automag
The .44 Auto Mag pistol (AMP) is a semi-automatic handgun designed between 1966 and 1971 by the Auto Mag Corporation, chambered in propietary .44 AMP cartridge. The weapon features a bolt housed inside the upper receiver, ventilated rib on its exposed barrel, and a M1911-style trigger.
It is Harry Callahan's alternate weapon in his fourth movie of the Dirty Harry series, Sudden Impact.