Patent Publication Number: US-2011061523-A1

Title: Semi Bolt Receiver Assembly for assembly with a Semi Automatic Rifle Base

Description:
Related Application/Claim of Priority 
     This application is related to and claims priority from U.S. provisional application Ser. No. 61/276,629, filed Sep. 15, 2009, entitled “Semi bolt action conversion adaptor for AR 15 rifle” which provisional application is incorporated herein by reference 
    
    
     INTRODUCTION, BACKGROUND AND SUMMARY OF THE PRESENT INVENTION 
     The present invention relates to a new and useful structure, referred to herein as a “semi bolt receiver assembly” that is designed to be coupled with semi automatic rifle base, e.g. the lower portion (also referred to as a lower receiver) of a rifle of the modular type which is well known in connection with a rifle known as the AR 15. The type of semi automatic rifle base with which the semi bolt receiver assembly of the present invention is particularly useful would typically comprise a buttstock and pistol grip configured for semi automatic operation, such that the buttstock has a buffer spring that is compressed by movement of a bolt and carrier assembly against a buffer when the rifle is being discharged or unloading a spent round and causes the buffer to act on a bolt carrier assembly (e.g. in the manner of a semi automatic rifle) when the rifle is being charged or loaded. 
     The principles of the present invention are described herein in connection with conversion of a semi automatic rifle base (e.g. an AR15 semi automatic rifle base) to semi bolt-action operation with the apparatus described herein, and from that description the manner in which the principles of the present invention can be used to convert similar types of rifle base, (e.g. AR 10 or SR 25 rifles) or create new rifles in accordance with those principles, will be apparent to those in the art. In addition, the principles of the present invention are particularly useful to produce an upper receiver assembly that can be assembled with a rifle based that is substantially conformable to the standards of existing AR 15/M16 rifle lower receivers. 
     In applying the principles of the present invention to a semi automatic rifle base such as an AR 15 rifle, the purpose of the invention includes: 
     1) improving the accuracy of the rifle by converting the gas operating system to manual operation; 
     2) retaining a cartridge loading speed advantage over convention bolt action rifles; 
     3) eliminating the action fouling due to the gas operating system of the semi automatic AR 15 rifle; and 
     4) improving the ability to manipulate the bolt with the least movement and effort. 
     The AR15 Rifle is one of the most versatile and affordable rifle designs ever conceived and certainly the most modified and adapted beyond its intended military use. In recent years it has become the most widely used target rifle in certain competitive disciplines and new dedicated variants appear frequently. 
     The rifle is divided into an upper and lower half (Exhibits A1, A2). The lower half, connects to a buttstock, and contains the pistol grip, the trigger mechanism and holds the ammunition. It is the registered part of the rifle. The upper half, to which this invention pertains, contains the bolt and carrier assembly, the barrel, sights and special purpose attachments. It can be configured in many ways. Because of its modular design it is possible to have one lower half and many different upper halves (sometimes called variants) each dedicated to a different type of shooting or purpose because each will mate to the lower half. The invention proposed herein was inspired primarily by a desire to improve the performance of the rifle in the target shooting disciplines but should have diverse appeal. It should be considered a new variant because it has a dedicated design and function that is distinctly different from any existing variants or any known rifles known to applicant. 
     If the AR15 Rifle has a drawback, in the sport of target shooting, it is the gas operated self-loading system that employs parts that move during the shot process. It is an undesirable characteristic that can affect accuracy and many top competitors prefer to use a traditional or specialized bolt action rifles in long-range events, bench rest competition, or varmint hunting; all of which demand extreme accuracy. The bolt-action rifle operates with a closed bolt throughout the firing process and causes no disturbance to the rifle when it is fired. However, despite having an edge in accuracy the bolt action rifle has its own drawbacks. For example, in NRA “Match Rifle” competition there are two separate rapid-fire stages in the match that are conducted at different ranges and from different positions. Many shooters have difficulty firing all the required shots accurately due to the time it takes to manually operate the bolt; which must be raised to unlock the bolt, pulled to extract the spent cartridge, pushed in order to extract a cartridge from the magazine and chamber it, and lowered in order to lock the bolt. Sometimes the shooter must raise his head off the stock to avoid the retracting bolt. In the prone position it is sometimes necessary to lift ones arm from the shooting mat, in order to operate the bolt. The more expensive bolt action competition rifles incorporate features designed to overcome these drawbacks (in a manner different than the present invention) but most shooters cannot afford them. All of these circumstances cause the “position” of the shooter to break down. At these short and middle range events, which are fired at 200 to 300 yards the self-loading AR15 rifle enjoys an advantage because the shooter does not have to manipulate a bolt. The same rifle must be used across the entire course of fire. 
