Patent Publication Number: US-11378347-B2

Title: Buffer with magnetic bias

Description:
BACKGROUND 
     The present invention relates to a buffer assembly for a firearm. The buffer assembly includes at least one magnet that offsets an inertial event that occurs during the firing action of a firearm. 
     SUMMARY 
     The invention provides a buffer assembly for a firearm, the buffer assembly comprising: a buffer tube including a closed rear end; an action spring in the tube; and a buffer in the tube and engaging the action spring, the buffer including a buffer body defining an internal buffer cavity, a rear end cap covering a rear end of the buffer body, a front end cap covering a front end of the buffer body, and an internal assembly within the buffer cavity, the internal assembly comprising at least one weight, a first magnet and a second magnet wherein a magnetic repelling force between the first magnet and the second magnet biases the weight to an at-rest position within the internal assembly; and wherein in response to an inertial event the at least one weight overcomes the bias of the magnetic repelling force to achieve a dead-blow condition to at least partially offset an effect of the inertial event. 
     In some embodiments, the magnetic repelling force establishes a delay interval between the occurrence of the inertial event and the occurrence of the resulting dead-blow condition. In some embodiments, the first magnet is encapsulated with the weight in an encapsulation. In some embodiments, the inertial event is generated by a rearward stroke of the buffer and the dead-blow condition occurs at the beginning of the rearward stroke. In some embodiments, the first magnet is proximate the weight and the second magnet is at least partially disposed within the rear end cap of the buffer body. In some embodiments, the magnetic repelling force adjusts a magnitude of an impact force arising from the dead-blow condition. In some embodiments, the inertial event is generated by a rearward stroke of the buffer and the dead-blow condition occurs at both a beginning of the rearward stroke and an end of the rearward stroke. In some embodiments, the at least one weight includes a first weight and a second weight, the first weight located rearwardly within the buffer body relative to the second weight, the first magnet is positioned proximate the first weight, and the second magnet is positioned proximate the second weight. In some embodiments, the magnetic repelling force resets the internal assembly to the at-rest condition after a recover time has passed following the occurrence of the dead-blow condition. 
     The invention also provides a firing assembly for a firearm, the firing assembly comprising: a bolt carrier movable in a rearward stroke and a forward stroke as part of a firing and loading action of the firearm; and a buffer assembly including a buffer tube including a closed rear end, an action spring in the tube, and a buffer in the tube and engaging the action spring, the buffer including a buffer body defining an internal buffer cavity, a rear end cap covering a rear end of the buffer body, a front end cap engaged with the bolt carrier, and an internal assembly within the buffer cavity, the internal assembly comprising at least one weight, a first magnet, and a second magnet; wherein a magnetic repelling force between the first magnet and the second magnet biases the weight to an at-rest position within the internal assembly; wherein the buffer is driven in rearward and forward strokes corresponding to the rearward and forward strokes of the bolt carrier and under the influence of respective rearward motion of the bolt carrier and a forward biasing force of the action spring; wherein as a result of at least one of the rearward and forward strokes, at least one inertial event occurs; wherein in response to the inertial event the at least one weight overcomes the bias of the magnetic repelling force to achieve a dead-blow condition to at least partially offset an effect of the inertial event. 
     In some embodiments, the magnetic repelling force adjusts a magnitude of an impact force arising from the dead-blow condition. In some embodiments, the magnetic repelling force establishes a delay interval between the occurrence of the inertial event and to the occurrence of the dead-blow condition. In some embodiments, the inertial event is generated by a rearward stroke of the buffer and the dead-blow condition occurs at the end of the rearward stroke. In some embodiments, the second magnet is proximate the weight and the first magnet is at least partially disposed within the front end cap of the buffer body. In some embodiments, a magnetic attracting force between the first magnet and the bolt carrier biases the bolt carrier towards the buffer body. In some embodiments, the first magnet is proximate the weight and the second magnet is at least partially disposed within the rear end cap of the buffer body, wherein the internal assembly further comprises a third magnet disposed at least partially within the front end cap of the buffer body, and wherein a magnetic attracting force between the third magnet and the bolt carrier biases the bolt carrier towards the buffer body. In some embodiments, a radius of the third magnet is larger than a radius of the cavity of the buffer body. In some embodiments, the magnetic repelling force resets the internal assembly to the at-rest condition after a recover time has passed following the occurrence of the dead-blow condition. 
     The invention also provides a method of at least partially offsetting an inertial event in a firing assembly of a firearm, the method comprising: evaluating an inertial event of a buffer assembly in a firearm, the buffer assembly having a buffer body, with at least one weight moveable within an internal space of the buffer body, and a first magnet and a second magnet between which a magnetic repelling force biases the weight to an at-rest position in the internal assembly, wherein in response to the inertial event the at least one weight overcomes the bias of the magnetic repelling force to achieve a dead-blow condition to at least partially offset an effect of the inertial event, and wherein the magnetic repelling force adjusts a magnitude of an impact force arising from the dead-blow condition and establishes a delay interval between the occurrence of the inertial event and to the occurrence of the dead-blow condition; determining an impact force that is a minimizing impact force and a delay interval that is a minimizing delay interval such that the minimizing impact force and minimizing delay interval combination at least partially offset the inertial event; and adjusting properties of the components of the firearm to achieve the minimizing impact force and the minimizing delay interval combination. 
