MIL-P-85723, MILITARY SPECIFICATION: PROJECTILE, 20 MILLIMETER, SEMI-ARMOR PIERCING, HIGH EXPLOSIVE INCENDIARY, PGU-28/B (12 AUG 1986) [NO S/S DOCUMENT]., This specification establishes the production and acceptance requirements for the Projectile, 20 millimeter (mm) Semi-Armor Piercing, High Explosive Incendiary Projectile (SAPHEI), PGU-28/B, referred herein as the "projectile".