Abstract: A firearm sound suppressor (12) has a baffle tube (20) and an exterior tube (14) which are concentrically disposed to define a single expansion chamber (56) there-between. A muzzle cap (16) encloses a first end of the expansion chamber (56) and has a plurality of flow ports (36) which provide fluid communication between a gun barrel muzzle and the expansion chamber (56). An end cap (18) encloses a second end of the expansion chamber (56). The end cap (18) has a bullet port (46) and vent ports (48) which extend circumferentially around the bullet port (46). Baffles (22) of tubular shape are pressed into the baffle tube (20) to provide a baffle stack (66). The baffles (22) have interiorly disposed upsets (78) which defines a gas check feature, causing spent propellant gases move into the entire volume of the expansion chamber (56) to reduce muzzle blast pressures.