     When the match moves back to the 600-yard slow fire stage the bolt-action rifle assumes an advantage because there are no moving parts during the shot process. The scores at this stage generally determine the winner of the match. With the recent offering of improved cartridges and calibers for the AR15 the bolt-action does not enjoy the complete dominance that it once had at long range, but it is often preferred. 
     The invention described herein seeks to address the issue of accuracy and retain most of the speed advantage enjoyed by the AR15 with a semi bolt-action configuration. It also has the added benefit of a much cleaner action with less wear and requires less lubrication and maintenance by way of eliminating the gas operating system which fouls the action. It also makes it ergonomically feasible to shoot accurately in timed shooting events that, until now, have been impractical with other conversions. The application is intended primarily for rifles that would normally employ an AR15 A3 style flattop upper receiver which often requires the use of a scope, as in bench rest shooting, or sophisticated iron sights as in NRA Match Rifle competition. It will easily adapt to other disciplines as well. 
     In accordance with the present invention, a semi bolt receiver assembly is configured for assembly with a rifle base that has a buttstock and pistol grip configured for semi automatic operation. The semi bolt receiver assembly includes a bolt and carrier assembly, and a manually operable handle is coupled with the bolt and carrier assembly in a manner that enables the bolt and carrier assembly to be manipulated by a shooter to charge the rifle (i) while the shooter is maintaining a shooting position and (ii) without removing the shooter&#39;s hand from the pistol grip. Preferably, the handle and bolt and carrier assembly are coupled and configured in a manner that enables the operation of the manually operable handle in charging the rifle to be substantially a straight pull action, while the shooter is maintaining an undisturbed shooting position. 
     The concept of a rifle base that is configured for semi automatic operation means that the rifle base has an attached buttstock and pistol grip configured for semi automatic operation means, in that the buttstock has a buffer spring that is compressed when the rifle is being discharged or unloaded and acts on a buffer to move the bolt carrier assembly in the manner of a semi automatic rifle when the rifle is being charged or loaded. 
     In a preferred embodiment, the manually operable handle is coupled with an adaptor base in a manner that enables the length of pull of the adjustable handle to be selectively adjusted over a predetermined range. In addition, the handle is coupled with the adaptor base in a manner that the handle extends at an angle to the bolt and carrier assembly and allows the handle to be selectively manipulated to adjust the angle at which the handle is oriented relative to the bolt and carrier assembly. The connection between the handle and the bolt and carrier assembly is preferably configured in a manner that enables the operation of the manually operable handle in charging the rifle to be substantially a straight pull action by a shooter, along a side of the receiver, in a convenient orientation to be grasped by a shooter&#39;s hand on that side of the receiver. 
     Also, the bolt and carrier assembly includes a bolt carrier with a substantially cylindrical configuration, and the adaptor base is connected with the bolt carrier by one or more fasteners that extend from the adaptor base through the top of the cylindrical bolt carrier and directs forces applied to the fastener from the top of the cylindrical bolt carrier downward along a line of action extending through the center of the cylindrical bolt carrier. Thus, the line of action of forces on the bolt and carrier assembly is through a relatively strong section of the bolt and carrier assembly, which is designed to minimize the risk of breakage of components when the rifle is being manipulated and fired. 
     Thus, a rifle with a semi bolt receiver assembly configured according to the principles of the present invention, is designed to enable a shooter to recharge the bolt and carrier assembly while maintaining a shooting position and without removing the shooter&#39;s hand from the pistol grip. This enables the shooter to have the accuracy normally provided by a bolt action rifle, and the speed of firing that is normally associated with a semi automatic rifle such as the AR 15. The principles of the present invention are particularly useful in configuring a semi bolt receiver assembly that can be assembled with a rifle base or lower receiver that is substantially conformable to the standards of existing AR15/M16 rifles. 
     These and other features of the present invention will become further apparent from the following detailed description, and the accompanying drawings and exhibits. 
