, the wood will cut through, the wood will become filled with imbedded, jagged fragments of bullet jacket and bullet metal and these jagged fragments can cut someone who brushes against them and can also cause future “secondary splatter” to bounce off at unpredictable angels, possible causing injury to shooters and bystanders.
Depending on all of the variables, bullet construction weight, velocity, angles of impact with the steel backstop or target, steel clad, sidewalls may allow some side splatter to bounce off in the direction of the firing line – especially if the sidewalls are claded with hard-steel material and are positioned close to the point of impact, where the velocity of the side splatter is high.
Problems with secondary splatter from side walls are ameliorated by angling the barriers to deflect the secondary splatter safely downrange.
What happens when a bullet hits an angle plate back stops?
When a bullet hits a “down angle” plate back stop it usually fragments, sending a shower of splatter down off the plate. However, unlike the splatter pattern discussed for upright planes, the pattern from an angled plate is directed downward in a fan-shaped configuration, into the ground and slightly behind the plate in the direction of fire, and sideways 45-degrees more or less on both sides of the angles plate. Provided the range surface can safely absorb the splatter without producing “secondary splatter” in dangerous directions, the down angle Venetian blind back stop plate design serves to contain the splatter closer to the smash plate, reducing (but not eliminating) the safety hazard to either side of the target.
The converse is true for inclined plate backstops of various angles away from the firing line. In that case the back splatter is directed upwards usually behind a deflector plate into a swirl chamber and energy dissipator and collection trough.
With respect to debris flying back to a shooter the common back splatter has the least of energy and usually won’t travel very far.
Fragments that fly back from secondary rebound have more energy and are less frequent. The heights energy particle and the one that causes the greatest concern are the ricochet, if it continues in the general direction of travel or the rebound when it reverses the direction of travel and can come back, they can do damage at a distance and fortunately they are infrequent.
It is my opinion that range designers, range operators, Chief Range Officers, Training Officers, Match Directors and Stage Range Officers, worth their salt should be at least familiar with the safety aspects of shooting on steel to insure that safe shoots are conducted, by then on the facilities they operate.
Always remember, you can’t miss fast enough to win!