Cartridge chamber for automatic firearm

In an automatic firearm having a breech mechanism, with a cartrige chamber having a bullet chamber portion formed in the inner end of the barrel and a powder chamber portion adjacent thereto, and a conical transition portion therebetween serving as a stop for the cartridge, said transition portion being provided with gas pressure balance grooves, the improvement comprising:

• a tubular member forming said powder chamber portion mounted adjacent to the inner end of the barrel of said firearm and bearing thereagainst;
• a plurality of gas pressure balance grooves in said bullet chamber portion extending longitudinally thereof;
• a plurality of pressure balance grooves in said tubular;
• opposing inner shoulders on the respective opposing ends of the inner end of said barrel and of said tubular member, said shoulders defining together and forming an interiorally open annular groove;
• and
• a cylindrical sealing ring seated within said annular groove against the outside circular wall surface thereof in outwardly spaced relation from the inner longitudinal surfaces of the inner end of said gun barrel and the adjacent end of said tubular member to thereby provide an annular space for the distribution of powder gasses flowing from said pressure balance grooves in said bullet chamber portion to said pressure balance grooves in said tubular member.