List of body armor performance standards


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.

VPAM armor standard (International)

The VPAM scale as of 2009 runs from 1 to 14, with 1-5 being soft armor, and 6-14 being hard armor. Tested armor must withstand three hits, spaced apart, of the designated test threat with no more than of back-face deformation in order to pass. Of note is the inclusion of special regional threats such as Swiss P AP from RUAG and.357 DAG. According to VPAM's website, it is apparently used in France and Britain.
The VPAM scale is as follows:
Armor LevelProtection
PM 1
  • 2.6±0.1 g .22 Long Rifle lead round-nose bullets at a velocity of 360±10 m/s
PM 2
  • 8.0±0.1 g 9×19mm Parabellum DM41 FMJ round-nose lead-core bullets at a velocity of 360±10 m/s
  • PM 3
  • 8.0±0.1 g 9×19mm Parabellum DM41 FMJ round-nose lead-core bullets at a velocity of 415±10 m/s
  • PM 4
  • 10.2±0.1 g .357 Magnum bullets at a velocity of 430±10 m/s
  • 15.6±0.1 g .44 Magnum bullets at a velocity of 440±10 m/s
  • PM 5
  • 7.1±0.1 g .357 Magnum FMs bullets at a velocity of 580±10 m/s
  • PM 6
  • 8.0±0.1 g 7.62×39mm PS mild steel-core bullets at a velocity of 720±10 m/s
  • PM 7
  • 4.0±0.1 g 5.56×45mm SS109/US: M855 FMJ bullets at a velocity of 950±10 m/s
  • 9.55±0.1 g 7.62×51mm DM111 steel-core bullets at a velocity of 830±10 m/s
  • PM 8
  • 7.7±0.1 g 7.62×39mm BZ API bullets at a velocity of 740±10 m/s
  • PM 9
  • 9.7±0.2 g 7.62×51mm P80 armor-piercing bullets at a velocity of 820±10 m/s
  • PM 10
  • 10.4±0.1 g 7.62×54mmR B32 API bullets at a velocity of 860±10 m/s
  • PM 11
  • 8.4±0.1 g 7.62×51mm Nammo AP8/US M993 armor-piercing bullets at a velocity of 930±10 m/s
  • PM 12
  • 12.7±0.1 g 7.62×51mm RUAG SWISS P AP armor-piercing bullets at a velocity of 810±10 m/s
  • PM 13
  • 43.5±0.1 g 12.7×99mm RUAG SWISS P penetrator bullets at a velocity of 930±10 m/s
  • PM 14
  • 63.4±0.1 g 14.5×114mm B32 API bullets at a velocity of 911±10 m/s
  • TR armor standard (Germany)

    The Technische Richtlinie Ballistische Schutzwesten is a regulation guide in Germany for body armor. It is mainly issued for body armor used by the German police, but also for the German armed forces and civilian available body armor. Producers have to meet the criteria of the TR, if they want to participate in open competitive bidding made by German agencies. The TR specifies different Schutzklassen, which translates to protection classes, which a body armor can have. It specifies five different classes ranging from L to 4 of ballistic protection. It also gives specifications for additional Stichschutz, protection against knives, using the same classes as the ballistic protection, but giving it the additional ST label. The ballistic tests to determine a class are now integrated into the VPAM guidelines, so that the tests differ just in minor details and only one test is significantly different as of 2008.
    The TR scale is as follows:
    Armor LevelProtection
    SK L
    This armor would protect against three hits, fired from 5±0.5 meters, as well as point-blank shots, of:
    • 8.0±0.1 g 9×19mm Parabellum DM41 FMJ round-nose lead-core bullets at a velocity of 360±10 m/s
    SK 1This armor would protect against three hits, fired from 5±0.5 meters in an angle of 25°, as well as 3 shots at point-blank, of:
    • 8.0±0.1 g 9×19mm Parabellum DM41 FMJ round-nose lead-core bullets at a velocity of 415±10 m/s
    • 6.0±0.1 g 9×19mm Parabellum QD-PEP II/S police special round bullets at a velocity of 460±10 m/s
    • 6.1±0.1 g 9×19mm Parabellum Action 4 police special round bullets at a velocity of 460±10 m/s
    SK 2
  • 7.1±0.1 g .357 Magnum FMs bullets at a velocity of 580±10 m/s
  • SK 3
  • 4.0±0.1 g 5.56×45mm SS109/US: M855 FMJ bullets at a velocity of 950±10 m/s
  • 9.55±0.1 g 7.62×51mm DM111 steel-core bullets at a velocity of 830±10 m/s
  • SK 4
  • 9.7±0.2 g 7.62×51mm P80 armor-piercing bullets at a velocity of 820±10 m/s
  • The German TR are generally comparable to the American NIJ, but the German TR usually tests more threat scenarios, as there are no point-blank shots as well as no police special rounds. In contrast the NIJ tests for bigger calibers and higher man stopping power. And while the German TR tests smaller calibers and lighter bullets, it also tests more aggressive rounds, as the first test already uses steel FMJ bullets, while the NIJ uses normal FMJ rounds. In addition SK 4, the highest protection class, is specified to withstand three hits, while Level IV needs only to withstand one hit - although by a bigger caliber.

