Abstract: A hand guard removably mountable on the barrel of a firearm such as a rifle. The hand guard is formed in two complementary mating housing components joined in a vertical plane which contains the longitudinal axis of the barrel. The housing components together define a convection chamber which envelops a substantial length of the barrel of the firearm. The joined housing components are generally of pear-shaped cross section having a broadened, flattened bottom member and a narrow, tall chimney member. Heat from the barrel of the firearm creates convection currents in the convection chamber as cooling air is drawn through inlet ports in the bottom member, around the barrel, and out through exhaust ports in sidewalls of the chimney member. A heat shield is carried by each of the housing components and is positioned between the barrel and the outer housing.