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 ...

. 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 a bullet 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 a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical q ...

, ricocheting bullets or bullet fragments may cause

collateral damage "Collateral damage" is a term for any incidental and undesired death, injury or other damage inflicted, especially on civilians, as the result of an activity. Originally coined to describe military operations, it is now also used in non-milit ...

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.

Buckshot A shotgun cartridge, shotshell, or shell is a type of rimmed, cylindrical (straight-walled) ammunition used specifically in shotguns. It is typically loaded with numerous small, spherical sub-projectiles called shot. Shotguns typically use a ...

and shotgun slugs have similarly high ricochet probability, but ricochet range of smaller shot is lower than intact rifle or handgun bullet ricochets.

Bullet

Sectional density, 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.

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 cores fail to completely penetrate steel plate. The

United States Army The United States Army (USA) is the primary Land warfare, land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of th ...

noted increased ricochet range after adopting the M855A1 green bullet 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 (appro ...

and

pool Pool may refer to: Bodies of water * 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 roc ...

Bullet trap A bullet trap (or pellet (air gun), 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 bullet, stray shots. Bullet traps typically use frict ...

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 milita ...

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 lar ...

s were often fired to strike the ground or water in front of their target in anticipation of ricochets 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 in which the user loads the projectile and the propellant charge into the muzzle end of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the modern designs of breech-loading fire ...

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 th ...

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 in shotguns ( in diameter) ...

or steel pellets fired from a

shotgun A shotgun (also known as a scattergun, peppergun, or historically as a fowling piece) is a long gun, long-barreled firearm designed to shoot a straight-walled cartridge (firearms), cartridge known as a shotshell, which discharges numerous small ...

, but inelastic collisions 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 () in everyday life refers to a sense of harmonious and beautiful proportion and balance. In mathematics, the term has a more precise definition and is usually used to refer to an object that is Invariant (mathematics), invariant und ...

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 In geometry, a cone is a three-dimensional figure that tapers smoothly from a flat base (typically a circle) to a point not contained in the base, called the '' apex'' or '' vertex''. A cone is formed by a set of line segments, half-lines ...

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 and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

of the bullet fragment and the

square In geometry, a square is a regular polygon, regular quadrilateral. It has four straight sides of equal length and four equal angles. Squares are special cases of rectangles, which have four equal angles, and of rhombuses, which have four equal si ...

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 usua ...

s or green bullets replacing soft

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

with solid

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

or a steel core. Frangible bullets 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 ...

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 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 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 an American social media and online video sharing platform owned by Google. YouTube was founded on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim who were three former employees of PayPal. Headquartered in ...

Ballistics