The Ruger SP-101 is a series of double action revolvers produced by the American company Sturm, Ruger. The SP101 is a small frame and all-steel construction carry revolver, with a 5-shot (.38 Special, .357 Magnum, and 9x19mm Parabellum), 6-shot (.327 Federal Magnum and .32 H&R Magnum), or 8-shot (.22 LR) cylinder. The SP-101 is manufactured in .357 Magnum, .38 Special, .327 Federal Magnum, and .22 LR. Barrel lengths 21⁄4" (57.15mm), and 31⁄16" (77.79mm) with full underlugs. 4" (101.6 mm) with half underlug.