Firearm receiver systems offering a fixed barrel arrangement and pressure relief capability

A firearm receiver system, comprising:

• a receiver including a handguard mounting body defining a front end portion of the receiver and a central bore configured for having a bolt carrier slidably disposed therein, and wherein the central bore includes a barrel-receiving receptacle at least partially located within the handguard mounting body;
• a handguard including a handguard mounting body receptacle at a first end portion thereof, wherein the handguard mounting body receptacle includes a plurality of interior surfaces each matingly engaged with a corresponding one of a plurality of exterior surfaces of the handguard mounting body;
• and
• a bolt energizing device, wherein the handguard mounting body and the handguard jointly define a bolt energizing device receptacle for accommodating the bolt energizing device in a fixed orientation relative to the receiver;
• wherein one of said interior surfaces of the handguard mounting body receptacle is a bolt energizing device engaging surface thereof;
• wherein one of said exterior surfaces of the handguard mounting body is at least partially defined by a bolt energizing device engaging portion of the receiver;
• wherein the bolt energizing device includes an operating rod that passes through an operating rod passage of the handguard mounting body;
• wherein the operating rod passage extends parallel to a centerline longitudinal axis of the central bore;
• wherein the operating rod passage is located at one of opposing sides of the receiver;
• and
• wherein a top side and a bottom side of the receiver are located between said opposing sides.

A firearm receiver system, comprising:

• a receiver including a handguard mounting body defining a front end portion of the receiver and a central bore configured for having a bolt carrier slidably disposed therein, and wherein the central bore includes a barrel-receiving receptacle at least partially located within the handguard mounting body;
• a handguard including a handguard mounting body receptacle at a first end portion thereof, wherein the handguard mounting body receptacle includes a plurality of interior surfaces each matingly engaged with a corresponding one of a plurality of exterior surfaces of the handguard mounting body;
• and
• an ammunition belt feed assembly integral with the receiver;
• wherein one of said interior surfaces of the handguard mounting body receptacle is a bolt energizing device engaging surface thereof;
• and
• wherein one of said exterior surfaces of the handguard mounting body is at least partially defined by a bolt energizing device engaging portion of the receiver.