The 9 mm and .40 S&W versions use double-column box magazines; the 9 mm has a 15-round capacity, and the .40 S&W has a 10-round or 12-round capacity. The .45 ACP versions use single-column magazines holding seven or eight rounds (depending on the model). All P-series pistols of the same caliber use a similar magazine design, but slight modifications have been made to at least the 9 mm guns so that not all P-series magazines will function in all P-series frames. Ruger did not keep track of the magazine models so an older magazine may not secure in a newer frame. The Ruger Police Carbine also uses P-series magazines. The P-series pistols have an ambidextrous magazine release located behind the trigger guard; it can be pushed forward from either side to eject the magazine.