     In some embodiments, the adjusted component properties are those of the first magnet and the second magnet. In some embodiments, the adjusted component properties are those of the weight. In some embodiments, the adjusted component properties are those of the encapsulation. 
     The invention also provides a firing assembly for a firearm, the firing assembly comprising: a bolt carrier movable in a rearward stroke and a forward stroke as part of a firing and loading action of the firearm; and a buffer assembly including a buffer tube including a closed rear end, an action spring in the tube, and a buffer in the tube and engaging the action spring, the buffer including a buffer body defining an internal buffer cavity, a rear end cap covering a rear end of the buffer body, a front end cap engaged with the bolt carrier, and an internal assembly within the buffer cavity, the internal assembly comprising at least one weight and a magnet; wherein a magnetic attracting force between the magnet and the bolt carrier biases the bolt carrier and the buffer towards each other; wherein the buffer is driven in rearward and forward strokes corresponding to the rearward and forward strokes of the bolt carrier and under the influence of respective rearward motion of the bolt carrier and a forward biasing force of the action spring; wherein as a result of at least one of the rearward and forward strokes, at least one inertial event occurs; wherein during the inertial event, the magnetic attracting force biases the bolt carrier and the buffer towards each other to at least partially offset an effect of the inertial event. 
     In some embodiments, the internal assembly includes a dead-blow biasing mechanism. In some embodiments, the dead-blow biasing mechanism includes at least a second magnet. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary firearm including an embodiment of the present invention. 
         FIG. 2  is an exploded view of a lower receiver assembly of the firearm, including a buffer assembly having a buffer. 
         FIG. 3  is an exploded view of an upper receiver assembly of the firearm and a bolt carrier. 
         FIG. 4A  is a cross-sectional view of a first embodiment of the buffer in an at-rest condition. 
         FIG. 4B  is a cross-sectional view of the first embodiment of the buffer in a dead-blow condition. 
         FIG. 5A  is a cross-sectional view of a second embodiment of the buffer in an at-rest condition. 
         FIG. 5B  is a cross-sectional view of the second embodiment of the buffer in a dead-blow condition. 
         FIG. 6  is a cross-sectional view of a third embodiment of the buffer in an at-rest condition. 
         FIG. 7  is a cross-sectional view of a fourth embodiment of the buffer in an at-rest condition. 
         FIG. 8A  is a cross-sectional view of a fifth embodiment of the buffer in an at-rest condition. 
         FIG. 8B  is a cross-sectional view of the fifth embodiment of the buffer in a dead-blow condition. 
         FIG. 9A  is a cross-sectional view of a sixth embodiment of the buffer in a forward-directed dead-blow condition. 
         FIG. 9B  is a cross-sectional view of the sixth embodiment of the buffer in a rearward-directed dead-blow condition. 
         FIG. 10A  is a cross-sectional view of a seventh embodiment of the buffer in an at-rest condition. 
         FIG. 10B  is a cross-sectional view of the seventh embodiment of the buffer in a rearward-directed dead-blow condition. 
         FIG. 10C  is a cross-sectional view of the seventh embodiment of the buffer in a forward-directed dead-blow condition. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  illustrates an exemplary firearm  100  which may embody the present invention. For the purposes of this disclosure, directional and relative terms such as front, forward, rear, and rearward are used from the perspective of a firearm operator using the firearm  100  in its intended way. The illustrated firearm  100  is an AR-15 rifle and includes an upper receiver assembly  110  to which a barrel  120 , hand guard  130 , lower receiver  140 , and buttstock  160  are mounted. The components are generally conventional and well known. A buffer assembly  210  is mounted to the lower receiver  140  and extends into the buttstock  160 . 
       FIG. 2  illustrates the buffer assembly  210 , which includes a buffer tube  220 , an action spring  230 , and a buffer  240 . The buffer tube  220  includes an open front end  220   a , a closed rear end  220   b , and a longitudinally-extending internal space  220   c . The open front end  220   a  of the buffer tube  220  is mounted to the rear of the lower receiver  140  with a castle nut  250  and a receiver end plate  260 . The buffer tube  220  extends rearwardly from the lower receiver  140  into the buttstock  160 . The action spring  230  is a coil compression spring having a front end  230   a  and a rear end  230   b.    
