An integrally suppressed handgun comprising: a longitudinal axis (LA); a frame ; a receiver attached to the frame ; an elongated barrel insert comprising a rearward mounting portion fixedly coupled to the receiver and a forward retention portion , the barrel insert comprising a rear breech end defining a chamber configured for holding an ammunition cartridge, a front end , and a longitudinally-extending barrel bore defining a projectile pathway (P); the barrel insert further comprising a plurality of radial gas ports in fluid communication with the barrel bore ; a suppressor mounting adapter at least partially surrounding and removably coupled to the barrel insert , the mounting adapter comprising an upper through passage receiving the barrel insert at least partially therein and a lower through passage ; an annular gas expansion chamber formed between the barrel insert and the mounting adapter in the upper through passage ; a threaded muzzle cap removably coupling the mounting adapter to the barrel insert ; a baffle assembly removably coupled to the mounting adapter and defining a front end of the handgun including a projectile exit aperture , the baffle assembly comprising a plurality of sound suppression baffles arranged in longitudinally stacked relationship, each baffle defining an internal baffle gas expansion chamber ; and an elongated mounting rod extending from the front end of the baffle assembly rearward to the mounting adapter , a threaded rear end of the mounting rod threadably coupled to the mounting adapter to retain the baffle assembly; wherein when the handgun is discharged, the annular gas expansion chamber fills with combustion gas vented from the gas ports of the barrel insert . a longitudinal axis (LA); a frame ; a receiver attached to the frame ; an elongated barrel insert comprising a rearward mounting portion fixedly coupled to the receiver and a forward retention portion , the barrel insert comprising a rear breech end defining a chamber configured for holding an ammunition cartridge, a front end , and a longitudinally-extending barrel bore defining a projectile pathway (P); the barrel insert further comprising a plurality of radial gas ports in fluid communication with the barrel bore ; a suppressor mounting adapter at least partially surrounding and removably coupled to the barrel insert , the mounting adapter comprising an upper through passage receiving the barrel insert at least partially therein and a lower through passage ; an annular gas expansion chamber formed between the barrel insert and the mounting adapter in the upper through passage ; a threaded muzzle cap removably coupling the mounting adapter to the barrel insert ; a baffle assembly removably coupled to the mounting adapter and defining a front end of the handgun including a projectile exit aperture , the baffle assembly comprising a plurality of sound suppression baffles arranged in longitudinally stacked relationship, each baffle defining an internal baffle gas expansion chamber ; and an elongated mounting rod extending from the front end of the baffle assembly rearward to the mounting adapter , a threaded rear end of the mounting rod threadably coupled to the mounting adapter to retain the baffle assembly; wherein when the handgun is discharged, the annular gas expansion chamber fills with combustion gas vented from the gas ports of the barrel insert . <EOS>