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The above name is somewhat of a misnomer since most such protective vests are of little or no protective value against rifles regardless of the type, style, materials or caliber of the rifle ammunition (ammo) or even against handgun caliber ammo fired from a rifle. (The exception is the common .22 LR, which can usually be stopped by these vests even when fired from a rifle.) These vests are generally protective against handgun ammo fired from handguns--again, regardless of type, style, materials or caliber of the handgun ammo.
Some types of vests may be augmented with metal ( steel or titanium), ceramic or polyethylene plates that provide extra protection to vital areas. These "trauma plates" have proven effective against all handguns and some rifles, if the bullet actually hits the plate. These types of vests have become standard in military use, as advances in ballistic technology have rendered kevlar-only vests ineffective - The CRISAT NATO standard for vests includes titanium backing. Some vests are also designed to protect against knife attacks as well. The most recent U.S. military-issue body armour, the Interceptor Multi-Threat Body Armor System issued in the late 1990's, has small-arms protective inserts made of ceramic which can stop, shatter, and catch 7.62 mm rifle rounds.
A vest does not protect the wearer by deflecting a bullet. Instead, the individual layers of material catch the bullet and spread its momentumIn physics, momentum is a physical quantity related to the velocity and mass of an object. Momentum is the Noether charge of translational invariance. As such, even fields as well as other things can have momentum, not just particles. However, in curved s over a larger portion of the body, deforming the round and hopefully bringing it to a stop before it can penetrate into the body. While a vest can prevent a bullet from penetrating, the wearer can still be affected by the kinetic energyKinetic energy (also called vis viva or living force is energy possessed by a body by virtue of its motion. The kinetic energy of a body is equal to the amount of work needed to establish its velocity and rotation, starting from rest. Equations Definition of the bullet, with results ranging from bruises to serious internal injuries.
The oldest bulletproof fabric was made from silkSilk (SERICVS / Gr. sigma;ηρικoς ("silken") SERES / Gr. Sigma;ηρες ("Chinese") or alternatively < Ch. or ( pronounced "si") meaning "silk", the pictogram representing two strands of silk. is a natural fiber. This was capable of stopping some slow rounds from black powderBlack powder is a type of gunpowder discovered in the 9th Century and practically the only explosive known until the middle of the 19th Century. Used as an explosive and a propellant in firearms until the early 20th Century it was quickly superceded by ot guns. A more modern "flak jacket" was developed in World War IIWorld War II was the most extensive and costly armed conflict in the history of the world, involving the great majority of the world's nations, being fought simultaneously in several major theatres, and costing tens of millions of lives. The war was fough from nylonNylon Density1150 kg/m3 Electrical conductivity(σ)10-12 (m· ohm)-1 Thermal conductivity0. 25 W/(m·K) Nylon is a synthetic polymer, a plastic, invented on February 28, 1935 by Wallace Carothers at the E. du Pont de Nemours and Company of Wilmington, fabric but was only capable of stopping flak and shrapnelShrapnel in the strict sense, is shot deliberately included in a landmine or shell intended to be scattered by the explosion. The pellets in the Claymore mine used by the United States meet this definition. More loosely, the term is used to refer to any f, not bullets. Modern bulletproof vests made from KevlarKevlar (also produced by the Teijin Twaron company under the trade name Twaron is a type of high strength synthetic fiber first produced by the DuPont corporation in the early 1960s, following the work of Stephanie Kwolek. It is a registered trademark of were tested by United States police forces in 1975. Since then several new fibers for bulletproof fabric have been developed besides Kevlar, such as DSM's Dyneema, Akzo's Twaron, Toyobo's Zylon (now controversial, as new studies report it that degrades rapidly, leaving wearers with significantly less protection than expected), or Honeywell's GoldFlex. These newer fibres are advertised as being lighter, thinner and more resistant than Kevlar, although much more expensive.