Do You Know about The NIJ Bulletproof Rating?

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        Body armor performance standards are lists generated by national authorities, of requirements for armor to perform reliably, clearly indicating what the armor may and may not defeat. Different countries have different standards, which may include threats that are not present in other countries.

Ballistic resistance (before April 2024)

NIJ Standard-0101.06 had specific performance standards for bullet resistant vests used by law enforcement. This rated vests on the following scale against penetration and also blunt trauma protection (deformation):

        "Special Threats" were ratings of armor which provide protection against specific projectiles. For example, the NIJ guidelines did not have any specification for armor that can stop M855 armor piercing ammunition. As a result, some manufacturers designated specific armors as "Level III+" (a designation not recognized by the NIJ) to specify armor which had up to level III protection and could protect against special threats like the M855, but did not provide level IV protection.

Ballistic resistance (after April 2024)

        In April 2024, NIJ began testing with NIJ Standard-0101.07 in conjunction with NIJ Standard-0123.00. NIJ Standard-0101.07 outlines testing procedures, while NIJ Standard-0123.00 describes ballistic protection levels. These standards completely replaced the NIJ Standard-0101.06. HG is rated for handgun threats and RF is rated for rifle threats.

The ballistic protection levels outlined in NIJ Standard 0123.00 are as follows:

        NIJ standards are used for law enforcement armors. Armor used by the United States military is not required to be tested under NIJ standards. Textile armor is tested for both penetration resistance by bullets and for the impact energy transmitted to the wearer.

Backface deformation

        Backface deformation is defined in NIJ Standard-0101.07 as "the indentation in the backing material caused by a projectile impact on the test item during testing".[10] It is measured by shooting armor mounted in front of a backing material, typically oil-based modeling clay. The clay is used at a controlled temperature and verified for impact flow before testing. After the armor is impacted with the test bullet, the vest is removed from the clay and the depth of the indentation in the clay is measured.

Conditioned armor

        Some armor tested under NIJ Standard-0101.07 is conditioned before testing, meaning it has been subjected to stress factors such as submersion, vibration, or impacts. These stress factors have been shown in some cases to degrade the performance of some armor material. The test-round velocity for conditioned armor is the same as that for unconditioned armor during testing, whereas in the previous standard the velocities would have varied. For example, under NIJ Standard-0101.06, conditioned Level IIIA would have been shot with a .44 Magnum round at 408 m/s (1,340 ft/s), while unconditioned Level IIIA would have been shot at 436 m/s (1,430 ft/s). Under NIJ Standard-0101.07, the velocity used for testing conditioned and unconditioned armor is the same. Armor conditioning procedures are outlined in ASTM E3078 Standard Practice for Conditioning of Hard Armor Test Items.

        Generally, textile armor material temporarily degrades when wet.[citation needed] As a result of this, the major test standards call for wet testing of textile armor. Mechanisms for this loss of performance are not known. Neutral water at room temp has not been shown in testing to negatively affect the performance of para-aramid or UHMWPE but acidic, basic and some other solutions can permanently reduce para-aramid fiber tensile strength.

        From 2003 to 2005, a large study of the environmental degradation of Zylon armor was undertaken by the US-NIJ. This concluded that water, long-term use, and temperature exposure significantly affect tensile strength and the ballistic performance of PBO or Zylon fiber. This NIJ study on vests returned from the field demonstrated that environmental effects on Zylon resulted in ballistic failures under standard test conditions.

Stab resistance

        The NIJ's stab resistance standards (Standard–0115.00) define three levels of protection:

        Level 1 armor is low-level protection suitable for extended wear and is usually covert. This armor protects against stab threats with a strike energy of 24±0.50 J (17.7±0.36 ft·lbf). The overtest condition for this level is 36±0.60 J (26.6±0.44 ft·lbf).

        Level 2 armor is medium-level protection suitable for extended wear and may be either overt or covert. This armor protects against stab threats with a strike energy of 33±0.60 J (24.3±0.44 ft·lbf). The overtest condition for this level is 50±0.70 J (36.9±0.51 ft·lbf).

        Level 3 is high-level protection suitable for wear in high risk situations and is usually overt. This armor protects against stab threats with a strike energy of 43±0.60 J (31.7±0.44 ft·lbf). The overtest condition for this level is 65±0.80 J (47.9±0.59 ft·lbf).

        For all three levels, the maximum blade or spike penetration allowed is 7 mm (0.28 in), with this limit being determined through research indicating that internal injuries to organs would be extremely unlikely at this depth of penetration. The overtest condition, which is intended to ensure an adequate margin of safety in the armor design, permits a maximum blade or spike penetration of 20 mm (0.79 in).

        The standard does not directly address slash resistance and instead notes that, since stab threats are more difficult to defeat, any armor that can defeat a stab threat will also defeat a slash threat.