The round-butt 3" Model 13 was the specific FBI contract specification — a compact .357 Magnum K-Frame that fit more naturally in plainclothes holsters. The round butt reduces printing under clothing compared to the standard square-butt configuration. Type: Revolver Action: Double-Action Caliber: 357 Magnum Capacity: 6 Year introduced: 1974, USA Weight: 29.5 oz Overall length: 8" Status: Discontinued Intended use: Law Enforcement / Concealed Carry