Low-recoil firearm with noncircular guide rod for angularly locating bolt carrier assembly

A gas operated firearm comprising:

• a gas cylinder operative to receive gas when the firearm is fired;
• gas piston means normally received in said gas cylinder and operative to move along a movement path including movement outside of the gas cylinder, in response to gas pressure;
• an action spring urging said gas piston means to return to said gas cylinder;
• a single guide rod having a noncircular cross-section and extending along the entire movement path of said gas piston means;
• and
• said gas piston means has a noncircular opening complementary to the noncircular cross-section of said single guide rod and is slidably mounted on said single guide rod, so that the gas piston means is slidably and nonrotatably supported on the guide rod, the complementary noncircular opening of the gas piston means coacting with the noncircular single guide rod to maintain the gas piston means in fixed angular alignment on the guide rod, and the gas piston means, guide rod, and action spring are substantially concentric along the movement path of the gas piston,
• whereby the single noncircular guide rod and the complementary noncircular opening cooperate to maintain said gas piston means in fixed angular position while moving along the entire movement path.

A firearm comprising:

• a receiver section;
• guide rod means having a back end portion in spaced apart relation behind the receiver section, and also having a forward end portion;
• a buttplate attached to the back end portion of said guide rod means and held by the guide rod means in spaced apart relation in back of the receiver section;
• a barrel in fixed relation to said receiver section;
• mounting means affixed to said barrel in juxtaposition with said forward end portion of said guide rod means;
• said forward end portion of said guide rod means being longitudinally movable with respect to said mounting means and selectably engaging said mounting means at a certain fixed longitudinal position relative to the mounting means when said firearm is in assembly, thereby keeping the mounting means at a predetermined maximum distance from said buttplate so as to keep said firearm in assembly;
• and
• stock means engaging said buttplate and rigidly extending forwardly from said buttplate in laterally spaced relation to said receiver section to engage said mounting means at said predetermined longitudinal position relative to the buttplate and thereby prevent the guide rod means and affixed buttplate from moving forwardly relative to said mounting means,
• whereby said stock means maintains said barrel and mounting means in assembly relative to said buttplate and guide rod means, so that the stock means must be removed to permit relative movement and disassembly thereof.

A gas operated firearm comprising:

• means defining a buttplate at the rear of the firearm for resting against the shoulder of a shooter;
• a barrel;
• means defining a gas cylinder affixed to said barrel and in gas flow communication with the barrel;
• guide rod means extending from said buttplate to said gas cylinder;
• means providing a gas piston reciprocably carried on said guide rod means so that the guide rod means extends through said gas piston;
• action spring means operative to urge said gas piston forwardly along said guide rod means, whereby said gas piston can travel rearwardly on said guide rod means toward said buttplate in response to gas from said barrel entering said gas cylinder;
• said guide rod means extending into said gas cylinder through an opening in the base of the gas cylinder to terminate at a forward end;
• tip means secured to said forward end of the guide rod means;
• said tip means having a portion of reduced area immediately in front of the base of said gas cylinder to receive a retaining means, and having a portion of relatively enlarged area in front of said reduced area to engage said retaining means when the guide rod is urged rearwardly by said action spring means to bring said retaining means into contact with said gas cylinder;
• at least a forward portion of said guide rod means being hollow;
• said reduced area portion of said tip means being secured within the hollow forward end of said guide rod means, with said enlarged portion being spaced apart from said forward end to define a necked region for receiving the retaining means;
• the portion of said tip means within the hollow forward end of the guide rod means being solid and extending into a portion of the guide rod within said gas cylinder;
• and
• means defining a gas flow passageway transversely extending through said guide rod means and the tip means within, at a gas receiving location in the gas cylinder,
• so that the gas can flow through said passageway to act more uniformly on said gas piston means carrier on the guide rod means.

A firearm comprising:

• a single elongate guide rod means having noncircular cross-section and extending longitudinally of the firearm;
• bolt carrier means supported by said single guide rod means for reciprocal movement along the single guide rod means between a forward position and a rearward position;
• said bolt carrier means including means defining a longitudinal opening of noncircular cross-section complementary to the noncircular cross-section of the guide rod means and providing a complementary sliding fit on said single guide rod, so that the sliding fit of said complementary noncircular guide rod means within said noncircular opening maintains the guide rod means fixed at a certain angular position on the guide rod means during reciprocal movement;
• means defining a receiver section including a pair of spaced apart surfaces flanking said bolt carrier means when in a forward position along said guide rod means;
• said guide rod means extending behind said receiver section to permit the bolt carrier means to travel behind said spaced apart surfaces during rearward movement of the bolt carrier means;
• extractor means movable with said bolt carrier means to travel behind said receiver section during said rearward movement of the bolt carrier means;
• said extractor means including a pair of mutually spaced apart arms slidably extending longitudinally within said spaced apart surfaces when said extractor means is within said receiver section;
• and
• said extractor arms having forward ends bowed inwardly to help guide said bolt carrier means for returning between said spaced apart surfaces as the bolt carrier means moves forwardly from said rearward position behind the spaced apart surfaces.

A firearm comprising:

• means defining a buttplate at the rear of the firearm for resting against the shoulder of a shooter;
• a barrel;
• means defining a gas cylinder affixed to said barrel and in gas flow communication with the barrel;
• guide rod means secured to said buttplate and extending forwardly from said buttplate into rigid engagement with said gas cylinder means and operative to maintain the gas cylinder means at a predetermined maximum longitudinal spacing from the buttplate;
• means providing a gas piston supported on said guide rod means for reciprocal movement therealong so that the guide rod means extends through said gas piston whereby reaction force is mechanically coupled from the gas cylinder to the buttplate by the guide rod means;
• action spring means operative to urge said gas piston forwardly along said guide rod means, whereby said gas piston can travel rearwardly on said guide rod means toward said buttplate in response to gas from said barrel entering said gas cylinder;
• securement means releasably securing the guide rod means to the buttplate;
• stock means having a back portion removably engaging said buttplate;
• and
• said stock means extending rigidly forward from said back portion and selectably operatively engaging said gas cylinder means to maintain said predetermined longitudinal spacing from said buttplate, so that the stock means prevents the gas cylinder means from moving rearwardly on the guide rod means toward the buttplate,
• whereby the firearm normally is held in assembly by rigid engagement of the guide rod means with the gas cylinder means and by the stock means rigidly extending between the buttplate and the gas cylinder means, and whereby the gas cylinder means can move rearwardly on the guide rod means for disassembling the firearm only when the rigid stock means is removed from engagement with the buttplate and the gas cylinder means.

A firearm comprising:

• a single elongate guide rod means having noncircular cross-section and extending longitudinally of the firearm;
• bolt carrier means supported by said single guide rod means for reciprocal movement along the single guide rod means between a forward position and a rearward position;
• said bolt carrier means including means defining a longitudinal opening of noncircular cross-section complementary to the noncircular cross-section of the guide rod means and providing a complementary sliding fit on said single guide rod, so that the sliding fit of said complementary noncircular guide rod means within said noncircular opening maintains the guide rod means fixed at a certain angular position on the guide rod means during reciprocal movement;
• means defining a receiver section including a pair of spaced apart surfaces flanking said bolt carrier means when in a forward position along said guide rod means;
• and
• said guide rod means extends behind said receiver section to permit the bolt carrier means to travel behind said spaced apart surfaces during rearward movement of the bolt carrier means,
• so that the single noncircular guide rod means and the complementary noncircular opening in the bolt carrier means cooperate to maintain the bolt carrier means in fixed angular alignment on the single guide rod means while the bolt carrier means is behind the receiver section surfaces.