During the Korean War several new vests were produced for the United States military, including the M-1951 (Chriss Body, 2002), "a vast improvement on weight, but the armor failed to stop bullets and fragments very successfully" (Military, 2004). For these reasons, Kevlar came into the picture. But Kevlar too had its failures because if "large fragments or high velocity bullets hit the vest, the energy could cause life-threatening, blunt trauma injuries" (Military, 2004). So the Ranger Body Armor was developed, which again was an improvement over the previous armor but still had its flaws: "it was heavier than the anti-fragment armor already worn by the infantry and offered less protection" (Military, 2004).
The newest armor issued by the United States military is known as Interceptor Multi-Threat Body Armor System. While it has its flaws, it protects the wearer from most low- to mid-velocity threats. Modern bullet-resistant vests made from woven Kevlar were tested by United States police forces in 1975. Since then several new fibers and construction methods for bulletproof fabric have been developed besides woven Kevlar, such as DSM's Dyneema, Akzo's Twaron, Toyobo's Zylon (now controversial, as new studies report that it degrades rapidly, leaving wearers with significantly less protection than expected), or Honeywell's GoldFlex. These newer materials are advertised as being lighter, thinner and more resistant than Kevlar, although they are much more expensive.
Both the Underwriters Laboratories (UL Standard 752) and the United States National Institute of Justice (NIJ Standard 0101.04) have specific performance standards for bullet resistant vests. The US NIJ rates vests on the following scale against penetration and also blunt trauma protection (deformation) (Table from NIJ Standard 0101.04):
|Armor Level||Protects Against|
(.22 LR; .380 ACP)
|This armor protects against .22 caliber Long Rifle Lead Round Nose (LR LRN) bullets, with nominal masses of 2.6 g (40 gr) impacting at a maximum velocity of 320 m/s (1050 ft/s) or less, and .380 ACP Full Metal Jacketed Round Nose (FMJ RN) bullets, with nominal masses of 6.2 g (95 gr) impacting at a maximum velocity of 312 m/s (1025 ft/s) or less.|
(9 mm; .40 S&W)
|This armor protects against 9 mm Full Metal Jacketed Round Nose (FMJ RN) bullets, with nominal masses of 8.0 g (124 gr) impacting at a maximum velocity of 332 m/s (1090 ft/s) or less, and .40 S&W caliber Full Metal Jacketed (FMJ) bullets, with nominal masses of 11.7 g (180 gr) impacting at a maximum velocity of 312 m/s (1025 ft/s) or less. It also provides protection against the threats mentioned in [Type I].|
(9 mm; .357 Magnum)
|This armor protects against 9 mm Full Metal Jacketed Round Nose (FMJ RN) bullets, with nominal masses of 8.0 g (124 gr) impacting at a maximum velocity of 358 m/s (1175 ft/s) or less, and 357 Magnum Jacketed Soft Point (JSP) bullets, with nominal masses of 10.2 g (158 gr) impacting at a maximum velocity of 427 m/s (1400 ft/s) or less. It also provides protection against the threats mentioned in [Types I and IIA].|
(High Velocity 9 mm; .44 Magnum)
|This armor protects against 9 mm Full Metal Jacketed Round Nose (FMJ RN) bullets, with nominal masses of 8.0 g (124 gr) impacting at a maximum velocity of 427 m/s (1400 ft/s) or less, and .44 Magnum Semi Jacketed Hollow Point (SJHP) bullets, with nominal masses of 15.6 g (240 gr) impacting at a maximum velocity of 427 m/s (1400 ft/s) or less. It also provides protection against most handgun threats, as well as the threats mentioned in [Types I, IIA, and II].|
|This armor protects against 7.62 mm Full Metal Jacketed (FMJ) bullets (U.S. Military designation M80), with nominal masses of 9.6 g (148 gr) impacting at a maximum velocity of 838 m/s (2750 ft/s) or less [provided the projectile hits the hard trauma plate insert]. It also provides protection against the threats mentioned in [Types I, IIA, II, and IIIA].|
(Armor Piercing Rifle)
|This armor protects against .30 caliber armor piercing (AP) bullets (U.S. Military designation M2 AP), with nominal masses of 10.8 g (166 gr) impacting at a maximum velocity of 869 m/s (2850 ft/s) or less [provided the projectile hits the hard trauma plate]. It also provides at least single hit protection against the threats mentioned in [Types I, IIA, II, IIIA, and III].|
Bomb disposal officers often wear heavy armor designed to protect against most effects of a moderate sized explosion, such as bombs encountered in terror threats. Full head helmet, covering the face and some degree of protection for limbs is mandatory in addition to very strong armour for the torso. An insert to protect the spine is usually applied to the back, in case an explosion blasts the wearer. Visibility and mobility of the wearer may be severely limited.
In terms of Kevlar, a IIA vest has around sixteen layers and a IIIA vest around thirty layers.
German standards allow for bullet impact depression of 20 millimeters on the mannequin's wax body under the vest; US standards allow for more than twice that (44 millimeters), which can be potentially lethal.
In addition, there are vests available for police dogs which offer a measure of protection for the animals.
An Aramid vest's material must not get wet, because it will lose its protective capability until dry again, or in some cases be permanently degraded (water acts as a lubricant, helping the bullet slip through between the fibres; ions may also weaken the structure of the fiber, see Kevlar for details). Most bulletproof vests have panels in sealed enclosures, but waterproofing is usually not perfect. Dyneema based vests do not have the same difficulties with water.
The Future of Bulletproof vests
In recent years advances in material science have opened the door to the old idea of an actual "Bulletproof vest" that will be able to stop handgun and rifle bullets without the assistance of heavy and cumbersome extra metal or ceramic plating. Researchers in the U.S. and separately in the Hebrew University are on their way to create artificial spider silk that will be super strong, yet light and flexible. Other research has been done to harness nano-technology to help create super strong materials that could be used in future bulletproof vest. In 2005 an Israeli company claimed  it was able to develop a nano material based on Tungsten Disulfide that was able to withstand shocks generated by a steel projectile traveling at velocities of up to 1.5 km/second. The material was also reportedly subjected to a shock pressures generated by the impacts of up to 250 tons per square centimeter. During the test the material proved to be so strong that after the impact the samples remained essentially identical compared to the original material. Spider silk bulletproof vests and nano based armor are, as to late 2005, still in the future but they give the hope that some day we might actually use the modern equivalent of the medieval armor.
United States Law 18USC931 provides that: (a) In General. Except as provided in subsection (b), it shall be unlawful for a person to purchase, own, or possess body armor, if that person has been convicted of a felony that is (1) a crime of violence (as defined in section 16); or (2) an offense under State law that would constitute a crime of violence under paragraph (1) if it occurred within the special maritime and territorial jurisdiction of the United States.
Many states have criminalized the use of body armor by convicted felons. In February of 1999, the late Russell Jones a.k.a. "Ol' Dirty Bastard" was arrested in California for possession of body armor by a convicted felon.
Curiously enough, bulletproof vests remain legal in many countries where firearms are heavily restricted, such as the UK. One exception is Australia, where body armor has been prohibited for some time, despite the low level of violent crime in that country and no instances of criminal use. This ban may have its origins in the late 19th century, when the iconic Australian outlaw and folk hero Ned Kelly used home-made armor with mixed results. While the steel armor worn by Kelly defeated the soft lead, low velocity bullets fired by police Martini-Henry rifles, it greatly restricted his movement.