    HOSDB armor standard (United Kingdom)

    The Home Office Scientific Development Branch is governing standards and testing protocols for police body armor.
    Armor LevelProtection
    HG1/AThis armor would protect against six hits, fired from 5 meters, of:
    • 8.0±0.1 g 9×19mm Parabellum DM11 FMJ round-nose lead-core bullets at a velocity of 365±10 m/s
    • 10.2±0.1 g .357 Magnum R375M3 JSP bullets at a velocity of 390±10 m/s
    HG1This armor would protect against six hits, fired from 5 meters, of:
  • 8.0±0.1 g 9×19mm Parabellum DM11 FMJ round-nose lead-core bullets at a velocity of 365±10 m/s
  • 10.2±0.1 g .357 Magnum R375M3 JSP bullets at a velocity of 390±10 m/s
  • HG2This armor would protect against six hits, fired from 5 meters, of:
  • 8.0±0.1 g 9×19mm Parabellum DM11 FMJ round-nose lead-core bullets at a velocity of 390±10 m/s
  • 10.2±0.1 g .357 Magnum R375M3 JSP bullets at a velocity of 430±10 m/s
  • HG3This armor would protect against six hits, fired from 10 meters, of:
  • 4.0±0.1 g 5.56×45mm LE223T3 bullets at a velocity of 750±15 m/s
  • RF1This armor would protect against three hits, fired from 10 meters, of:
  • 9.3±0.1 g 7.62×51mm L2A2 FMJ bullets at a velocity of 830±15 m/s
  • RF2This armor would protect against three hits, fired from 10 meters, of:
  • 9.7±0.1 g 7.62×51mm L40A2 steel-core bullets at a velocity of 850±15 m/s
  • SG3This armor would protect against 1 hit, fired from 10 meters, of:
  • 28.4±0.1 g 12 gauge rifled lead slug at a velocity of 435±25 m/s
  • BFD to be measured after each shot, maximum allowed BFD for HG1/A class is and for the rest.

    GOST armor standard (Russia)