     The buffer  240  includes a cylindrical buffer body  270 , a front end cap  280 , and a rear end cap  290 . The buffer body  270  includes a front end  270   a  and a rear end  270   b . The front end cap  280  may be threaded onto the front end  270   a  of cylindrical buffer body  270 , permanently affixed to the buffer body  270 , or integrally formed with the buffer body  270 . The front end cap  280  is of wider diameter than the buffer body  270  to define a shoulder  300 . The rear end cap  290  is made of a resilient material such as urethane to cushion the impact of the buffer  240  on the rear end  220   b  of the internal space  220   c  of the buffer tube  220  when the buffer  240  is driven rearward as part of the firearm&#39;s firing and reloading action. A retaining pin or roll pin  310  secures the rear end cap  290  to the buffer body  270 . 
     The action spring  230  and buffer  240  are inserted through the open front end  220   a  of the buffer tube  220  into the internal space  220   c . The rear end  230   b  of the action spring  230  bottoms out in and abuts against the closed rear end  220   b  of internal space  220   c  of the buffer tube  220 . The buffer body  270  is surrounded by the coils of the action spring  230 . The front end  230   a  of the action spring  230  abuts the shoulder  300  of the front end cap  280 . The action spring  230  and buffer  240  are retained in the buffer tube  220  with a buffer retaining pin  340  in the lower receiver  140 . The buffer retaining pin  340  is spring biased and can be manually deflected into the lower receiver  140  to provide clearance for insertion of the action spring  230  and buffer  240 . When released from its deflected condition, the buffer retaining pin  340  extends to trap the action spring  230  and buffer  240  in the buffer tube  220 . 
       FIG. 3  illustrates a bolt carrier  215 . The bolt carrier  215  is engaged with the front end cap  280  of the buffer  240  and reciprocates in the upper receiver  110  as part of the firing action of the firearm  100 . The bolt carrier  215  is in a battery condition when fully forward in the upper receiver  110  and locked with respect to the barrel  120 . The firearm  100  may be fired when in the battery condition, which drives a bullet out of the barrel  120  under the influence of rapidly expanding barrel gases. The barrel gases are recycled from the barrel  120  to drive the bolt carrier  215 , and thereby the buffer  240 , rearward. This can be done by either directly impinging the barrel gases rearwardly on the bolt carrier  215  or by driving a piston rearwardly under the influence of the barrel gases to strike the bolt carrier  215 . In any event, the barrel gases are the motive force for the rearward motion (called a rearward stroke) of the bolt carrier  215 . During the rearward stroke, a spent shell from the just-fired round is ejected through a side door of the upper receiver  110  and the action spring  230  is compressed in the buffer tube  220 . The rearward stroke ends when the rear end cap  290  bottoms out against the rear end  220   b  of the buffer tube  220 . 
     A forward stroke commences under the influence of the action spring  230 . During the forward stroke, the action spring  230  drives the buffer  240  and bolt carrier  215  forward. The bolt carrier  215  collects a new round from a magazine under the upper receiver  110  and drives the new round into the battery condition. The forward stroke ends when the bolt carrier  215  is in the battery condition, ready to fire the new round. 
     The present invention relates to a dead-blow mechanism inside the buffer body  270 , and more specifically to a magnetic dead-blow biasing mechanism  460  which is part of the dead-blow mechanism. As will be discussed in more detail below, the dead-blow mechanism has two conditions: an at-rest condition and a dead-blow condition. The dead-blow biasing mechanism  460  biases the dead-blow mechanism into the at-rest condition. The dead-blow condition is achieved by overcoming the biasing force of the dead-blow biasing mechanism  460  in response to an inertial event. The purposes of the dead-blow mechanism in the buffer body  270  is to reduce bounce of the bolt carrier  215  or slow down acceleration of the bolt carrier  215  at the beginning or end of the rearward stroke or the beginning or end of the forward stroke, when inertial events occur. Reducing bounce and slowing down acceleration can improve shooting accuracy and optimize the timing of the firing action, as will be described in more detail below. 
       FIGS. 4A-10C  illustrate various configurations (referred to as “embodiments” herein) of an internal assembly  410 ,  510 ,  610 ,  710 ,  810 ,  910 ,  1010  of the buffer  240 . The internal assembly  410 ,  510 ,  610 ,  710 ,  910 ,  1010  is received in a buffer cavity  270   c  inside the buffer body  270 . Each internal assembly  410 ,  510 ,  610 ,  710 ,  810 ,  910 ,  1010  includes a plurality of conventional masses (referred to as “weights” herein)  420 ,  421  and conventional resilient spacers  430 . In the illustrated embodiments, the spacers  430  are rubber. The plurality of conventional weights  420 ,  421  includes a forwardmost weight ( 421   f  or  420   f ) and a rearmost weight ( 421   r  or  420   r ). Although the illustrated embodiment includes four identically-dimensioned weights  420 ,  421 , it will be understood for the purposes of these embodiments that there may be more or fewer weights having different dimensions depending on the particular application and desired performance of the buffer  240 . The weights  420 ,  421  may also be made of different materials having different densities to arrive at the desired functionality for the particular application. Although the weights  420 ,  421  may be made of any ferrous or non-ferrous material, preferably the weights  420 ,  421  are made of a material that is as dense as, and that weighs an equal amount as or more than, stainless steel. In the illustrated embodiments, the weights  420  are preferably made of tungsten, or of another high-density metal material, and the weights  421  are preferably made of carbon steel, stainless steel, or some other material with similar properties. The weights  420  have planar, flat forward and rearward ends. The spacers  430  are positioned between the flat ends of adjacent weights  420 ,  421 . 
