A ricochet ( ; ) is a rebound, bounce, or skip off a surface, particularly in the case of a

projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found in ...

. Most ricochets are caused by accident and while the force of the deflection decelerates the projectile, it can still be energetic and almost as dangerous as before the deflection. The possibility of ricochet is one of the reasons for the common firearms safety rule "Never shoot at a flat, hard surface." Ricochets can occur with ''any'' caliber, but short or round ricocheting bullets may not produce the audible whine caused by tumbling irregular shapes. Ricochets are a hazard of shooting because, for as long as they retain sufficient

velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...

, ricocheting bullets or bullet fragments may cause

collateral damage Collateral damage is any death, injury, or other damage inflicted that is an incidental result of an activity. Originally coined by military operations, it is now also used in non-military contexts. Since the development of precision guided ...

to animals, objects, or even the person who fired the shot.

Variables

Ricochets occur when a bullet or bullet fragment is deflected by an object rather than penetrating and becoming embedded in that object. Ricochet behavior may vary with bullet shape, bullet material, spin, velocity (and distance), target material and the angle of incidence.

Velocity

High-velocity rifle cartridges have higher probability of bullet penetration, because increased energy released by an identical bullet may fracture or temporarily melt the target at the point of impact. Alternatively, the same energy release may melt and/or disintegrate the bullet to reduce size and range of deflected particles. Ricochets are more likely with handgun cartridges and low velocity rifle cartridges such as

.22 Long Rifle The .22 Long Rifle or simply .22 LR or 22 (metric designation: 5.6×15mmR) is a long-established variety of .22 caliber rimfire ammunition originating from the United States. It is used in a wide range of rifles, pistols, revolvers, smo ...

Buckshot A shotgun shell, shotshell or simply shell is a type of rimmed, cylindrical (straight-walled) cartridges used specifically in shotguns, and is typically loaded with numerous small, pellet-like spherical sub-projectiles called shot, fired throu ...

and shotgun

slugs Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a smal ...

have similarly high ricochet probability, but ricochet range of smaller

shot Shot may refer to: Arts, entertainment, and media * ''Shot'' (album), by The Jesus Lizard *''Shot, Illusion, New God'', an EP by Gruntruck *'' Shot Rev 2.0'', a video album by The Sisters of Mercy * "Shot" (song), by The Rasmus * ''Shot'' (2017 ...

is lower than intact rifle or handgun bullet ricochets.

Bullet

Sectional density Sectional density (often abbreviated SD) is the ratio of an object's mass to its cross sectional area with respect to a given axis. It conveys how well an object's mass is distributed (by its shape) to overcome resistance along that axis. Sectio ...

, or mass of the bullet divided by the frontal area of the bullet, increases penetration of resistant surfaces. Elongated, spin-stabilized bullets fired from rifled firearms have greater sectional density than spherical bullets of the same diameter made from the same material; and elongated rifle cartridge bullets have greater sectional density than short bullets of the same diameter handgun cartridges. Bullet velocity is reduced by as much as 35% by each ricochet deflection, and velocity is further reduced by air resistance as cohesive bullet fragments often produce an audible whine tumbling after losing stability.

Target material

Comparative hardness and density determine the results of collisions with bullets. Bullets tend to penetrate low density materials like air with little deflection, although friction causes rotated projectiles to drift in the direction of rifling twist as the bullet falls through the atmosphere under the influence of gravity. Ricochets may be similarly deflected in the direction of rotation of the side of a spin-stabilized bullet contacting a resistant surface. Dense objects tend to prevail in collisions with less dense objects; so dense bullets tend to penetrate less dense materials, and dense materials tend to deflect light bullets. Resistance to penetration can be evaluated as the sectional density of the target material along the axis of bullet movement in front of the bullet. Metallic foil will be more easily penetrated than metal ingots, and sectional density of sheet metal increases as orientation of the sheet diverges from perpendicular to, toward parallel with, the bullet path. Bullets are more likely to ricochet off flat, hard surfaces such as concrete, rock or steel, but a ricochet can occur from irregular surfaces within heterogeneous materials including soil and vegetation. Uniformly soft, flexible materials like sand have a lower incidence of ricochet. Though it may not be intuitive, bullets easily ricochet off water; compare

stone skipping Stone skipping and stone skimming are considered related but distinct activities: both refer to the art of throwing a flat stone across the water in such a way (usually sidearm) that it bounces off the surface. The objective of "skipping" is t ...

