What it is
STANAG 4820 is the NATO Standardization Agreement covering the technical performance specification for the interchangeability of 4.6 mm x 30 ammunition. This is Edition 1, promulgated 4 December 2020, and the document states plainly that "This STANAG does not supersede any document."
A STANAG is not the specification
A STANAG is the agreement by which NATO nations commit to implement a standard, not the technical specification itself. STANAG 4820's own text is short and administrative: an aim, one interoperability requirement, and the ratification, reporting and review machinery. The 4.6 mm x 30 ammunition characteristics named in its title are specified in a separate publication, AOP-4820 Edition A, which the STANAG names as the standard participating nations agree to implement. Anyone actually designing, specifying or testing those characteristics needs AOP-4820's own text, and AEP-97 for how ammunition is proven against it, not this cover agreement.
What it commits nations to
The stated aim is "to respond to the following interoperability requirements", and the interoperability requirement itself is that "the NATO nations agree to comply with the standardization drawings and technical specifications in AOP-4820". Participating nations "agree to implement the following standard", named as AOP-4820, Edition A.
Who it binds, and how
STANAG 4820 binds nations, not suppliers. It is effective "upon receipt and ready to be used by the implementing nations and NATO bodies", while partner nations are only "invited to adopt this STANAG" rather than bound by ratification. Implementation is a further, distinct step: the STANAG "will be considered to have been implemented when ratifying nations have introduced into their armed forces ammunition which has met the requirements of this STANAG in AOP-4820 and the Multi-Calibre Manual of Proof and Inspection Procedures (AEP-97)". A shortcut is explicitly ruled out: "reference to the STANAG alone as the National Implementing Document does not meet this intent" - a nation has to hold documentation demonstrating the ammunition actually met the requirements, identified as its National Implementing Document. A supplier meets STANAG 4820, or the AOP-4820 characteristics it covers, only where a contract or tender says so; the document sets no obligation reaching a supplier directly, and no compliance date of its own.
How it's evaluated
STANAG 4820 describes no certification scheme and no audit. What it describes is nations reporting to NATO: national decisions on ratification and implementation are provided to the NATO Standardization Office, and "the national responses are recorded in the NATO Standardization Document Database (NSDD)". Nobody is "STANAG 4820 certified", and the document never uses that language. Where an ammunition design is actually tested for interchangeability, that proof and inspection work runs under AEP-97 and AOP-4820, not this cover agreement.
Standards it references
STANAG 4820 covers AOP-4820, the publication that carries the ammunition's own performance requirements. Its related-documents list also names STANAG 2953 (Identification of Ammunition) together with AOP-02, AAP-06 (the NATO Glossary of Terms and Definitions), and STANAG 4823 (the Multi-Calibre Manual of Proof and Inspection for NATO small arms ammunition) together with AEP-97. Reviews of STANAG 4820 itself, and national reporting on ratification, implementation and adoption, run under AAP-03.