Patent ID: 6868770

Claim:
A gas porting structure for an autoloading gun having a cylindrical barrel having an outer cylindrical surface portion and a cylindrical inner bore surface and a discharge gas operated shell ejection means having a discharge gas cylinder and piston in gas flow communication with gas porting means provided thru the wall of said barrel and communicating directly with the bore thereof, wherein said piston is affixed to a bolt carrier assembly having a shell extractor means, whereby flow of discharge gas into said cylinder will force said piston rearwardly to retract the bolt carrier assembly, actuate the shell extractor means and eject a shell, wherein said porting means comprises a lateral cut out completely thru a wall section of said barrel and gas porting insert means positioned in said cut out, said insert means having an outer surface and an inner surface formed on concentric radii and respectively, which radii and are the same as outer radius and bore radius respectively of the barrel said insert means having the same length, thickness and width as said cut out and being fitted into said cut out with substantial precision whereby said inner surface becomes a section of the barrel bore, wherein at least one gas port is formed thru said insert means and wherein edge portions of said inner surface which outline said at least one gas port are curved such as to eliminate any sharp edge portions on which firing debris could be snagged.