    
    
     
       Brief Description of the Drawings and Exhibits 
         FIG. 1  is a schematic illustration of a shooter in a firing position with a rifle having semi bolt receiver assembly, according to the principles of the present invention; 
         FIG. 2  is an enlarged, schematic illustration of a portion of the rifle having the semi bolt receiver assembly according to the principles of the present invention; 
         FIG. 3  is an exploded view of components forming the semi bolt receiver assembly, according to the principles of the present invention; 
         FIG. 4  is a schematic illustration of the semi bolt receiver assembly according to the principles of the present invention, in one of its operational positions; 
         FIG. 5  is a side view of a modified configuration of an adaptor base, handle and handle mount, for a semi bolt receiver assembly, according to the principles of the present invention; 
         FIG. 6  is a top view of the modified configuration of  FIG. 5 ; 
         FIG. 7  is a side view of a portion of the receiver, for the modified configuration of  FIG. 5 ; and 
         FIG. 8  is a rear view of the modified configuration of  FIG. 5 . 
       Exhibit A1 is an exploded view of the primary components of an AR 15 rifle, Exhibit A2 is a detailed exploded view, and parts list for an AR 15 rifle, Exhibit A3 illustrates how when the principles of the present invention are used to modify an existing AR 15 rifle, the adaptor base of the present invention prevents the bolt from closing if the gas tube of the AR 15 is not removed, and 
       Exhibits B-D are views of a shooter operating a rifle with an AR 15 rifle base, and a semi bolt receiver assembly configured according to the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As described above, the present invention relates to a new and useful structure, referred to herein as a “semi bolt receiver assembly” that is designed to be coupled with a modular type rifle base, which is well known in connection with a rifle known as the AR 15. In a typical AR 15 rifle, the primary components are a magazine  1 , bolt carrier assembly  3 , charging handle  4 , upper receiver and barrel assembly  5 , and lower receiver and buttstock assembly  6  (see Exhibit A1). The semi bolt receiver assembly of the present invention would replace the upper receiver and barrel assembly. The coupling between the semi bolt receiver assembly of the present invention and the lower receiver and buttstock assembly  6  would typically comprise takedown or pivot pins that are shown at  77  and  61  in Exhibit A2. 
     The principles of the present invention are described herein in connection with conversion of a typical AR15 semi automatic rifle to semi bolt-action operation with the semi bolt receiver assembly described herein. Also, Exhibit A2 shows an exploded view and parts list for an AR 15 rifle, and wherever possible in this description, where a component that is described herein is essentially the same as the part of Exhibit A1 or Exhibit A2, applicant has sought to retain the numbering scheme of Exhibits A1 and A2. Where a component is either not shown in Exhibits A1 or A2, or is different from a component of those exhibits, on account of that component being configured in accordance with the principles of the present invention, applicant has adopted a numbering scheme different from the parts lists of Exhibits A1 and A2. In addition, in the course of this detailed description, applicant has described existing rifles known to applicant and the manner in which a rifle with the applicant&#39;s semi bolt receiver assembly both differs from those existing rifles, and is also believed to provide advantages in relation to those rifles. From that description the manner in which the principles of the present invention can be used to convert rifles similar to the AR 15, or create new rifles in accordance with those principles, will be apparent to those in the art. 
     According to the present invention a semi bolt receiver assembly  100  ( FIG. 3 ) is configured for assembly with a rifle base  102  that has a buttstock  104  (of conventional design as shown as part of the lower receiver and Buttstock assembly  6  shown in Exhibit A1) and pistol grip  74  (also of conventional design, see e.g. Exhibit A2). The rifle base  102  has a trigger  65 , a buffer spring  41  and a buffer  42  (piston), that are of conventional design (see e.g. Exhibit A2) and is configured for semi automatic operation, in the sense that when the rifle discharges a spent cartridge, by pulling the charging handle that is described herein, the buffer spring  41  is compressed, and when the charging handle  120  (described further herein) is released, the buffer spring  41  causes the buffer  42  to act on a bolt and carrier assembly (comprising a carrier  31  and a bolt  33 , as shown in Exhibit A2), to strip and (schematically shown in  FIG. 4 ), and insert a new cartridge from a magazine (shown at 1 in Exhibit A1). 
