The Sig Sauer P320 is a semi-auto pistol made by Sig that uses a striker-fired system instead of the DAO (Double Action Only) mechanism used in the Sig P250.
The Sig P320 is most commonly chambered in 9mm (9x19mm Parabellum) but is also available in .40 S&W, .357 SIG, .45 ACP and 10mm Auto.
The 9mm P320 was first introduced in January 2014. The P320 .45 ACP Compact was announced at SHOT SHOW a year later in January 2015.
There are now over 40 different configurations of the Sig Sauer P320, but all of these models will be chambered in one of the mentioned calibers.