Over last few decades, Al-based metal matrix composites (MMCs) have become a promising material of choice for lightweight armors in vehicles. Recent development in ultra-fine-grain and nanostructured material technology provides a new opportunity for the substantial strength enhancement of MMCs unattainable with the conventional microstructure of microscale, leading to significant weight reduction in armor packages. In this article, we will present the latest development of a novel class of nanostructured metal matrix composites (NMMCs) based on submicron SiC particulates reinforced nanocrystalline Al alloys. The successful fabrication of large-dimension NMMCs plates with a cost-effective synthesis and consolidation process that can be scaled up for mass production will be demonstrated. The microstructure, processing, mechanical properties, and their correlations of this class of NMMCs will also be reported. The ballistic performance of the NMMCs is investigated through a real test of high-speed machinegun bullets, and a numerical modeling as well.