Standards set by the National Institute of Justice (NIJ)--a division of the Department of Justice--classify bulletproof vests by the amount of protection the armor provides. Type IIA body armor--the lowest rated--resists handgun projectiles up to 9 mm or 40 caliber.
Type II resists both high-velocity 9 mm rounds and 357 caliber rounds. Type IIIA will stop 44 Magnum shots.
Type III includes hard armor plate designed to deflect 762 mm steel-jacketed rifle rounds. Type IV--the highest rated--deflects 30 caliber armor-piercing rifle bullets.
To qualify for any of NIJ's ratings, body armor must pass specific tests using bullets of specific types and velocities. Bullets used include Full Metal Jacket or FMJ rounds as well as soft-nosed, semi-jacketed and hollow-point rounds.
Body armor vests are not tested with all possible rounds. Vests that pass the standards for Level IIA will not withstand rifle fire or Teflon-coated handgun ammunition.
Level IIA does hold up to 9mm handgun fire at 1225 ft/sec, but not to the same caliber at 1305 ft/sec. Reconditioned armor passes at lower standards than does new armor.
Soft armor bulletproof vests do offer good protection against handgun rounds. Vests become lighter and less obvious as protection decreases.
Some brands offer better protection with less weight, as well as giving better body coverage. Light vests may save weight by reducing the area of the vest or leaving side gaps.
Ratings do not indicate the amount of protection--a rating only means that the weakest part of the vest provided the minimum ballistic resistance for that standard.
Tactical police units and military personnel requiring protection against high caliber rifle rounds wear heavier composite armor using both Kevlar fabric and ceramic armor plate. Though the Kevlar will resist small arms, the ceramic plating provides the defense against rifle fire.
Tactical gear can include protection for the groin and throat but the added weight and bulk limits mobility. The gear usually is camouflaged but not readily concealable.
Bulletproof vests can be designed to resist attacks beyond the usual test limits. Accessories offer passive defense against stabbing and blunt trauma as well as giving extra body area coverage.
Armor sets may be specially designed for high-risk work such as mine removal. Vests are even available for dogs.
Vests built to protect against common firearms may be more practical in ordinary circumstances than those constructed to resist exotic ammunition. Concealable soft bulletproof vests also do not cue aggressors to attack unprotected targets like the head rather than the chest.