Biased pivoting cartridge extractor for blowback bolt firearms

Abstract

A biased pivoting spent ammunition cartridge case extractor and retainer mechanism for blowback bolt firearms. The mechanism includes a distal arcuate hook shaped and dimensioned to intimately engage and nest into part of the circumferential groove in front of the cartridge rim. The hook remains engaged during blowback extraction of the casing from the chamber, and prior to ejection of the case from the firearm. The hook is formed onto the distal end of a rocking member secured to the bolt by a medial pivot. A compression spring bears against the opposite, proximal end of the rocking member thereby biasing the hook inwardly toward the counterbore seat on the distal end of the bolt into which the base of the case rests during extraction. A direct gas impingement system overcomes the biasing force of the spring to cause the case to be ejected.

What is claimed is: 
     
         1 . In a firearm having a bolt reciprocatingly sliding axially along a bolt axis, said bolt temporarily engaging an ammunition cartridge at a distal bolt seat during a firing cycle, wherein said ammunition cartridge includes a case portion having a proximal rim adjacent to a circumferential groove, an improvement which comprises:
 an extractor assembly which comprise:
 an oblong rocking member comprising a hook radially moveable with respect to said bolt; and, 
 said oblong rocking member being pivotingly secured to said bolt at a pivot. 
   
     
     
         2 . The improvement of  claim 1 , wherein said hook is biased radially inwardly by a biasing force. 
     
     
         3 . The improvement of  claim 2 , wherein said biasing force is overcomeable by an ejector selected from the group consisting of a mechanical ejector, and direct gas impingement of pressurized gaseous forces generated during said firing cycle. 
     
     
         4 . The improvement of  claim 3 , wherein said pressurized gaseous forces comprise a radial component impacting said case portion during an ejection stage of said firing cycle. 
     
     
         5 . The improvement of  claim 2 , which further comprises a spring between said bolt and said rocking member, said spring providing said biasing force. 
     
     
         6 . The improvement of  claim 5 , wherein said rocking member comprises:
 a distal end portion carrying said hook;   a proximal end portion; and,   a medial portion secured to said pivot.   
     
     
         7 . The improvement of  claim 6 , wherein said spring comprises a first terminus bearing against said bolt and a second terminus bearing against said proximal end portion of said extractor member. 
     
     
         8 . The improvement of  claim 7 , wherein said pivot comprises a pivot pin defining an extractor axis of rotation; said pivot pin having a substantially cylindrical post rotatively engaging a substantially cylindrical bearing. 
     
     
         9 . The improvement of  claim 8 , wherein said extractor axis of rotation is perpendicular to said bolt axis. 
     
     
         10 . The improvement of  claim 1 , wherein said rocking member moves within a recess formed into said bolt. 
     
     
         11 . The improvement of  claim 1 , wherein said rocking member rocks within a plane angularly inclined between about 66.5 degrees and about 68.5 degrees from vertical with respect to the firearm in a upright orientation. 
     
     
         12 . The improvement of  claim 1 , wherein said hook comprises a concave arcuate tip shaped and dimensioned to intimately nest against a convex surface of said circumferential groove; and, wherein said concave arcuate tip is further dimensioned to have an axial dimension less than the axial dimension of said circumferential groove. 
     
     
         13 . The improvement of  claim 12 , wherein said arcuate tip and curved outer surface of said cartridge have commensurate radii of curvature. 
     
     
         14 . The improvement of  claim 13 , wherein said hook further comprises a pair of convex corners at the angular extremities of said arcuate tip. 
     
     
         15 . In a method for securing a spent ammunition cartridge case against a seat of a bolt during a firing cycle prior to ejection of said case from a firearm, said cartridge case having a proximal rim adjacent to a circumferential groove, an improvement which comprises:
 contacting a proximal rim of said case against said seat; and,   simultaneously to said contacting, engaging said circumferential groove of said case by a hook of an extractor member pivotingly mounted to said bolt.   
     
     
         16 . The improvement of  claim 15 , which further comprises radially biasing said hook against said case. 
     
     
         17 . The improvement of  claim 16 , wherein said radially biasing occurs with a force overcomeable by direct gas impingement forces generated by during said firing cycle.