20MM

20mm covers large caliber automatic cannon ammunition and related components used in military aircraft, naval, and ground based weapon systems. This category includes complete cartridges, projectile-only examples, practice and drill rounds, inert dummies, sectioned training pieces, belt links, and case variants representing both operational and instructional use.

Items in this section reflect the technical complexity of 20mm systems, with variations in projectile type, materials, color coding, and internal construction. Common examples include practice, armor piercing, incendiary, and dummy configurations produced for testing, training, and logistics. Because many 20mm rounds were manufactured under specific contracts and markings, this category is especially useful for collectors studying military production, ammunition identification, and ordnance development across the mid to late twentieth century.