     According to the principles of the present invention, the semi bolt receiver assembly  100  has a manually operable handle  120  that is coupled with the bolt and carrier assembly, in a manner that enables the bolt and carrier assembly to be manipulated by a shooter to charge the rifle (i) while the shooter is maintaining a shooting position and (ii) without removing the shooter&#39;s hand from the pistol grip  74 . The bolt and carrier assembly is of a conventional configuration, e.g. comprising a bolt carrier  31  and bolt  33  as shown in Exhibit A2 and in the Figures. The handle  120  is coupled with the bolt carrier assembly, in a manner described herein, such that the operation of the manually operable handle  120  in charging the rifle is a substantially a straight pull action, while the shooter is maintaining a shooting position. 
     Thus, as seen in  FIG. 1 , and in Exhibits B-D, a shooter is holding a rifle with a semi automatic base (e.g. comprising Buttstock  104 , trigger  65  and pistol grip  74 ) and a semi bolt receiver assembly  100  according to the principles of the present invention. In Exhibit B, the shooter is squeezing the trigger to fire the rifle. In Exhibit C, the shooter is pulling the handle  120  to discharge a spent cartridge from the rifle, and as shown in Exhibit C, as the shooter is pulling the handle, the shooter&#39;s hand remains on the pistol grip  74 . In Exhibit D, the shooter has released the handle  120 , but (although not shown) the shooter&#39;s thumb remains about the pistol grip  74 . As the handle  120  is released, the buffer spring  41  causes the buffer  42  to act on the bolt and carrier assembly to strip (see  FIG. 4 ) and load (insert) a new cartridge from the magazine ( 1  in Exhibit A1) into the rifle chamber, in position to be fired. Thus, as will be appreciated by those in the art, the rifle according to the present invention provides the bolt action as the handle is pulled, is like a bolt action rifle in that there is no diversion of combustion gas when the rifle is fired and has the semi automatic rifle feature of utilizing the buffer spring  41  and buffer  42  to act on the bolt and carrier assembly when the handle  120  is released, to strip and insert a new cartridge, in the manner of a semi automatic rifle. 
     In the semi bolt receiver assembly  100  of the present invention, the manually operable handle  120  is coupled with a handle mount  122  that has a portion which extends through a side opening  123  in a web portion  125  of a receiver  101  that forms part of the semi bolt receiver assembly  100 . The height H of that portion of the receiver  101  that includes the web  125  is preferably at least 2.25 inches (see  FIG. 7 ), to enable the handle  120  to be supported in the manner described further herein, and to be located in a convenient manner to enable a shooter to operate the rifle in the manner illustrated in Exhibits B-D. 
     When the semi bolt receiver assembly  100  is configured by modifying an existing AR 15 type upper half, the semi bolt receiver assembly is configured to restrict diversion of a portion of combustion gas that is generated when the rifle is being fired. This can be done, e.g. by providing a barrel band  124  ( FIG. 1 ) that covers the gas diversion port in the AR 15 rifle barrel (and also by removing the gas tube  4  (Exhibit A2), because the adaptor base is configured such that in the presence of a gas tube the bolt cannot close and the rifle cannot fired, so that the gas tube shown at  4  in Exhibit A2 must be removed, as will be further appreciated from Exhibit A3). On the other hand, if a receiver assembly is configured to operate according to the principles of for the present invention, rather than modifying an existing AR 15 type receiver, the semi bolt receiver assembly shown in  FIG. 1  would have a barrel that is configured without a gas port for diverting a portion of combustion gas that is generated when the rifle is being fired. 
     In assembling a semi bolt receiver assembly  100 , according to the principles of the present invention, an adaptor base  130  is coupled with the bolt and carrier assembly, which are contained by the semibolt receiver  101 , and the handle mount  122  (to which the handle  120  is coupled) is connected to the adaptor base. Specifically, the handle mount  122  includes a sleeve  122   a  that is fixed to a coupling portion  122   b  which, in turn is fastened to the adaptor base  130  (e.g. by one or more cap head screws that extend through openings  127  in the adaptor base). The adaptor base  130  is coupled to the bolt carrier  31 , and the adjustable handle  120  is coupled with the handle mount  122  in a manner that enables the length of pull of the adjustable handle  120  to be selectively adjusted over a predetermined range. Also, adjustable handle  120  is coupled with the handle mount  122  in a manner that enables the handle to be selectively manipulated relative to the connection portion to adjust the angle at which the handle is oriented relative to the side of the semi bolt receiver  100 . It should also be noted that the receiver assembly may have a pair of sights  140 ,  142  that would be of conventional design, where the sight  140  may be connected to a weaver rail  144  that would also be of conventional design. 