     The illustrated embodiments also include a magnetic dead-blow biasing mechanism  460  in the form of a first magnet  450   a  and a second magnet  450   b  (the embodiment illustrated in  FIG. 9  may or may not include a dead-blow biasing mechanism  460 ). In each embodiment, like poles (i.e., north or south) of the first and second magnets  450   a ,  450   b  face each other to create a repelling biasing force. Each embodiment has an at-rest condition which is the condition into which the internal assemblies  410 ,  510 ,  610 ,  710 ,  810 ,  910 ,  1010  (or more specifically the position into which the weights  420 ,  421 ) are biased by the magnetic dead-blow biasing mechanism  460 . Each embodiment also has a dead-blow condition in which the biasing force of the dead-blow biasing mechanism  460  has been overcome by inertia forces that bring the magnets  450   a ,  450   b  into contact or into close proximity. The dead-blow biasing mechanism  460  resets the internal assemblies  410 ,  510 ,  610 ,  710 ,  810 ,  910 ,  1010  to the at-rest condition after a sufficient recovery time has passed following the occurrence of the dead-blow condition. 
     As will be explained below, the magnetic dead-blow biasing mechanism  460  can be configured to achieve the dead-blow condition at the end of the rearward stroke, the beginning of the rearward stroke, or at both the beginning and end of the rearward stroke. The magnetic dead-blow biasing mechanism  460  might be set up to achieve the dead-blow condition at the end of the rearward stroke when the action spring  230  is overly stiff or overly preloaded. In this situation, referred to as “oversprung,” the action spring  230  may cause the buffer  240  and bolt carrier  215  to transition from the rearward stroke to the forward stroke too quickly, which can cause the cycle of the action to operate too quickly. If the cycle of the action is too quick, the next round may not be properly gathered and loaded into battery condition by the bolt carrier  215 . The magnetic dead-blow biasing mechanism  460  might be setup to achieve the dead-blow condition at the beginning of the rearward stroke when too much barrel gas is used to initiate the rearward stroke. In this situation, referred to as “overgassed,” the bolt carrier  215  jolts rearwardly too suddenly with the buffer  240 , resulting in the bolt carrier  215  and the buffer  240  accelerating so quickly in the rearward direction that the bolt carrier  215  and the buffer  240  rebound off the rear end  220   b  of the buffer tube  220 . The magnetic dead-blow biasing mechanism  460  may be set up to achieve the dead-blow condition at both the end and beginning of the rearward stroke when the action is slightly oversprung and overgassed. 
     One factor that must be considered when designing the magnetic dead-blow biasing mechanism  460  is a delay interval. The delay interval is the time it is expected to take for the weights  420 ,  421  to overcome the bias of the magnetic dead-blow biasing mechanism  460  and come to a dead-blow condition after an inertial event has occurred. Inertial events include the buffer  240  suddenly ceasing movement after being in motion and when the buffer  240  suddenly goes into motion from an at-rest position. Examples of inertial events arising from the buffer  240  suddenly ceasing movement include: (i) the buffer  240  striking the rear end  220   b  of the buffer tube  220  at the end of the rearward stroke; (ii) the buffer  240  striking the bolt carrier  215  during an initial period of the forward stroke if the buffer  240  and bolt carrier  215  become separated; and (iii) the bolt carrier  215  reaching the battery condition at the end of the forward stroke. Examples of inertial events arising from the buffer  240  suddenly going into motion include: (i) the start of the rearward stroke under the influence of barrel gases (by direct impingement or through a piston); and (ii) the start of the forward stroke under the influence of the action spring  230 . The delay interval should be set to properly time the impact of the weights  420 ,  421  in the buffer  240  to offset a rebound  240  of the buffer  240  or to slow down an acceleration of the buffer  240 . 
     An impact force provided by the weights  420 ,  421  after a delay interval reduces, minimizes, or eliminates bounce or rebound of the buffer  240  or slows down an acceleration of the buffer  240  after an inertial event. This effect is similar to the effect of a dead-blow hammer. For convenience, the dead-blow hammer effect just described is encompassed in the shorthand phrase “offset an inertial event.” To achieve the dead-blow hammer effect to offset an inertial event of the buffer  240  for desirable firearm  100  operation, the delay interval and the impact force must be fine-tuned. The proper combination of delay interval and impact force results in desirable operation of the firearm, and the delay interval and impact force that create this combination can be referred to as minimizing delay interval and minimizing impact force respectively. If these variables are not fine-tuned, the inertial event of the buffer  240  will not be offset. 
