thumb|[[Interceptor Body Armor vest with corresponding SAPI plate.]]
The Small Arms Protective Insert (SAPI) is a ceramic ballistic plate used by the United States Armed Forces. It was first used in the Ranger Body Armor and Interceptor Body Armor; both are ballistic vests. It is now also used in the Improved Outer Tactical Vest as well as the Modular Tactical Vest, in addition to commercially available "plate carriers". The Kevlar Interceptor vest itself is designed to stop projectiles up to and including 9×19mm Parabellum submachine gun rounds, in addition to fragmentation. To protect against higher-velocity rifle rounds, SAPI plates are needed.
ESAPI
thumb|ESAPI and ESBI plates are visible with the components of a [[Modular Tactical Vest in 2008.]]
thumb|Current-issue ESAPI and ESBI plates in 2021.
In May 2005, the U.S. Armed Forces began replacing the standard Small Arms Protective Insert plates with the Enhanced Small Arms Protective Insert (ESAPI).
An ESAPI provides protection from .30-06 Springfield M2 armor-piercing (AP) with a steel penetrator in accordance with the NIJ Level IV standard, but costs about $600 per plate, 50% more than SAPI plates. Newer revisions are also produced by CW Security Solutions, CW Armor, Point Blank Enterprises and Leading Technology Composites.
XSAPI
A call for a next generation plate, to stop even greater velocity threats than the ESAPI plate was issued by the U.S. Army in 2008. XSAPI did in fact offer slightly better protection, at the cost of more weight and thicker armor profile.
The XSAPI is intended to protect against an "X-Threat", which is able to be inferred from another source to be the M993 7.62 NATO armor piercing tungsten carbide projectile. In addition, there is record of the FBI utilizing the plate in May 2011.
The plates were developed in response to a perceived threat of AP projectiles in Iraq and Afghanistan. Over 120,000 inserts were procured; however, the AP threats they were meant to stop never materialized, and the plates were put into storage.
Materials and capabilities
The standard plate for the Interceptor body armor is made of boron carbide or silicon carbide ceramic.
Front and back SAPI plates:
- Extra Small - |
- Small - |
- Medium - |
- Large - |
- Extra Large |
ESAPI plates are the same size but greater in weight. The Enhanced S‐SAPIs have only size as the S-SAPIs. ESBI or Enhanced S-SAPI plates can be replaced with size X-Small ESAPI plates (by unfolding an extension built into the bottom of the ESBI Carrier assembly for the U.S. Army and the S-SAPI Carrier assembly for U.S. Marines for OTVs), if permitted by the unit commander.
ESBI plates:
- Small - 0.75 kg (1.65 lb) | 152 x 152 mm (6 x 6 in)
- Medium - 1 kg (2.19 lb) | 152 x 203 mm (6 x 8 in)
- Large - 1.15 kg (2.53 lb) | 178 x 203 mm (7 x 8 in)
Physics
The mechanism of effect lies in absorbing and dissipating the projectile's kinetic energy in local shattering of the ceramic plate and blunting the bullet material on the hard ceramic. The Spectra backing then spreads the energy of the impact to a larger area and stops the fragments as well as catching the, now deformed, projectile with its larger surface area. The same principle is used for the ceramic tiles used for the armored cockpits of some military airplanes, ceramic composites in ground vehicles, and the anti-spallation liners used in modern armored personnel carriers.
While the projectile may be stopped by the armor, there are cases of those who have been severely injured or killed by back face deformation. Though this is exceptionally rare in the field and in real combat cases, or at least rarely reported, as often in cases of injuries stemming from Behind Armor Blunt Trauma the sources has been found to either be rounds that already exceed or at least very nearly penetrate the Body Armor in question.
See also
- Ceramic plate
- Tactical Vest Antenna System
- Ceramic armor
- Bulletproof vest
- List of body armor performance standards