     Specifically, the handle  120  comprises a relatively straight portion  120   a,  and a portion  120   b  that extends at an angle to the straight portion  120   a.  The straight portion  120   a  is received in the sleeve  122   a  of the handle mount in a manner that enables the handle to slide relative to the handle mount and to rotate (pivot) in the sleeve  122   a.  The handle can be locked in a selected position for adjusting the pull length of the handle, by a set screw  136  and can be locked in a selected rotational (angular) orientation by a clamp nut  138  that can be tightened about the handle portion  120   a.  This allows both the length of pull of the handle, and the angular orientation of the handle relative to the receiver  101  to be selectively adjusted. In addition the handle has a knob  120   c  that is adjustable for height in order to accommodate hand size and individual style of gripping the rifle (see e.g.  FIG. 8 ). 
     In another aspect of the present invention, the bolt carrier  31  has a substantially cylindrical configuration (as is known), and the adaptor base  130  is connected with the bolt carrier by one or more fasteners  141  (see  FIGS. 3 and 8 ), each of which extends through the adaptor base and into the top of the cylindrical bolt carrier  31 . Thus, forces applied to the adaptor base  130  are directed through the cylindrical bolt carrier are along a line of action extending through the center of the cylindrical bolt carrier  31 . In essence, as those in the art will appreciate, the adaptor base  130  is coupled to the bolt carrier in a manner that it replaces the bolt carrier key  28  of the conventional bolt carrier assembly of Exhibit A2. That enables the adaptor base  130  to be coupled to the bolt carrier at a relatively strong location, and to channel forces applied from the handle along a line of action that is substantially downward along a line of action through the center of the cylindrical bolt carrier  31 . Such a coupling is designed to minimize the risk of the connection between the handle  120  and the bolt carrier assembly from breaking or becoming deformed as the handle is being repeatedly operated. 
     Thus, as will also be appreciated by those in the art, with a semi bolt receiver assembly according to the present invention, assembled with rifle base that has a buttstock and pistol grip configured for semi automatic operation, the connection between the handle and the bolt and carrier assembly enables the orientation of the handle relative to the bolt and carrier assembly to be selectively adjusted to a plurality of operating orientations relative to the bolt and carrier assembly and in a manner that enables the handle to charge the bolt and carrier assembly when the handle is in any of the plurality of operating orientations. The connection between the handle and the bolt and carrier assembly is designed to enable the shooter to charge the rifle with a straight pull action, and without removing the shooter&#39;s hand from the pistol grip of the rifle. This enables relatively rapid firing of the rifle, in a manner that is like that of a semi automatic rifle, but avoids the various issues that are described herein that result from the diversion of combustion gas that is associated with operation of a semi automatic rifle. 
     In the modification shown in  FIGS. 5-8 , the adaptor base  130  has a slightly different configuration than that shown and described in  FIG. 3 , but retains the features described above, in terms of providing a relatively strong coupling between the handle  120  and the bolt and carrier assembly, and in providing for adjustment of the pull length of the handle and the angular position of the handle. In addition,  FIG. 7  illustrates the added height of the receiver  101 , in the extended web area  125  that accommodates the slot  123  for the handle, and the manner in which that added height is used to provide the handle in a convenient operating position, in accordance with the principles of the present invention. Specifically, as shown in  FIG. 7 , the added height of the receiver  101  is provided in the web portion  125  that adds about ½ inch to the overall height of the receiver  101  (compared to a standard A3 receiver), so that the receiver  101  is at least about 2.25 inches in overall height. That added web portion carries the slot  123 , and the handle mount  122  has a portion  122   c  extends through that slot, so that the handle mount sleeve  122   a  into which the handle portion  120   a  fits is located on a side of the receiver  100 , and the handle portion  120   b  extends angularly downward relative to the receiver at a convenient angle to be grasped by a shooter and operated in the manner described herein. 
     It is believed the following description will further enable those in the art to appreciate the structure and operation of the semi bolt receiver assembly of the present invention. 
     The AR15 Rifle is one of the most versatile and affordable rifle designs ever conceived and certainly the most modified and adapted beyond its intended military use. In recent years it has become the most widely used target rifle in certain competitive disciplines and new dedicated variants appear frequently. 