     For example, if the delay interval is too short, the weights  420 ,  421  will cause the impact force too soon after an inertial event. In this situation, the impact force does not create a dead-blow effect, but instead amplifies bounce or fails to slow down acceleration. Alternatively, if the delay interval is too long, the weights  420 ,  421  will cause the impact force too late after the inertial event. In this scenario, the impact force occurs after the buffer  240  has already bounced and the buffer  240  bounces for a second time during the same stroke. In addition, if the impact force provided by the front and rear weights is too small it will not sufficiently cancel out the bounce of the buffer. If the impact force of the weights is too great it will more than cancel out the bounce of the buffer and the excess impact force will cause bounce. 
     To fine tune the delay interval and impact force such that the inertial event is at least partially offset, the inertial event must be evaluated for relevant parameters. Relevant parameters include at least the acceleration of the buffer  240  and the bolt carrier  215 , as well as the length of time over which the inertial event takes place. Using these parameters, the required minimizing delay interval and minimizing impact force for offsetting the inertial event can be determined. The properties of components of the firearm can then be adjusted so that the firearm assembly operates with the minimizing delay interval and the minimizing impact force required for desirable firearm operation. 
     The delay interval and the impact force are functions of multiple factors, including at least: the mass of the weights  420 ,  421 ; the travel distance between at-rest condition and dead-blow condition; friction; and strength (e.g., magnitude) of the magnetic force of the magnets  450   a ,  450   b . The magnitude of the magnetic force of the magnets  450   a ,  450   b  is generally a function of: (i) the permeability of space between the first and second magnets  450   a ,  450   b ; (ii) the magnetic field strength of the first and second magnets  450   a ,  450   b ; (iii) a length of a face-to-face distance between the first and second magnets  450   a ,  450   b ; and (iv) geometry of the first and second magnets  450   a ,  450   b.    
     In all the embodiments, the material of an encapsulation  440  may be changed, in the embodiment illustrated in  FIGS. 4A and 4B , the material of the rear end cap  290  may be changed, in the embodiment illustrated in  FIGS. 5A-8C , the material of the spacers  430  may be changed, and in the embodiment illustrated in  FIG. 7 , the material of the buffer body  270  may be changed to fine-tune permeability of space and thereby the magnetic force. A combination of changing these materials may be used as well. Other methods of altering the permeability of space between the first and second magnets  450   a ,  450   b  include introducing various gases into the buffer cavity  270   c  of the buffer body  270  to change the permeability of space of air in the buffer cavity  270   c . Also, changing the thicknesses of any of the components between the first and second magnets  450   a ,  450   b  will alter the magnetic force, since the total permeability of space between the first is a weighted ratio of the permeability of space of all of the components within the space between the first and second magnets  450   a ,  450   b . Altering the types of the first and second magnets  450   a ,  450   b  may also change the magnetic field strength of the first and second magnets  450   a ,  450   b  to alter the magnetic force, since magnetic field strength is an intrinsic material property. 
     The geometry of the first and second magnets  450   a ,  450   b  may also be changed to alter the magnetic force. Also, the face-to-face distance between the first and second magnets  450   a ,  450   b  at the rearward-inertia condition and the forward-inertia condition may be altered by changing the length of some or all of the weights  420 ,  421 , the length of some or all of the spacers  430 , the thickness of the encapsulation  440 , and/or the distance that the rear end cap  290  extends into the buffer cavity  270   c  of the buffer  240 . Altering the face-to-face distance adjusts both the initial starting magnetic force exerted between the first and second magnets  450   a ,  450   b , as well as the way in which the magnetic force is exerted between the first and second magnets  450   a ,  450   b  over time. Altering any of the variables of which the magnetic force is a function, either alone or in combination, may change the magnitude of the magnetic force. By changing the magnitude of the magnetic force, the delay interval and the impact force are also changed, and may be adjusted to achieve the desired minimizing delay interval and minimizing impact force. 
     Turning now to the illustrated embodiments,  FIGS. 4A and 4B  illustrate an internal assembly  410  designed to specifically address an overgassed firearm  100 . The illustrated internal assembly  410  includes a first magnet  450   a  disposed on a rear face of the rearmost weight  420   r , and a second magnet  450   b  held entirely within (e.g., encapsulated in) the rear end cap  290 . In some embodiments, a portion of the second magnet  450   b  may be exposed to the buffer cavity  270   c  rather than completely contained within the end cap  290 . The magnets  450   a ,  450   b  are arranged such that their ends of a same polarity (north or south) face each other and the magnets  450   a  and  450   b  exert repellent magnetic forces on each other. Preferably, the encapsulation material  440  is injection molded nylon, copper or nickel plating, or hardened epoxy dip, but other materials with similar properties may be used.  FIG. 4A  illustrates the internal assembly  410  in the at-rest condition and  FIG. 4B  illustrates the internal assembly  410  in the dead-blow condition following an inertial event and the delay interval. 