    R 50744-95 is the Russian Federation standard for body armor. Prior to the 2017 revision, the threat levels ran from 1 to 6. Noticeably, it included threats with the suffix A, which denote heightened ratings as opposed to lowered ratings in the NIJ standard.
    The old standards are as follows:
    Armor LevelProtection
    Class 1
    • 5.9 g 9×18mm Makarov 57-N-181S steel-core bullets at a velocity of 305–325 m/s
    • 6.8 g 7.62×38mmR 57-N-122 lead core bullets at a velocity of 275–295 m/s.
    Class 2
  • 2.5 g 5.45×18mm steel-core MPC 7N7 bullets at a velocity of 310–335 m/s
  • 5.5 g 7.62×25mm Tokarev steel-core bullets at a velocity of 415–445 m/s
  • Class 2A
  • 35 g 12 gauge lead-core "Hunter" shotshells at a velocity of 390–410 m/s
  • Class 3
  • 3.4 g 5.45×39mm 7N6 hardened steel-core bullets at a velocity of 890–910 m/s
  • 7.9 g 7.62×39mm 57-N-231 hardened steel-core bullets at a velocity of 710–740 m/s
  • Class 4
  • 3.4 g 5.45×39mm 7N10 hardened steel-core bullets at a velocity of 890–910 m/s
  • Class 5
  • 9.6 g 7.62×54mmR 57-N-323S steel-core bullets at a velocity of 820–840 m/s
  • 7.9 g 7.62×39mm 57-N-231 hardened steel-core bullets at a velocity of 710–740 m/s
  • Class 5A
  • 7.4 g 7.62×39mm 57-BZ-231 armor-piercing incendiary bullets at a velocity of 720–750 m/s.
  • Class 6
  • 9.6 g 7.62×54mmR ST-M2 hardened steel-core bullets at a velocity of 820–840 m/s
  • Class 6A
  • 10.4 g 7.62×54mmR 7-BZ-3 armor-piercing incendiary bullets at a velocity of 800–835 m/s
  • With the 2017 revision, the standards have changed significantly. Threat classes now range from BR1 to BR6. 'A'-suffixed classes have been eliminated, and their test threats have been either merged into the new categories, such as Classes 6 and 6A being moved into Class BR5, or removed entirely, as in the case of Class 2A. Additionally, several of the threat levels have been increased in difficulty with the introduction of new test threats; most notably is the introduction of Class BR6, which requires the tested armor to survive three hits of 12.7×108mm B32 API. In spite of the more difficult test threats, the back-face deformation limit remains unchanged.
    The updated standards from the 2017 revision are as follows:
    Armor LevelProtection
    BR1
    BR2
  • 7.93 g 9×21mm Gyurza 7N28 lead-core bullets from an SR-1 Vektor at a velocity of 390±10 m/s
  • BR3
  • 5.2 g 9×19mm Parabellum 7N21 hardened steel-core bullets from an MP-443 Grach at a velocity of 455±10 m/s
  • BR4
  • 3.4 g 5.45×39mm 7N10 hardened steel-core bullets from an AK-74 at a velocity of 895±15 m/s
  • 7.9 g 7.62×39mm 57-N-231 hardened steel-core bullets from an AKM at a velocity of 720±15 m/s
  • BR5
  • 9.4 g 7.62×54mmR 7N13 hardened steel-core bullets from a SVD sniper rifle at a velocity of 830±15 m/s
  • 7.9 g 7.62×54mmR 7BZ3 API bullets from a SVD sniper rifle at a velocity of 810±15 m/s
  • BR6
  • 48.2 g 12.7×108mm 57-BZ-542 API bullets from an OSV-96 sniper rifle at a velocity of 830±20 m/s.
  • NIJ armor standard (United States)

    Ballistic resistance (before April 2024)

    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 :
    Armor LevelProtection
    Level I
    It is no longer part of the standard.
    Level IIA
    • 8 g 9×19mm Parabellum Full Metal Jacketed Round Nose bullets at a velocity of 373 m/s ± 9.1 m/s
    • 11.7 g .40 S&W Full Metal Jacketed bullets at a velocity of 352 m/s ± 9.1 m/s
    • 14.9 g .45 ACP Full Metal Jacketed bullets at a velocity of 275 m/s ± 9.1 m/s.
    Conditioned armor protects against
    • 8 g 9 mm FMJ RN bullets at a velocity of 355 m/s ± 9.1 m/s
    • 11.7 g .40 S&W FMJ bullets at a velocity of 325 m/s ± 9.1 m/s
    • 14.9 g .45 ACP Full Metal Jacketed bullets at a velocity of 259 m/s ± 9.1 m/s.
    It also provides protection against the threats mentioned in .
    Level II
    • 8 g 9 mm FMJ RN bullets at a velocity of 398 m/s ± 9.1 m/s
    • 10.2 g .357 Magnum Jacketed Soft Point bullets at a velocity of 436 m/s ± 9.1 m/s.
    Conditioned armor protects against
    • 8 g 9 mm FMJ RN bullets at a velocity of 379 m/s ±9.1 m/s
    • 10.2 g .357 Magnum Jacketed Soft Point bullets at a velocity of 408 m/s ±9.1 m/s.
    It also provides protection against the threats mentioned in .
    Level IIIA
    • 8.1 g .357 SIG FMJ Flat Nose bullets at a velocity of 448 m/s ± 9.1 m/s
    • 15.6 g .44 Magnum Semi Jacketed Hollow Point bullets at a velocity of 436 m/s.
    Conditioned armor protects against
    • 8.1 g .357 SIG FMJ Flat Nose bullets at a velocity of 430 m/s ± 9.1 m/s
    • 15.6 g .44 Magnum Semi Jacketed Hollow Point bullets at a velocity of 408 m/s ± 9.1 m/s.
    It also provides protection against most handgun threats, as well as the threats mentioned in .
    Level III
    It also provides protection against the threats mentioned in .
    Level IV
    It also provides at least single hit protection against the threats mentioned in .

