Device to improve accuracy of a small arm

Abstract

An insert assembly for a weapon is disclosed. The weapon may be a rifle, such as an M4 carbine. The insert assembly is configured to support a bolt while the bolt moves during recharging and firing cycles. The insert may be configured to continuously press on an upper receiver when the rifle is assembled. These features improve shooting accuracy of the rifle by minimizing and/or making consistent movements of the rifle's internal components (i.e., there is less wobbling of the components with respect to each other). The insert assembly may include a support plate and a hollow protrusion rigidly attached to the plate. A piston and a spring are inserted into the protrusion. The piston slides within the protrusion and is pushed against the bolt of the rifle by the spring.

1 . An insert assembly for a weapon, the insert assembly comprising:
 a support plate that is received in a lower receiver of the weapon;   a hollow protrusion rigidly attached to the support plate and extending upward relative to a top surface of the support plate;   a piston inserted into the hollow protrusion, the piston sliding inside the hollow protrusion, the piston including a top surface to support a bolt of the weapon when the bolt slides over the top surface of the piston; and   a spring inserted into the hollow protrusion between the piston and the top surface of the support plate, the spring exerting a force on the piston, thereby pushing the piston against the bolt.   
     
     
         2 . The insert assembly of  claim 1 , wherein the top surface of the piston is substantially parallel to the top surface of the support plate. 
     
     
         3 . The insert assembly of  claim 1 , wherein the hollow protrusion and the piston include aligning features to control the orientation of the piston with respect to the support plate. 
     
     
         4 . The insert assembly of  claim 1 , wherein the top surface of the piston includes a chamfer. 
     
     
         5 . The insert assembly of  claim 4 , wherein the chamfer locates a bolt keyway when the bolt moves reciprocally between two working positions during firing and reloading. 
     
     
         6 . The insert assembly of  claim 1 , wherein any of the support plate, the hollow protrusion, and the spring are made of stainless steel. 
     
     
         7 . The insert assembly of  claim 1 , wherein the hollow protrusion includes a positive stop feature to limit an upmost position of the piston. 
     
     
         8 . The insert assembly of  claim 1 , wherein the spring exerts a force of between about 5 lbs and about 15 lbs on the piston when the top surface of the piston is in an upmost position. 
     
     
         9 . The insert assembly of  claim 1 , wherein the spring exerts a force of about 10 lbs on the piston when the top surface of the piston is in an upmost position. 
     
     
         10 . The insert assembly of  claim 1 , wherein the piston extends out of the hollow protrusion about 0.5 inches when the top surface of the piston is in an upmost position. 
     
     
         11 . The insert assembly of  claim 1 , wherein the top surface of the piston conforms to a profile of the bolt. 
     
     
         12 . The insert assembly of  claim 1 , further comprising a second protrusion attached to the support plate and extending upward from the top surface of the support plate in the same direction as the hollow protrusion, the second protrusion including a second top surface that presses on an upper receiver of the weapon when the upper receiver is engaged with the lower receiver. 
     
     
         13 . The insert assembly of  claim 12 , wherein friction maintains the insert assembly in position with respect to other components of the weapon. 
     
     
         14 . The insert assembly of  claim 12 , wherein the second top surface is formed from a compressible material. 
     
     
         15 . The insert assembly of  claim 12 , wherein the second top surface is formed from Santoprene™ TPV 111-35. 
     
     
         16 . The insert assembly of  claim 12 , wherein the second top surface extends upward from the second protrusion to engage the upper receiver of the weapon. 
     
     
         17 . The insert assembly of  claim 12 , wherein the second top surface compresses about 0.125 inches while engaging the upper receiver of the weapon. 
     
     
         18 . An insert assembly for a weapon, the insert assembly comprising:
 a support plate received in a lower receiver of the weapon; and   a protrusion attached to the support plate and extending away from a top surface of the support plate, the protrusion including a top surface that presses on an upper receiver of the weapon when the upper receiver is engaged with the lower receiver.   
     
     
         19 . The insert assembly of  claim 18 , wherein friction maintains the insert assembly in position with respect to other components of the weapon. 
     
     
         20 . An insert assembly for a weapon, the insert assembly comprising:
 a support plate that is received in a lower receiver of the weapon;   a hollow protrusion rigidly attached to the support plate and upward relative to a top surface of the support plate;   a piston inserted into the hollow protrusion, the piston sliding inside the hollow protrusion, the piston including a top surface to support a bolt of the weapon, the top surface of the piston including a chamfer to locate a bolt keyway when the bolt moves reciprocally between two working positions during firing and reloading;   a spring inserted into the hollow protrusion between the piston and the top surface of the support plate, the spring exerting a predetermined force of between about 5 lbs and about 15 lbs on the piston, thereby pushing the piston against the bolt; and   a second protrusion attached to the support plate, the second protrusion including a top surface that presses on an upper receiver of the weapon when the upper receiver is engaged with the lower receiver.