SIG Sauer P320
9x39 or .357 SIG or .40 S&W or .45 ACP
The P320 was chosen in 2017 to be the new US military standard sidearm, replacing the M9 Beretta M92FS, with a few adjustments and known as the M17 (and the compact version, designated M18).
Most are produced in Coyote Brown and is shown here with the 21 round magazine. It has also been adopted by 20 US law enforcement agencies.