    "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+" 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:
    Armor LevelProtection
    NIJ HG1
    This is roughly equivalent to the obsolete NIJ Level II ballistic protection level.
    NIJ HG2
    This is roughly equivalent to the obsolete NIJ Level IIIA ballistic protection level.
    NIJ RF1
    This is roughly equivalent to the obsolete NIJ Level III ballistic protection level. 7.62x51mm and 5.56x45mm projectiles may be up to lighter than values given.
    NIJ RF2
    This is identical to the ballistic protection provided by NIJ RF1, with the addition of 5.56x45mm M855. This level has no equivalent in obsolete NIJ Standard-0101.06.
    NIJ RF3
    This is roughly equivalent to the obsolete NIJ Level IV ballistic protection level. Projectile may be up to lighter than value given.

    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". 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, while unconditioned Level IIIA would have been shot at. 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. 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 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. The overtest condition for this level is 36±0.60 J.
    • 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. The overtest condition for this level is 50±0.70 J.
    • 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. The overtest condition for this level is 65±0.80 J.
    For all three levels, the maximum blade or spike penetration allowed is 7 mm, 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.
    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.

    US military armor standards

    Although the US military requirements for body armor mirror the NIJ's on a surface level, the two are very different systems. The two systems share a limit on back-face deformation, but SAPI-series plates increase linearly in protection, and require a soft armor backer in order to reach their stated level of protection.
    Armor Type:Protection:
    Soft Armor
    • RCC at a velocity of when dry and when wet.
    • RCC at a velocity of when dry and when wet.
    • RCC at a velocity of when dry and when wet.
    • RCC at a velocity of when dry and when wet.
    • RCC at a velocity of after hot and cold temperature exposure and accelerated aging.
    • RCC at a velocity of after contamination with motor oil and JP-8.
    • Fragment Simulating Projectile at a velocity of when dry.
    • 9×19mm Remington FMJ at a velocity of + and .
    SAPI
  • 3 shots of 7.62×51mm M80 ball bullets at a velocity of +.
  • 3 shots of 7.62×54mmR LPS steel-core FMJ bullets at a velocity of +.
  • 3 shots of 5.56×45mm M855 bullets at a velocity of +.
  • ISAPI
  • 3 shots of 7.62×51mm M80 ball bullets at a velocity of +.
  • 3 shots of 7.62×54mmR LPS steel-core FMJ bullets at a velocity of +.
  • 3 shots of 5.56×45mm M855 bullets at a velocity of +.
  • 3 shots of 7.62×39mm 57-BZ-231 armor-piercing incendiary bullets at a velocity of +.
  • ESAPI
  • 3 shots of 7.62×51mm M80 ball bullets at a velocity of +.
  • 3 shots of 7.62×54mmR LPS steel-core FMJ bullets at a velocity of +.
  • 3 shots of 5.56×45mm M855 bullets at a velocity of +.
  • 2 shots of [.30-06 Springfield#United States|.30-06 M2 AP] armor-piercing bullets at a velocity of +.
  • ESAPI
  • 3 shots of 7.62×51mm M80 ball bullets at a velocity of + and .
  • 3 shots of 7.62×54mmR LPS steel-core FMJ bullets at a velocity of + and .
  • 3 shots of 5.56×45mm M855 bullets at a velocity of + and .
  • 3 shots of .30-06 M2 AP armor-piercing bullets at a velocity of +.
  • 3 shots of 7.62×54mmR 7N1 "Sniper" steel-core bullets at a velocity of +.
  • 3 shots of 5.56×45mm M995 AP bullets at a velocity of +.
  • ESAPI
  • 3 shots of 7.62×54mmR LPS steel-core FMJ bullets at a velocity of + and .
  • 3 shots of .30-06 M2 AP armor-piercing bullets at a velocity of + and .
  • 3 shots of 7.62×54mmR 7N1 "Sniper" steel-core bullets at a velocity of +.
  • 3 shots of 5.56×45mm M995 AP bullets at a velocity of +.
  • XSAPIArmor is tested using a standard set of test methods under ARMY MIL-STD-662F and STANAG 2920 Ed2. The Department of Defense armor programs-of-record procure armor using these test standards. In addition, special requirements can be defined under this process such as flexible rifle protection, fragment protection for the extremities, etc.