     The rifle is divided into an upper and lower half (Exhibits A1, A2). The lower half contains the trigger mechanism and holds the ammunition. It is the registered part of the rifle. The upper half, which this invention concerns, contains the bolt and carrier assembly, the barrel, sights and special purpose attachments. It can be configured in many ways. Because of its modular design it is possible to have one lower half and many upper halves each dedicated to a different type of shooting or purpose because each will mate to the lower half. The invention proposed herein was inspired primarily by a desire to improve the performance of the rifle in the target shooting disciplines but should have diverse appeal. 
     If the AR15 Rifle has a drawback, in the sport of target shooting, it is the gas operated self-loading system that employs parts that move during the shot process. It is an undesirable characteristic that can affect accuracy and many top competitors prefer to use a traditional or specialized bolt action rifles in long-range events, bench rest competition, or varmint hunting; all of which demand extreme accuracy. The bolt-action rifle operates with a closed bolt throughout the firing process and causes no disturbance to the rifle when it is fired. However, despite having an edge in accuracy the bolt action rifle has its own drawbacks. For example, in NRA “Match Rifle” competition there are two separate rapid-fire stages in the match that are conducted at different ranges and from different positions. Many shooters have difficulty firing all the required shots accurately due to the time it takes to manually operate the bolt; which must be raised to unlock the bolt, pulled to extract the spent cartridge, pushed in order to extract a cartridge from the magazine and chamber it, and lowered in order to lock the bolt. Sometimes the shooter must raise his head off the stock to avoid the retracting bolt. In the prone position it is sometimes necessary to lift ones arm from the shooting mat, in order to operate the bolt. The more expensive bolt action competition rifles incorporate features that overcome these drawbacks but most shooters cannot afford them. All of these circumstances cause the “position” of the shooter to break down. At these short and middle range events, which are fired at 200 to 300 yards the self-loading AR15 rifle enjoys an advantage because the shooter does not have to manipulate a bolt. The same rifle must be used across the entire course of fire. 
     When the match moves back to the 600-yard slow fire stage the bolt-action rifle assumes an advantage because there are no moving parts during the shot process. The scores at this stage generally determine the winner of the match. With the recent offering of improved cartridges and calibers for the AR15 the bolt-action does not enjoy the complete dominance that it once had at long range, but it is often preferred. 
     The invention described herein seeks to address the issue of accuracy and retain most of the speed advantage enjoyed by the AR15 with a semi bolt-action configuration. It also has the added benefit of a much cleaner action with less wear and requires less lubrication and maintenance by way of eliminating the gas operating system which fouls the action. It also makes it ergonomically feasible to shoot accurately in timed shooting events that until now have been impractical with other conversions. The application is intended primarily for rifles that would normally employ an AR 15 A3 flattop upper receiver (Exhibits B-D) which often requires the use of a scope, as in bench rest shooting, or sophisticated iron sights as in NRA Match Rifle competition. It may be adaptable to other variants as well. The principles of the present invention are particularly useful in configuring a semi bolt receiver assembly that can be assembled with a rifle base or lower receiver that is substantially conformable to the standards of existing AR15/M16 rifles, as will be clear to those in the art. 
     When a shot is fired in an unmodified AR15 Rifle, gas pressure from the propellant pushes the bullet down the barrel as in any other rifle. At a point approximately two thirds of the way down the barrel is a small gas port manifold that bleeds off a small portion of combustion gas as the bullet passes the hole. This gas is partially expelled into the action through a gas tube rearward to the rifle action where it enters the carrier key that sits atop the bolt carrier. The carrier key (Exhibit A2) diverts the gas to the inside and back of the bolt recess The carrier acting as a barrier to the gas, is pushed rearward which, via a cam pin, causes the bolt to unlock from the chamber and begin the extraction of the spent cartridge. When the bolt carrier has reached its rearmost position the spent cartridge is ejected and gas is expelled into the action. Simultaneously the bullet exits the barrel. The bolt carrier has compressed a buffer spring, located in the buttstock of the rifle, which then pushes the bolt and carrier assembly forward. A cartridge is stripped from the magazine, is chambered, and the bolt is closed via the bolt cam pin. The rifle is ready to fire again. It is this movement of the bolt and carrier during the firing process that leads to inaccuracy. It also leads to fouling of the action that is undesirable in any rifle much less one used for competition. 
