The Spartan Armor Systems AR550 Steel Body Armor Plate delivers Special Threat Rated Level III+/RF2 rifle protection, manufactured entirely in the USA from American AR550 ballistic-grade steel. The AR550 carries a special threat rating to stop rounds up to 5.56x45 M855 Green Tip, and the Single Curve Full Coat variant is NIJ Listed under NIJ 0101.06 Level III. Two coating options — Base Coat for corrosion protection and Full Coat Encapsaloc — address different user priorities. Available in 10x12 and 11x14 in Shooters Cut, and 10x12 in High Mobility Cut, with Single Curve and Advanced Triple Curve (ATC) geometries.

Who this is for

• Law enforcement officers: who need rifle-rated front and back protection in a duty plate carrier at a price that allows two-plate loadouts without budget strain.
• Responsible civilians: building a home-defense or range-ready armor system who want domestic manufacture and documented special threat performance against common rifle calibers including M855.
• Military and security personnel: seeking a cost-effective steel plate backup or training plate that meets NIJ 0101.06 Level III listing requirements in the Single Curve Full Coat configuration.

Ballistic performance

AR550 steel is a harder alloy grade than the more common AR500, and that additional hardness translates directly into a higher certified threat ceiling. The AR550 plate is rated to stop 7.62x51mm M80 Ball — the NATO full-power rifle round — which satisfies NIJ 0101.06 Level III requirements. Beyond that baseline, the AR550 carries a Special Threat Rating of Level III+/RF2, confirming independent testing against 5.56x45 M855 Green Tip (penetrator round) at standard velocity.

Two coating configurations are available. The Base Coat provides corrosion protection for the steel core and keeps weight and thickness at the bare-steel minimum. The Full Coat option applies Encapsaloc, a proprietary coating that significantly reduces fragmentation and spall risks — the byproduct steel fragments that are the primary secondary hazard of any steel armor strike. For any deployment where a round may actually impact the plate, the Full Coat option is the operationally appropriate choice. The Single Curve Full Coat variant is NIJ Listed under NIJ 0101.06 Level III.

Plate compatibility and cut geometry

The AR550 is available in Shooters Cut and High Mobility Cut. The Shooters Cut (10x12 and 11x14) offers maximum frontal coverage and fits the majority of plate carriers designed around standard 10x12 or 11x14 pockets. The High Mobility Cut (10x12 only) removes material from the upper shoulder corners, reducing weight by roughly 1.4 lbs per plate compared to the Shooters Cut equivalent, and increasing shoulder and arm range of motion — the trade-off is reduced upper-chest coverage.

Both cuts are available in Single Curve and Advanced Triple Curve (ATC). Single Curve plates have a straightforward front-to-back bend that seats correctly in most flat or single-curve plate pockets. The Advanced Triple Curve geometry adds a vertical contour that conforms more closely to the torso, improving both comfort during prolonged wear and stability under a carrier. Specifications for Single Curve and ATC variants are identical within each size and coating option. Contact us if you need fitment confirmation for a specific carrier model.

Specifications

Fit and carrier compatibility

The 10x12 and 11x14 Shooters Cut dimensions are the two most common plate pocket sizes in production plate carriers. Any carrier with a 10x12 or 11x14 plate pocket — single-curve or flat — will accept these plates in the Single Curve variant. The ATC geometry seats best in carriers with a formed or single-curve pocket; avoid forcing an ATC plate into a flat rigid pocket. The High Mobility Cut 10x12 fits the same 10x12 pockets as the Shooters Cut variant, with extra clearance at the shoulder corners. Soft armor backers can be used behind these plates in carriers that include a backer sleeve. Contact us for carrier-specific fitment questions.

Frequently asked questions

What rounds does the AR550 stop?

The AR550 is rated to stop 7.62x51mm M80 Ball at Level III threat parameters, and carries a Special Threat Rating of Level III+/RF2 to stop 5.56x45 M855 Green Tip. This covers the majority of common rifle threats. It does not carry a Level IV rating and is not rated against hard armor-piercing rounds such as 30 caliber M2 AP.

What is the difference between Base Coat and Full Coat?

Base Coat applies corrosion protection only, keeping the plate at minimum weight and 0.25 in thickness. Full Coat applies Encapsaloc, a proprietary coating that significantly reduces spall and fragmentation — the steel fragments ejected rearward when a round strikes the plate. For active-use armor systems, Full Coat is the operationally recommended choice. The Full Coat variant also qualifies for NIJ Listing under 0101.06 Level III in Single Curve configuration.

What is the difference between Single Curve and Advanced Triple Curve (ATC)?

Single Curve plates have one bend running horizontally across the plate face, matching the basic contour of most carrier pockets. Advanced Triple Curve adds a second and third contour axis — essentially a more body-shaped bend — that improves both torso contact and comfort during extended wear. Ballistic specifications are identical between the two geometries for the same size and coating.

What is the difference between Shooters Cut and High Mobility Cut?

Shooters Cut provides full rectangular coverage with standard shoulder corners. High Mobility Cut removes material from both upper corners, reducing weight by roughly 1.4 lbs per plate on the 10x12 and increasing shoulder mobility. The trade-off is reduced coverage of the upper chest and clavicle zone. High Mobility Cut is available in 10x12 only.

Does this plate need a soft armor backer?

Steel plates do not require a soft armor backer to function. However, pairing a Level IIIA soft backer behind the steel plate provides added trauma reduction and can help manage any residual spall not captured by the Encapsaloc coating. Whether a backer is needed depends on the threat environment and the carrier's available depth.

Can this plate be shipped to my state?

This plate cannot be shipped to New York or Connecticut due to state body armor restrictions. All orders are subject to US export regulations. Under 18 U.S.C. § 931, any person with a federal felony conviction for a crime of violence is prohibited from purchasing or possessing body armor.