     The internal assembly  410  operates as follows. The internal assembly  410  is in the at-rest condition ( FIG. 4A ) when the bolt carrier  215  is in the battery condition (i.e., full forward). The rearward stroke starts under the influence of barrel gases (by direct impingement or through a piston), which is an inertial event causing the buffer body  270  to jolt rearwardly. The impact force arising from this inertial event are absorbed by the resilient spacers  430 . When the buffer  240  bottoms out in the buffer tube  220 , another inertial event occurs and the weights  420 ,  421  slam into the rear end cap  290  ( FIG. 4B ) to achieve the dead-blow condition. The dead-blow condition offsets the inertial event to reduces bounce of the bolt carrier  215  and the buffer  240  off the rear end  220   b  of the buffer tube  220  and makes the buffer  240  pause before starting the forward stroke. The dead-blow biasing mechanism  460  resets the internal assembly  410  to the at-rest condition ( FIG. 4A ) while the buffer  240  pauses. Then the action spring  230  drives the buffer  240  forward into the battery condition. If the force of the action spring  230  is sufficiently quick and forceful another inertial event may occur to again achieve the dead-blow condition, followed by the dead-blow mechanism  460  resetting the internal assembly  410  to the at-rest condition. Otherwise the internal assembly  410  remains in the at-rest condition for the full forward stroke. The resilient spacers  430  absorb impact force at the end of the forward stroke when the buffer  240  achieves battery condition. 
       FIGS. 5A and 5B  illustrate a second configuration of an internal assembly  610  of the buffer  240  designed to specifically address an oversprung firearm  100 . The internal assembly  610  has all the same components as the first embodiment  410 , and differs only in the configuration. In the internal assembly  610 , the first magnet  450   a  is disposed on a front face of the forwardmost weight  420   f , and the second magnet  450   b  disposed within the front end cap  280  such that a portion of the second magnet  450   b  is exposed to the buffer cavity  270   c . In some embodiments, the second magnet  450   b  may be held entirely within (i.e., completely encapsulated) the front end cap  280 . The forwardmost weight  420   f  and the second magnet  450   b  are encapsulated together within an encapsulation  440 .  FIG. 5A  illustrates the internal assembly  610  in an at-rest condition and  FIG. 5B  illustrates the internal assembly  610  in the dead-blow condition following an inertial event and the delay interval. 
     The internal assembly  610  operates as follows. The internal assembly  610  is in the at-rest condition ( FIG. 4A ) when the bolt carrier  215  is in the battery condition (i.e., full forward). The rearward stroke starts under the influence of barrel gases (by direct impingement or through a piston). If the influence of the barrel gases is sufficiently quick and forceful an inertial event may occur to achieve the dead-blow condition, followed by the dead-blow mechanism  460  resetting the internal assembly  610  to the at-rest condition. Otherwise the internal assembly  610  remains in the at-rest condition for the full rearward stroke. The resilient spacers  430  absorb impact force at the end of the rearward stroke when the buffer  240  bottoms out in the buffer tube  220 . The forward stroke then starts under the influence of the action spring  230 , which is an inertial event causing the buffer body  270  to jolt forwardly. The impact force arising from this inertial event are absorbed by the resilient spacers  430 . When the buffer  240  tops out into battery condition, another inertial event occurs and the weights  420 ,  421  slam into the front end cap  280  ( FIG. 4B ) to achieve the dead-blow condition. The dead-blow condition offsets the inertial event to reduce bounce of the buffer  240  off the rear end of the bolt carrier  215 . The dead-blow biasing mechanism  460  resets the internal assembly  410  to the at-rest condition ( FIG. 4A ) before the next rearward stroke begins. 
     In the embodiments illustrated in  FIGS. 4A-5B , during an inertial event at the end of a rearward stroke or a forward stroke, the internal assembly  410 ,  510  within the buffer  240  offsets an inertial event. At the end of a forward stroke (i.e., a forward-directed inertial event), the internal assembly  410 ,  510  prevents the buffer  240  from bouncing off of the bolt carrier  215 . The bolt carrier  215  cannot bounce at the end of a forward stroke because the bolt carrier  215  is locked into the battery position. At the end of a rearward stroke (i.e., a rearward-directed inertial event), the internal assembly similarly prevents the buffer  240  from bouncing off of the rear end  220   b  of the buffer tube  220 . However, the bolt carrier  215  may bounce off the buffer  240  at the end of a rearward stroke if the dead-blow mechanism is not properly tuned to the combined masses of the buffer  240  and bolt carrier  215 , which is difficult to accomplish in a dynamic rapidly-moving system such as a firearm. 
       FIG. 6  illustrates a third configuration or embodiment of an internal assembly  710  of the buffer  240  which addresses both an oversprung firearm and bounce of the bolt carrier  215  off the buffer  240  at the end of a rearward stroke. The internal assembly  710  is most similar to the second embodiment  610  and operates in an similar manner. The embodiment illustrated in  FIG. 6  differs from the embodiment illustrated in  FIGS. 5A and 5B  in that the first magnet  450   b  of the third embodiment disposed within the front cap  280  is thicker and therefore more powerful than the magnet  450   b  of the second embodiment. The thicker and more powerful magnet  450   b  of the third embodiment has an additional advantage in that a front face of the magnet  450   b  may exert a large enough magnetic attracting force on the bolt carrier  215  to bias the bolt carrier  215  and buffer body  240  towards each other (i.e., magnetically couple the bolt carrier  215  and buffer body  240  so that the two components effectively move together as a single component). 