     In a retrofit application the semi-bolt conversion is accomplished by first removing the gas tube and manifold and then covering the hole with a barrel band (see e.g.  FIG. 1 ) that is secured to the barrel either by a setscrew or adhesive. This will prevent any gas from escaping except from the muzzle of the barrel. This operation is only necessary when converting existing barrels. New barrels can be manufactured without the gas port; thereby eliminating the need for the barrel band. 
     All the remaining steps are common to retrofit and new manufacture upper halves. A newly designed, taller, upper receiver assembly ( FIG. 7 ) is employed in order to facilitate the use of a semi-bolt action adapter base and side-charging handle ( FIGS. 1-4 , Exhibits B-D). Near the top of the receiver assembly a slot milled into the web under the sight rail, in order to accept the handle assembly which attaches to the base ( FIG. 7 ). The adapter base is composed of a mild steel block that is attached by screws to the standard bolt carrier and replaces the carrier key and the charging handle (shown at  4  in Exhibit A1). The side-charging handle  120  of the present invention, which is adjustable, is attached to the adapter base, and is parallel to the side of the receiver. As a safety feature, the forward portion of the adapter base prevents the bolt from closing if a gas tube is present (see Exhibit A3), thereby requiring removal of the gas tube when a receiver assembly according to the present invention is being retrofitted to an existing AR 15. 
     The operation of the rifle is much the same as before the modification. All safety features remain in place. When a cartridge is fired the bolt remains closed without disturbing the rifle. The shooter extracts the round at his or her discretion by simply pulling back on the bolt handle to its rearmost position. The bolt cam pin rotates as before. The bolt carrier goes to the rear as before, the buffer spring is compressed, and the spent cartridge is ejected. But no gas is expelled (diverted) during that action and it took about one second. To charge the rifle again only involves releasing the bolt handle. The buffer spring advances the bolt and carrier, strips the cartridge from the magazine, chambers the round and closes the bolt via the bolt cam (shown in Exhibit A2). The rifle is ready to fire. The extraction, ejection, and charging of the rifle is accomplished in a single motion. The shooter does not have to make four separate acts to operate the bolt. Neither did he have to remove his hand from the pistol grip of lift his elbow. Adjustability is essential to facilitate the least movement of the firing hand which minimizes deterioration of position. That is accomplished by the bolt handle which is adjustable for length of pull, height, and angle. More time is gained to reacquire the sight picture, sight alignment, and trigger control than is possible for bolt-action shooters in rapid-fire stages. At longer ranges, shooters benefit from the fact that the rifle undergoes no cycling induced movement during the shot due to the elimination of the gas operation of the bolt. All shooters will benefit from not having to clean dirty deposits from their actions. 
     I have called it a semi-bolt action because after the conversion it is no longer a semi-automatic, but neither is it a true bolt-action. Properly speaking it would be, by default, a spring assisted straight pull action design. The straight pull action design has been around for nearly 100 years and was first widely employed in the Swiss K31 military rifle. Until the advent of semi-auto rifles the K31 straight pull rifle was the fastest manually loaded rifle available. It ejected the spent round and cocked the rifle on the rearward stroke and stripped a new round and chambered it on the forward stroke. Nearly all semi-auto and automatic rifles employ some form of gas assisted extraction and spring assisted loading variation of a straight pull design. 
     Other attempts to modify the AR15 to bolt action were primarily inspired in Great Britain where semi-auto rifles are restricted. Competitive shooters had to find ways to disable the self loading aspects of their rifles in order to compete legally. Bradley Arms offers a “bolt action” AR15 for sale in the UK that employs a side charging handle which attaches to the sidewall of the bolt carrier. In the U.S. various companies have used this method in bolt action and semi-auto as well. All of them involve threading a stud of some sort into the sidewall of the bolt carrier and notching the receiver to some degree. Neither the receivers or the bolt carriers were designed for this type of modification and there is a history of bolts and or studs breaking in some versions. Some of the receiver cuts are so extreme that it is hard to imagine they do not undermine the integrity of the receiver. All of them give the appearance of being an afterthought and most designs leave a hole where the original charging handle has been eliminated. (photo 1). 