    GA141 armor standard (China)

    The Chinese Ministry of Public Security has maintained GA141, a standard document for describing the ballistic resistance of police armor, since 1996., the latest revision is GA141-2010. The standard defines the following grades using domestic weapons:
    Armor LevelProtection
    GA 1
    Levels higher than 6 are marked "special". Levels 1 through 5 are to be tested with 6 shots. Level 6 is to be tested with 2 shots.
    Annex A describes the use of GA grades against other "common" threats. 9×18mm Makarov is assigned to GA 1, 9×19mm to GA 2, 9×19mm AP and 5.8×21mm DAP92 AP to GA 4, 5.8×42mm DBP87 to GA 6, and "type 53" 7.62×54mmR API to "special grade".

    Ballistic testing V50 and V0

    Measuring the ballistic performance of armor is based on determining the kinetic energy of a bullet at impact. Because the energy of a bullet is a key factor in its penetrating capacity, velocity is used as the primary independent variable in ballistic testing. For most users the key measurement is the velocity at which no bullets will penetrate the armor. Measuring this zero penetration velocity must take into account variability in armor performance and test variability. Ballistic testing has a number of sources of variability: the armor, test backing materials, bullet, casing, powder, primer and the gun barrel, to name a few.
    Variability reduces the predictive power of a determination of V0. If for example, the v0 of an armor design is measured to be with a 9 mm FMJ bullet based on 30 shots, the test is only an estimate of the real v0 of this armor. The problem is variability. If the v0 is tested again with a second group of 30 shots on the same vest design, the result will not be identical.
    Only a single low velocity penetrating shot is required to reduce the v0 value. The more shots made the lower the v0 will go. In terms of statistics, the zero penetration velocity is the tail end of the distribution curve. If the variability is known and the standard deviation can be calculated, one can rigorously set the V0 at a confidence interval. Test Standards now define how many shots must be used to estimate a v0 for the armor certification. This procedure defines a confidence interval of an estimate of v0.
    v0 is difficult to measure, so a second concept has been developed in ballistic testing called the ballistic limit. This is the velocity at which 50 percent of the shots go through and 50 percent are stopped by the armor. US military standard MIL-STD-662F V50 Ballistic Test define a commonly used procedure for this measurement. The goal is to get three shots that penetrate that are slower than a second faster group of three shots that are stopped by the armor. These three high stops and three low penetrations can then be used to calculate a v50 velocity.
    In practice this measurement of v50 requires 1–2 vest panels and 10–20 shots. A very useful concept in armor testing is the offset velocity between the v0 and v50. If this offset has been measured for an armor design, then v50 data can be used to measure and estimate changes in v0. For vest manufacturing, field evaluation and life testing both v0 and v50 are used. However, as a result of the simplicity of making v50 measurements, this method is more important for control of armor after certification.

    Military testing: fragment ballistics

    After the Vietnam War, military planners developed a concept of "Casualty Reduction". The large body of casualty data made clear that in a combat situation, fragments, not bullets, were the most important threat to soldiers. After WWII, vests were being developed and fragment testing was in its early stages. Artillery shells, mortar shells, aerial bombs, grenades, and antipersonnel mines are all fragmentation devices. They all contain a steel casing that is designed to burst into small steel fragments or shrapnel, when their explosive core detonates. After considerable effort measuring fragment size distribution from various NATO and Soviet bloc munitions, a fragment test was developed. Fragment simulators were designed, and the most common shape is a right circular cylinder or RCC simulator. This shape has a length equal to its diameter. These RCC Fragment Simulation Projectiles are tested as a group. The test series most often includes 2 grain, 4 grain, 16 grain, and 64 grain mass RCC FSP testing. The 2-4-16-64 series is based on the measured fragment size distributions.
    The second part of "Casualty Reduction" strategy is a study of velocity distributions of fragments from munitions. Warhead explosives have blast speeds of to. As a result, they are capable of ejecting fragments at very high speeds of over, implying very high energy. The military engineering data showed that, like the fragment size, the fragment velocities had characteristic distributions. It is possible to segment the fragment output from a warhead into velocity groups. For example, 95% of all fragments from a bomb blast under have a velocity of or less. This established a set of goals for military ballistic vest design.
    The random nature of fragmentation required the military vest specification to trade off mass vs. ballistic-benefit. Hard vehicle armor is capable of stopping all fragments, but military personnel can only carry a limited amount of gear and equipment, so the weight of the vest is a limiting factor in vest fragment protection. The 2-4-16-64 grain series at limited velocity can be stopped by an all-textile vest of approximately 5.4 kg/m2. In contrast to the design of vest for deformable lead bullets, fragments do not change shape; they are steel and can not be deformed by textile materials. The FSP is about the size of a grain of rice; such small fast moving fragments can potentially slip through the vest, moving between yarns. As a result, fabrics optimized for fragment protection are tightly woven, although these fabrics are not as effective at stopping lead bullets.