Angle

The angle of departure, both vertically and horizontally, is difficult to calculate or predict due to the many variables involved, not the least of which is the deformation of the bullet caused by its impact with the surface it strikes. Probability of ricochet is highest from surfaces approximately parallel to the axis of bullet movement, and grazing ricochets typically depart the surface at a smaller angle than the angle of incidence (or approach). Probability of bullet penetration increases as the axis of bullet movement becomes perpendicular to the target surface; but penetration may create a depression or crater within which the bullet may ricochet more than once, possibly following the arc of the crater floor to depart the crater at a greater angle from the original surface than the angle of incidence. In an extreme case, a strong, cohesive bullet striking a nearly perpendicular elastic surface may ricochet directly back at the shooter. This situation is sometimes observed when hardened

armor-piercing bullet Armor-piercing bullets for rifle and handgun cartridges are designed to penetrate ballistic armor and protective shields intended to stop or deflect conventional bullets. Although bullet design is an important factor with regard to armor penet ...

cores fail to completely penetrate steel plate. The

United States Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, ...

noted increased ricochet range after adopting the M855A1

green bullet Green bullet, green ammunition or green ammo are nicknames for a United States Department of Defense program to eliminate the use of hazardous materials from small arms ammunition and from small arms ammunition manufacturing. Initial objectives we ...

with a larger steel core than the M855 bullet it replaced. Buckshot and subsonic bullets may be similarly reflected from rubber vehicle tires.

Consequences

Not all ricochets are accidental. Some bullets are fired to intentionally ricochet, just as in ricochets of some ball games like

basketball Basketball is a team sport in which two teams, most commonly of five players each, opposing one another on a rectangular Basketball court, court, compete with the primary objective of #Shooting, shooting a basketball (ball), basketball (appr ...

and

pool Pool may refer to: Water pool * Swimming pool, usually an artificial structure containing a large body of water intended for swimming * Reflecting pool, a shallow pool designed to reflect a structure and its surroundings * Tide pool, a rocky pool ...

Bullet trap A bullet trap (or pellet trap when used specifically for air guns) is a device to stop and collect projectiles fired at a shooting range to prevent overpenetrations and stray shots. Bullet traps typically use friction, impact or gradual deceler ...

s at indoor

shooting range A shooting range, firing range, gun range or shooting ground is a specialized facility, venue or field designed specifically for firearm usage qualifications, training, practice or competitions. Some shooting ranges are operated by military o ...

s often include durable steel plates to deflect bullets downward into a material intended to stop and capture the bullets.

Cannonball A round shot (also called solid shot or simply ball) is a solid spherical projectile without explosive charge, launched from a gun. Its diameter is slightly less than the bore of the barrel from which it is shot. A round shot fired from a la ...

s were often fired to strike the ground or water in front of their target in anticipation of

ricochets A ricochet ( ; ) is a rebound, bounce, or skip off a surface, particularly in the case of a projectile. Most ricochets are caused by accident and while the force of the deflection decelerates the projectile, it can still be energetic and almost ...

which would keep the projectile at an effective distance above the ground or water surface through massed troops or ships. The behavior of iron cannonballs documented during the era of

muzzle-loading A muzzleloader is any firearm into which the projectile and the propellant charge is loaded from the muzzle of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the modern (higher tech and harder to make) design ...

cannon A cannon is a large-caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder during ...

may be a useful approximation for a

BB gun A BB gun is a type of air gun designed to shoot metallic spherical projectiles called BBs (not to be confused with similar-looking bearing balls), which are approximately the same size as BB-size lead birdshot used on shotguns ( in diameter ...

or steel pellets fired from a

shotgun A shotgun (also known as a scattergun, or historically as a fowling piece) is a long-barreled firearm designed to shoot a straight-walled cartridge known as a shotshell, which usually discharges numerous small pellet-like spherical sub- pr ...

