Improved firearm

Abstract

An improved firearm includes in some embodiments a gas block of an indirect impingement system mounted on the barrel near the firing chamber to provide gas at a higher pressure for moving the piston that moves the bolt carrier. Some embodiments include low frictions rails on which the bolt carrier moves within the upper receiver. The higher gas pressure and the reduced friction from the rails reduce the required stroke of the piston, allowing a shorter firearm to be constructed. In some embodiments, mating elements, such as pins and corresponding openings, on the upper receiver and the lower receiver, align and provide additional structural strength to the upper and lower receiver.

We claim as follows: 
     
         1 . An improved autoloading firearm, comprising:
 a receiver, comprising an upper and lower receiver, said upper and lower receiver having mating surfaces and being separable from each other, the upper receiver having an internal cavity;   a barrel affixed to the forward end of the receiver, the barrel having having a breech configured to receive ammunition and a muzzle, from which a projectile exits upon firing;   protrusions from said upper or lower receiver mating surfaces which mate with aligned openings on the opposite upper or lower receiver;   a bolt carrier disposed within the upper receiver cavity, the bolt carrier having a firing position and a retracted position defining a longitudinal axis of movement;   one or more removable rail members mounted within the receiver and aligned with the longitudinal axis of movement of the bolt carrier, the rail members supporting and guiding the bolt carrier during movement of the bolt carrier;   a transverse gas bore penetrating through the barrel through which high-pressure combustion gas passes upon firing, the gas bore being closer to the breech than to the muzzle;   a gas block configured to receive high-pressure combustion gas from the gas bore;   a gas piston being acted upon by said high-pressure combustion gas to generate a retraction force;   a pushrod for transmitting the retraction force, the pushrod being mechanically connected to the gas piston and;   a carrier key mechanically connected to said bolt carrier, receiving said retraction force from the pushrod, wherein the retraction force causes movement of the bolt carrier towards the retracted position.   
     
     
         2 . The improved firearm type firearm of  claim 1  in which the coefficient of friction between the rail members and the bolt carrier is less than that of between the bolt carrier and the internal surface of the upper receiver cavity. 
     
     
         3 . The improved firearm of  claim 1  in which the pushrod is formed as part of the gas piston. 
     
     
         4 . The improved firearm of  claim 1  in which pushrod separates from the carrier key before the bolt carrier reaches the retracted position. 
     
     
         5 . The improved firearm of  claim 1  in which the improved firearm is an M16-type firearm. 
     
     
         6 . An improved firearm, comprising:
 an upper receiver having an upper receiver cavity;   a bolt carrier disposed within the upper receiver cavity and moving along a longitudinal axis between a firing position and a retracted position; and   one or more rails mounted within the upper receiver, the rails supporting and guiding the bolt carrier during movement.   
     
     
         7 . The firearm of  claim 6  in which the one or more rails are removable. 
     
     
         8 . The firearm of  claim 6  in which the coefficient of friction between the one or more rails and the bolt carrier is less than that of between the bolt carrier and the internal surface of the upper receiver cavity. 
     
     
         9 . The firearm of  claim 6  in which the bolt carrier and the upper receive include grooves for accepting a portion of the one or more rails. 
     
     
         10 . The firearm of  claim 6  in which the one or more rails have circular cross sections. 
     
     
         11 . The firearm of  claim 6  in which the one or more rails include a concave surface. 
     
     
         12 . The firearm of  claim 6  in which the rails are removably affixed to the interior of the upper receiver cavity. 
     
     
         13 . The firearm of  claim 6  in which the rails are affixed to the outer surface of the bolt carrier. 
     
     
         14 . The firearm of  claim 6  in which the rails substantially reduce or eliminate the need for lubrication of the bolt carrier. 
     
     
         15 . The firearm of  claim 6  in which the rails comprised a low-friction, high-temperature material. 
     
     
         16 . The firearm of  claim 6  in which the rails comprise carbon or a carbon composite. 
     
     
         17 . The firearm of  claim 16  in which the rails comprise polymer and chopped carbon fiber 
     
     
         18 . The firearm of  claim 6  in which the rails comprise metal. 
     
     
         19 . The firearm of  claim 6  in which the rails are disposed in longitudinal receiving areas machined into the bolt carrier and the upper receiver. 
     
     
         20 . The firearm of  claim 19  in which the rails are retained within to the upper receiver housing by fixtures. 
     
     
         21 . The firearm of  claim 20  in which the fixtures comprise any combination of:
 posts, bolts, screws, pins, clips. 
 
     
     
         22 . The firearm of  claim 6  in which the improved firearm is an M16-type firearm. 
     
     
         23 - 38 . (canceled) 
     
     
         39 . An improved autoloading M16-type firearm, comprising:
 a receiver, comprising an upper and lower receiver, said upper and lower receiver having mating surfaces and being separable from each other, the upper receiver having an internal cavity;   a barrel affixed to the forward end of the receiver, the barrel having a breech configured to receive ammunition and a muzzle, from which a projectile exits upon firing; and   one or more protrusions from said upper or lower receiver mating surfaces, said protrusions mating with aligned openings on the opposite upper or lower receiver.   
     
     
         40 . The firearm of  claim 39 , wherein the one or more protrusions are posts which protrude perpendicular to the mating surfaces. 
     
     
         41 . The firearm of  claim 39 , wherein the one or more protrusions are removable from the upper or lower receiver. 
     
     
         42 . The firearm of  claim 39 , wherein the one or more protrusions are integrated into the upper receiver and mate with corresponding aligned openings in the lower receiver. 
     
     
         43 . The firearm of  claim 39 , wherein the one or more protrusions are integrated into the lower receiver and mate with corresponding aligned openings in the upper receiver. 
     
     
         44 . The firearm of  claim 39 , wherein the one or more protrusions comprises protrusions on both the upper and lower receivers, with corresponding aligned openings on the opposite receivers. 
     
     
         45 . The firearm of  claim 39 , wherein the one or more protrusions on an upper or lower receiver are arranged such that they do not interfere with mating of the upper or lower receiver with a corresponding receiver which does not have aligned openings. 
     
     
         46 . The firearm of  claim 39 , wherein the one or more protrusions are monolithic protrusions.