I think you're thinking of IIIA, which is only rated to stop pistol/shotgun calibers. NIJ level III plates will stop 7.62x51. https://www.ojp.gov/pdffiles1/nij

I think you're thinking of IIIA, which is only rated to stop pistol/shotgun calibers. NIJ level III plates will stop 7.62x51. https://www.ojp.gov/pdffiles1/nij/nlectc/250144.pdf https://www.ojp.gov/pdffiles1/nij/nlectc/250144.pdf