     Due to the bolt carrier being several inches above the pistol grip, and the sidewall of the bolt carrier having only 3/16″ purchase, the side of the bolt carrier is a poor location for the kind of leverage and strain that are introduced by the bolt handle. It was not intended for that. Some conversions appear to be attempting the same thing as the semi-bolt design but cannot fully incorporate the vertical component of the bolt handle due to the extreme leverage against the bolt carrier. The shooter cannot reach the handle without lifting the hand from the grip. The single point attachment at the front of the bolt carrier, combined with the long reach of the bolt handle, makes it impossible to have the sufficient vertical drop on the handle that would enable one to manipulate the bolt without causing undue strain. It was necessary for me to address this problem early on in the testing of my own design and it led me to shy away from the obvious drawbacks of attaching to the side of the bolt carrier and skeletonizing the sidewall of the receiver. It became necessary to redesign the receiver in order to retain its strength and to take advantage of the existing mortise and mounting holes on the top of the bolt carrier that become available when the gas key is removed. This method places the strain at the strongest part of the receiver; where it is contained by the web under the sight rail. This resulted in raising the sight rail by ½″ and had the added benefit of improving the sight picture for most shooters. In addition it provided more height and surface area in order to resist rotational leverage against the bolt carrier and maintain its proper alignment. 
     The semi-bolt method includes a built in safety feature that other conversions do not. The base adapter is extended so that when it is coupled with the bolt and carrier assembly, in the manner described herein, in the presence of a gas tube the bolt cannot close and the rifle cannot fire. The proposed receiver design contains no hole for the gas tube and the millwork to accommodate the original charging handle has been eliminated. The semi-bolt system will not allow the simultaneous use of gas system parts; specifically the gas carrier key and the gas tube. Conversions which use a standard receiver and mount a handle on the side of the carrier are capable of being reconverted to semi auto. This causes a dangerous condition when a left handed person shoots a right handed gun that has a handle which extends to the rear. If an extended handle is present on a semi auto gun it is possible for the shooter to be hit in the face by the handle. No such danger exists with the semi-bolt system because it is a dedicated single shot system with integral safety features which if removed will essentially disable the gun. 
     Being that the AR15 is a modular platform very few specialized tools are required to build or modify a rifle. Many shooters prefer to build, rebarrel and modify their riffles themselves. For that reason retrofit kits could be offered to shooters and gunsmiths. These would include the receiver, adapter base, a handle particular to the desired shooting discipline, and the barrel band to block the gas if necessary. Complete upper halves could be offered as well as complete rifles. 
     Commercially viability is almost certain. The proliferation of AR15 variants in recent years continues unabated. A well thought out, user friendly, bolt action would have appeal in several different aspects of the shooting sports. For example: a bolt action AR15 would overcome the stigma of it being a rifle suitable only for military use and target shooting. There is a prejudice against semi-auto rifles being used for game hunting because it is considered unsporting to shoot anything but a bolt action. Some major firearms manufacturers have semi auto hunting variants available but it is uncertain whether they have made significant inroads on the market. A bolt action AR15 upper might appeal to those who already own an AR but hunt with traditional bolt action rifles. An immediate niche would be found in Highpower Rifle competition for the reasons previously explained. In addition the improved utility of the semi-bolt design will inspire many to upgrade their current conversions to the new design. 
     The semi-bolt conversion enables one to dry fire practice sequential fire stages of a match. Dry firing is a practice technique where the shooter, using dummy rounds, fires the gun in order to develop sight alignment, trigger control, position, and timing. Semi-auto shooters cannot dryfire practice the ten shot strings of a rapid fire because the dummy rounds cannot actuate the bolt cycle. 
     Already there exists in Great Britain a market for bolt action AR15 rifles. In varmint hunting the AR is already very popular and would be even more so if greater accuracy can be obtained. The same is true for benchrest shooting where semi auto rifles are unable to compete at the championship level. The semi-bolt variant design would fill a long standing void in the evolution of the AR15 rifle. 
     Thus, as seen from the foregoing detailed description, the present invention provides a new and useful concept that provides a semi bolt action receiver assembly that is configured for assembly with a semi automatic rifle base, to retain the speed of operation of a semi automatic rifle, while also provide the ease of operation and accuracy features of a bolt action rifle. With the foregoing description in mind, it is submitted that the manner in which such genre of semi bolt action receiver assemblies can be produced, or retrofit to existing semi automatic rifle bases, will be apparent to those in the art.