Introduced in 1972, the Security-Six was the original model of the new series.
The majority of these guns were manufactured with adjustable sights, though a few early models were sold with fixed sights.
Security-Sixes could be ordered with either service or "target" (combat) -style square butt grips.
 Nearly all Security-Sixes were chambered for the .357 Magnum cartridge, which also permitted the use of the shorter .38 Special cartridge.
 Ruger also chambered the Security-Six in .38 Special for some police orders by fitting different cylinders that could only accommodate the .38 Special cartridge.
Barrel lengths available on the Security-Six included 2.75, 4, and 6 inches.

The .357 Magnum, four inch barreled model was standard issue to uniformed officers of the former U.S. Immigration and Naturalization Service as well as Patrol Agents of the U.S. Border Patrol until both agencies adopted .40 caliber semi-automatic pistols.
Introduced in 1972, the Security-Six was the original model of the new series. The majority of these guns were manufactured with adjustable sights, though a few early models were sold with fixed sights. Security-Sixes could be ordered with either service or "target" (combat) -style square butt grips.  Nearly all Security-Sixes were chambered for the .357 Magnum cartridge, which also permitted the use of the shorter .38 Special cartridge.  Ruger also chambered the Security-Six in .38 Special for some police orders by fitting different cylinders that could only accommodate the .38 Special cartridge. Barrel lengths available on the Security-Six included 2.75, 4, and 6 inches.
The .357 Magnum, four inch barreled model was standard issue to uniformed officers of the former U.S. Immigration and Naturalization Service as well as Patrol Agents of the U.S. Border Patrol until both agencies adopted .40 caliber semi-automatic pistols.
Ruger Security-Six