     The bolt carrier  215  therefore remains biased towards the front end cap  280  of the buffer  240  over the entire course of a firing action of a firearm. When an inertial event occurs at the end of a rearward stroke, the bolt carrier  215  remains biased towards (magnetically coupled to) the buffer  240  such that any bounce not offset by the resiliency of the rear end cap  290  and resilient spacers  430  in the buffer  240  is overcome by the magnetic attraction to further reduce or eliminate bounce of the bolt carrier  215  off of the buffer  240  (i.e., physical separation of the bolt carrier  215  from contact with the buffer  240 ). Additionally, the bolt carrier  215  remains biased towards the buffer  240  during an inertial event at the end of a forward stroke. The magnetic attracting force acts together with the weights  420 ,  421  coming to a dead-blow condition to bias the buffer  240  towards the bolt carrier  215  to further offset the inertial event and further reduce the bounce of the buffer  240  off of the bolt carrier  215 . In some embodiments, the magnetic attracting force between the bolt carrier  215  and buffer  240  may be sufficiently strong to maintain engagement between the bolt carrier  215  and the buffer  240  during the entire firing and reloading action of the firearm. Additionally, the strength of the magnetic dead-blow biasing mechanism  460  enables a resilient spacers  430  to be positioned in the space between the two magnets  450   a ,  450   b  to reduce noise. 
       FIG. 7  illustrates a fourth embodiment of an internal assembly  810  of the buffer  240 . The internal assembly  810  is most similar to the third embodiment  710  and operates in an similar manner. The embodiment illustrated in  FIG. 7  differs from the embodiment illustrated in  FIG. 6  in that a portion of the magnet  450   b  is exposed to the internal space  225  of the upper receiver  110 . The exposed portion of the magnet  450   b  has the additional advantage in that, the magnet  450   b  of the fourth embodiment exerts a stronger attractive magnetic force on the bolt carrier  215  than the magnet  450   a  of the third embodiment. By exerting a stronger force between the bolt carrier  215  and the front end cap  280 , the bolt carrier  215  and the buffer  240  are more effectively hindered from bouncing away from each other, further increasing the accuracy of the firearm  100 . 
       FIGS. 8A and 8B  illustrate a fifth configuration of an internal assembly  910  of the buffer  240 . The internal assembly  910  is most similar to the first embodiment  410 . The dead-blow biasing mechanism  460  operates in an identical manner to that of the first embodiment  410  to address an overgassed firearm, but the embodiment illustrated in  FIGS. 8A and 8B  also includes a third magnet  450   c . The third magnet  450   c  operates in a similar manner to second magnet  450   b  of the embodiments illustrated in  FIGS. 6 and 7 , to bias the bolt carrier  215  and the buffer  240  towards each other. The embodiment illustrated in  FIGS. 8A and 8B  has the added advantage that the third magnet  450   c  has a larger radius than the second magnet  450   b  of the embodiments illustrated in  FIGS. 6 and 7 . Specifically, the radius of the third magnet  450   c  is larger than a radius of the buffer cavity  270   c . The front end cap  280  in this embodiment might be threaded onto the front end of the buffer body  270 , with the third magnet  450   c  captured between the front end cap  280  and the front end of the buffer body  270 . The third magnet  450   c  of the fifth embodiment is therefore more powerful than the second magnet  450   b  of the third and fourth embodiments, and exerts a stronger magnetic attracting force on the bolt carrier  215 . This stronger magnetic attracting force further offsets the inertial event at the end of a rearward stroke or a forwards stroke, and thereby further prevents the bolt carrier  215  and the buffer  240  from bouncing off one another. 
       FIGS. 9A and 9B  illustrate a sixth configuration of an internal assembly  1010  of the buffer  240 . The internal assembly  1010  is most similar to the fifth embodiment  910 , as the internal assembly  1010  includes a magnet  450   c  with a radius larger than the buffer cavity  270   c . The magnet  450   c  operates in an identical manner to that of the embodiment illustrated in  FIGS. 8A and 8B , to bias the bolt carrier  215  and the buffer  240  towards each other, and to thereby prevent the bolt carrier  215  and the buffer  240  from bouncing off one another. The internal assembly  1010  of the sixth embodiment illustrated in  FIG. 9  however does not include a dead-blow biasing member  460  including a first magnet  450   a  and a second magnet  450   b . In the embodiment illustrated in  FIG. 9 , the internal assembly does not include a dead-blow biasing member  460  at all. In other embodiments, the internal assembly  1010  may include a dead-blow biasing member  460  that is a spring or another dead-blow biasing mechanism known in the art. 
