The .223 Remington is a rifle cartridge, originally developed in 1957 as a commercial hunting bullet for small mid-western varmints; with the first rifle chambered for it coming out in 1963. It has continued to be a popular civilian hunting cartridge.
Bullet diameter: 0.224 in (5.7 mm)
Case length: 1.76 in (45 mm)
Case capacity: 28.8 grain H2O (1.87 ml)
Parent case: .222 Remington
Maximum pressure (SAAMI): 55,000 psi (380 MPa)
Shoulder diameter: 0.354 in (9.0 mm)
Rim diameter: 0.378 in (9.6 mm)