A hand guard comprising: an elongated housing comprising: a lumen configured to receive an intermediate portion of a barrel of a firearm longitudinally therein, a side wall (238, 241), a pair of elongated slots (254A, 254B) disposed on opposite sides of the side wall, wherein each of the elongated slots defines a corresponding angulated face of a rail adapted to receive an accessory to be mounted thereon, an upper part and a lower part adapted to be releasably coupled together to provide the lumen, wherein the housing comprises one or more protrusions configured to engage a receiver of the firearm, and opposite open ends; and an expansion collar disposed at one end of and extending from the housing, and comprising an expansion mechanism configured to adjustably compress the expansion collar and the lower part of the housing longitudinally between a pair of oppositely facing surfaces (34, 36) of the firearm respectively disposed at opposite ends of the intermediate portion of the barrel, wherein the expansion mechanism comprises: a plurality of longitudinal tongues extending toward an adjacent end of the lower part of the housing; a plurality of longitudinally extending screws respectively received in corresponding ones of a plurality of bores contained in the expansion collar such that a distal end of each screw is disposed in abutment with a bottom end surface of a corresponding one of the bores and at least a portion of each screw is loaded in compression, and a plurality of elongated compression members extending longitudinally from an end of the expansion collar opposite to an adjacent end of the lower part of the housing, wherein the compression members compress or expand locally to ensure that the force exerted by the screws is uniformly distributed among the compression members. an elongated housing comprising: a lumen configured to receive an intermediate portion of a barrel of a firearm longitudinally therein, a side wall (238, 241), a pair of elongated slots (254A, 254B) disposed on opposite sides of the side wall, wherein each of the elongated slots defines a corresponding angulated face of a rail adapted to receive an accessory to be mounted thereon, an upper part and a lower part adapted to be releasably coupled together to provide the lumen, wherein the housing comprises one or more protrusions configured to engage a receiver of the firearm, and opposite open ends; and a lumen configured to receive an intermediate portion of a barrel of a firearm longitudinally therein, a side wall (238, 241), a pair of elongated slots (254A, 254B) disposed on opposite sides of the side wall, wherein each of the elongated slots defines a corresponding angulated face of a rail adapted to receive an accessory to be mounted thereon, an upper part and a lower part adapted to be releasably coupled together to provide the lumen, wherein the housing comprises one or more protrusions configured to engage a receiver of the firearm, and opposite open ends; and an expansion collar disposed at one end of and extending from the housing, and comprising an expansion mechanism configured to adjustably compress the expansion collar and the lower part of the housing longitudinally between a pair of oppositely facing surfaces (34, 36) of the firearm respectively disposed at opposite ends of the intermediate portion of the barrel, wherein the expansion mechanism comprises: a plurality of longitudinal tongues extending toward an adjacent end of the lower part of the housing; a plurality of longitudinally extending screws respectively received in corresponding ones of a plurality of bores contained in the expansion collar such that a distal end of each screw is disposed in abutment with a bottom end surface of a corresponding one of the bores and at least a portion of each screw is loaded in compression, and a plurality of elongated compression members extending longitudinally from an end of the expansion collar opposite to an adjacent end of the lower part of the housing, wherein the compression members compress or expand locally to ensure that the force exerted by the screws is uniformly distributed among the compression members. a plurality of longitudinal tongues extending toward an adjacent end of the lower part of the housing; a plurality of longitudinally extending screws respectively received in corresponding ones of a plurality of bores contained in the expansion collar such that a distal end of each screw is disposed in abutment with a bottom end surface of a corresponding one of the bores and at least a portion of each screw is loaded in compression, and a plurality of elongated compression members extending longitudinally from an end of the expansion collar opposite to an adjacent end of the lower part of the housing, wherein the compression members compress or expand locally to ensure that the force exerted by the screws is uniformly distributed among the compression members.