, but

inelastic collision An inelastic collision, in contrast to an elastic collision, is a collision in which kinetic energy is not conserved due to the action of internal friction. In collisions of macroscopic bodies, some kinetic energy is turned into vibrational ene ...

s between the various shapes and materials of high-velocity bullets and the objects they may strike make bullet ricochets less predictable than the intuitive

symmetry Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...

of low-velocity game spheres. The problem with unintentional ricochets is potential damage caused to objects outside the intended path of the bullet. A responsible shooter anticipates potential bullet interactions within a

cone A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines conn ...

of space around the aim point. The shooter is at the apex of the cone, and the cone is symmetrical around the intended bullet path. The angle of that cone may initially be defined by the accuracy of the firearm and the skill of the shooter; but any ricochet potential within the cone becomes the apex of a ricochet cone with a broader angle. The ground surface is a frequent source of ricochets. A bullet may be deflected more than once before it comes to rest. Damage potential of ricochets, like bullets, is proportional to the

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementa ...

of the bullet fragment and the

square In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90- degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length ad ...

of its velocity. Ricochet velocity is always lower than collision velocity, but may be close to collision velocity for small angles of deflection. Ricochet mass may be similarly close to original bullet mass for

full metal jacket bullet A full metal jacket (FMJ) bullet is a small-arms projectile consisting of a soft core (often lead) encased in an outer shell ("jacket") of harder metal, such as gilding metal, cupronickel, or, less commonly, a steel alloy. A bullet jacket usual ...

s or

s replacing soft

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, l ...

with solid copper or a steel core.

Frangible bullet Frangible bullets are intended to disintegrate into tiny particles upon target impact to minimize their penetration of other objects. Small particles are slowed more rapidly by air resistance, and are less likely to cause injury or damage to perso ...

s or lead core

varmint hunting Varmint hunting or varminting is the practice of hunting vermin — generally small/medium-sized wild mammals or birds — as a means of pest control, rather than as games for food or trophy. The targeted animals are culled because they are con ...

bullets are more susceptible to collision damage, and produce smaller ricochet fragments. Lower initial mass gives small fragment ricochets less damage potential, and distance of travel is reduced by more rapid loss of velocity from air resistance. Reduced ricochet range is one of the reasons the newer

.17 HMR .17 Hornady Magnum Rimfire, commonly known as the .17 HMR, is a rimfire rifle cartridge developed by Hornady in 2002. It was developed by necking down a .22 Magnum case to take a .17 caliber (4.5 mm) projectile. Commonly loaded with a 1 ...

round with its frangible bullet has gained popularity against the older non-fragmenting .22 WMR. Ricochets can be lethal. A notable death caused by ricochet was the hostage Katrina Dawson during the

Lindt cafe siege The Lindt Cafe siege was a terrorist attack that occurred on 15–16 December 2014 when a lone gunman, Man Haron Monis, held hostage ten customers and eight employees of a Lindt chocolate café in the APA Building in Martin Place, Sydney, ...

in December 2014, killed by a ricochet from a police bullet when tactical officers stormed the building.

References

{{Reflist

External links

"Ricochet Off Glass"
at National Crime Investigation and Training web site
.50 Cal Ricochet onto Shooter's Ear Muffs
–

YouTube YouTube is a global online video sharing and social media platform headquartered in San Bruno, California. It was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim. It is owned by Google, and is the second most vis ...

Ballistics