The National Institute of Justice (NIJ) is the U.S. government agency responsible for setting performance standards for body armor worn by law enforcement officers. The NIJ’s ballistic rating system classifies body armor by the types and levels of bullet resistance provided.
Below are the main ballistic ratings defined by the NIJ:
- **NIJ Level IIA**:
- Protection from: 9mm full metal jacketed round nose (FMJ RN) bullets with a specified mass of 8.0 g (124 gr) impacting at a velocity of 373 m/s (1,225 ft/s) or less, and .40 S&W FMJ bullets with a specified mass of 11.7 g (180 gr) impacting at a velocity of 352 m/s (1,155 ft/s) or less.
- Additional protection from lower velocity 9mm and .40 S&W ammunition.
- **NIJ Level II**:
- Protection from: 9mm FMJ RN bullets with a specified mass of 8.0 g (124 gr) impacting at a velocity of 398 m/s (1,305 ft/s) or less, and .357 Magnum jacketed soft point (JSP) bullets with a specified mass of 10.2 g (158 gr) impacting at a velocity of 436 m/s (1,430 ft/s) or less.
- Offers protection against the threats included in Level IIA.
- **NIJ Level IIIA**:
- Protection from: .357 SIG FMJ flat nose (FN) bullets with a specified mass of 8.1 g (125 gr) impacting at a velocity of 448 m/s (1,470 ft/s) or less, and .44 Magnum semi-jacketed hollow point (SJHP) bullets with a specified mass of 15.6 g (240 gr) impacting at a velocity of 436 m/s (1,430 ft/s) or less.
- Offers protection against most handgun threats and the threats included in Levels IIA and II.
- **NIJ Level III**:
- Protection from: 7.62mm FMJ steel jacketed bullets (U.S. military designation M80) with a specified mass of 9.6 g (147 gr) and impacting at a velocity of 847 m/s (2,780 ft/s) or less.
- Typically requires hard armor plates made of materials like steel, ceramic, or polyethylene.
- Protects against all threats included in Levels IIA, II, and IIIA, plus high-velocity rifle rounds.
- **NIJ Level IV**:
- Protection from: .30 caliber armor-piercing (AP) bullets (U.S. military designation M2 AP) with a specified mass of 10.8 g (166 gr) and impacting at a velocity of 878 m/s (2,880 ft/s) or less.
- Typically requires hard armor plates made of ceramic or other composite materials.
- Protects against all threats included in Levels IIA, II, IIIA, and III, plus armor-piercing rifle rounds.
It’s important to note that while an armor level might protect against its specified threats, it might not necessarily protect against all potential threats. Furthermore, “blunt trauma” or the injury potential from the impact force of a bullet (even if it doesn’t penetrate the armor) is also an essential concern, and the NIJ standards take this into consideration when testing body armor.
