A firearm noise suppressor attachable to the muzzle of a barrel having a longitudinal bore axis. It includes a housing with an outer wall, a forward end wall, and a rearward end wall. The rearward end wall attaches to a firearm barrel and the forward end wall includes an outlet opening aligned with the longitudinal bore axis. A blast chamber is defined at least in part by the rearward end wall, the outer wall, and a blast baffle. At least a second baffle is situated forward of the blast baffle and supported at a periphery by the outer wall. A plurality of circumferentially spaced apart helical blast vanes in the blast chamber impart a rotational flow to propellant gas.