    Backing materials for testing

    Ballistic

    One of the critical requirements in soft ballistic testing is measurement of "back side signature" in a deformable backing material placed behind the targeted vest. The majority of military and law enforcement standards have settled on an oil/clay mixture for the backing material, known as Roma Plastilena. Although harder and less deformable than human tissue, Roma represents a "worst case" backing material when plastic deformations in the oil/clay are low. The oil/clay mixture of "Roma" is roughly twice the density of human tissue and therefore does not match its specific gravity, however "Roma" is a plastic material that will not recover its shape elastically, which is important for accurately measuring potential trauma through back side signature.
    The selection of test backing is significant because in flexible armor, the body tissue of a wearer plays an integral part in absorbing the high energy impact of ballistic and stab events. However the human torso has a very complex mechanical behavior. Away from the rib cage and spine, the soft tissue behavior is soft and compliant. In the tissue over the sternum bone region, the compliance of the torso is significantly lower. This complexity requires very elaborate bio-morphic backing material systems for accurate ballistic and stab armor testing. A number of materials have been used to simulate human tissue in addition to Roma. In all cases, these materials are placed behind the armor during test impacts and are designed to simulate various aspects of human tissue impact behavior.
    One important factor in test backing for armor is its hardness. Armor is more easily penetrated in testing when backed by harder materials, and therefore harder materials, such as Roma clay, represent more conservative test methods.
    Backer typeMaterialsElastic/plasticTest typeSpecific gravityRelative hardness vs gelatinApplication
    Roma Plastilina Clay #1Oil/Clay mixturePlasticBallistic and Stab>2Moderately hardBack face signature measurement. Used for most standard testing
    10% gelatinAnimal protein gelVisco-elasticBallistic~1 Softer than baselineGood simulant for human tissue, hard to use, expensive. Required for FBI test methods
    20% gelatinAnimal protein gelVisco-elasticBallistic~1 BaselineGood simulant for skeletal muscle. Provides dynamic view of event.
    HOSDB-NIJ FoamNeoprene foam, EVA foam, sheet rubberElasticStab~1Slightly harder than gelatinModerate agreement with tissue, easy to use, low in cost. Used in stab testing
    Silicone gelLong chain silicone polymerVisco-elasticBiomedical~1.2Similar to gelatinBiomedical testing for blunt force testing, very good tissue match
    Pig or Sheep animal testingLive tissueVariousResearch~1Real tissue is variableVery complex, requires ethical review for approval

    Stab

    Stab and spike armor standards have been developed using 3 different backing materials. The Draft EU norm calls out Roma clay, The California DOC called out 60% ballistic gelatin and the current standard for NIJ and HOSDB calls out a multi-part foam and rubber backing material.
    • Using Roma clay backing, only metallic stab solutions met the 109 joule Calif. DOC ice pick requirement
    • Using 10% Gelatin backing, all fabric stab solutions were able to meet the 109 joule Calif. DOC ice pick requirement.
    • Most recently the Draft ISO prEN ISO 14876 norm selected Roma as the backing for both ballistics and stab testing.
    This history helps explain an important factor in Ballistics and Stab armor testing, backing stiffness affects armor penetration resistance. The energy dissipation of the armor-tissue system is Energy = Force × Displacement when testing on backings that are softer and more deformable the total impact energy is absorbed at lower force. When the force is reduced by a softer more compliant backing the armor is less likely to be penetrated. The use of harder Roma materials in the ISO draft norm makes this the most rigorous of the stab standards in use today.