     The internal assembly  1010  operates as follows. The internal assembly  1010  is in an at-rest condition ( FIG. 9A ) when the bolt carrier  215  is in the battery condition. To begin a firing action, the rearward stroke occurs. If the rearward stroke is forceful enough, an inertial event may occur to achieve a dead-blow condition ( FIG. 9B ), followed by the spacers  430  absorbing impact force at the end of the rearward stroke when the buffer  240  bottoms out. Otherwise the internal assembly  1010  remains in the at-rest condition for the full rearward stroke until the buffer  240  bottoms out. When the buffer  240  bottoms out, another inertial event occurs and the weights  420 ,  421  slam into the rear end cap  290  to achieve a dead-blow condition ( FIG. 9B ). The dead-blow condition offsets the inertial event to reduce bounce of the buffer  240  off the buffer tube  220 . Bounce of the bolt carrier  215  off of the buffer  240  at the end of a rearward stroke is also reduced by the magnet  450   c , which exerts a magnetic attracting force on the bolt carrier  215  to bias the bolt carrier  215  towards the buffer  240 . At the conclusion of the rearward stroke, the dead-blow condition of the rearward stroke ( FIG. 9B ) becomes the at-rest condition of the forward stroke. The forward stroke then starts, and if the forward stroke is forceful enough, an inertial event may occur to achieve the dead-blow condition of the forward stroke ( FIG. 10B ). The spacers  430  handle the impact force in this instance. Otherwise, the internal assembly remains in the at-rest condition for the full forward stroke until the buffer  240  tops out and creates another inertial event. The weights  420 ,  421  slam into the front end cap  280  to achieve the dead-blow condition, offsetting the inertial event and preventing bounce of the buffer  240  off of the bolt carrier  215 . Bounce of the buffer  240  off of the bolt carrier  215  at the end of a forward stroke is also reduced by the magnet  450   c , which exerts a magnetic attracting force on the buffer  240  to bias the buffer  240  towards the bolt carrier  215 . At the conclusion of the forward stroke, the dead-blow condition of the forward stroke ( FIG. 9A ) becomes the at-rest condition of the rearward stroke as the next rearward stroke begins. 
       FIGS. 10A, 10B, and 10C  illustrate a seventh embodiment of an internal assembly  510  of the buffer  240 . The internal assembly  510  is similar to the first embodiment  410  but the first and second magnets  450   a ,  450   b  are disposed on adjacent faces of adjacent inner weights  420 . An at-rest condition of the internal assembly  510  is illustrated in  FIG. 10A  and first and second dead-blow conditions of the internal assembly  510 , following respective inertial events and delay intervals, are illustrated in  FIGS. 10B and 10C . 
     Turning to  FIG. 10B , at the end of the rearward stroke, an inertial event occurs which causes the front weights  420 ,  421   f  to overcome the magnetic biasing mechanism  460  and slide into contact with the rear weights  420 ,  421   r  with an impact force that is partially cushioned by the resilient spacers  430  to reduce noise and provide compliance. The impact force is of sufficient magnitude and of proper timing to reduce bounce of the buffer  240  and cause the buffer  240  to pause before starting the forward stroke. During the pause, the magnetic biasing mechanism  460  returns the internal assembly  510  to the at-rest condition illustrated in  FIG. 10A . 
     With reference now to  FIG. 10C , at the end of the forward stroke, an inertial event occurs which causes the rear weights  420 ,  421   r  to overcome the magnetic biasing mechanism  460  and slide into contact with the forward weights  420 ,  421   f  with an impact force that is partially cushioned by the resilient spacers  430  to reduce noise and provide compliance. The impact force is of sufficient magnitude and of proper timing to reduce bounce of the buffer  240  off the bolt carrier  215 . Before the rearward stroke begins, the magnetic biasing mechanism  460  returns the internal assembly  510  to the at-rest condition illustrated in  FIG. 10A . 
     Depending on the magnitude and acceleration of the beginning of the forward and rearward strokes, the biasing force of the magnetic biasing mechanism  460  can be overcome to move the weights  420 ,  421  into the first and second dead-blow conditions of  FIGS. 10B and 10C , respectively. 
     Because only half of the plurality of weights  420 ,  421  in the embodiments of  FIGS. 10A-10C  are providing the impact force to reduce the bounce of the buffer  240  as compared to the embodiments of  FIGS. 4A-9B , the impact forces provided in the embodiments of  FIGS. 10A-10C  are generally not as large as those provided by the embodiments of  4 A- 9 . The properties of the weights  420 ,  421  (such as density, volume, etc.) can be altered so that the weights  420 ,  421  can provide the required impact forces for desirable operation of the firearm  100 . 
     Thus, the invention provides, among other things, a buffer assembly that includes at least one magnet that offsets an inertial event that occurs during the firing action of a firearm. The magnet thereby reduces, minimizes, or eliminates bounce or rebound of the buffer at the rear end of the buffer tube and/or at the bolt carrier. Various features and advantages of the invention are set forth in the following claims.