Abstract:
Embodiments of the present disclosure provide modifications to the AR-15/AR-10/M16 platform operating system such that the platform now is competent to fire belted or non-belted cartridges, including but not limited to: .300 Winchester; belted Winchester Magnum cartridges selected from the group consisting of the 264 Win Mag, 7 mm Win Mag, 300 Win Mag, 338 Win Mag, and the 458 Win Mag; 240 Weatherby; 7 mm Remington Mag; 7 mm Ultra Mag; 300 Ultra Mag; 338 Ultra Mag; 338 Edge; 338 Lapua; 458 Lott; 375 H &amp; H; and the 300 H &amp; H. The embodiments of the present disclosure allow longer range and greater barrier penetration without substantially altering the characteristic features and component inter-relationships of the AR15/AR 10/M16 platform.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Provisional Application No. 61/874,216 filed Sep. 5, 2013, Provisional Application No. 61/879,311 filed Sep. 18, 2013 and Provisional Application No. 61/926,299 filed Jan. 11, 2014, which are hereby expressly incorporated in their entirety by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This application relates to semi-automatic and automatic rifles. More particularly, the present application relates to the operating system of firearms in the AR series of firearms. Specifically the application concerns an AR platform operating system competent to receive and fire a belted cartridge in such firearms, particularly belted cartridges having greater distance and kinetic energy than the 7.62×51 mm NATO cartridge. 
       BACKGROUND 
       [0003]    The AR family of weapons and their derivatives to include indirect gas operated versions, have been in use by the military and civilian population for many years. Firearms based on the AR family, including the AR-10, the AR-15 and the M16, are the primary weapon of choice for military units in the United States and abroad. It also is a rifle platform of choice among civilian sport marksmen and hunters. 
         [0004]    Currently, this firearm platform is configured only for beltless (rimless) cartridges. This feature of the AR platform limits the choice of ammunition available for rifles in this family. In particular, it limits the shooting distance and barrier penetration possible with this platform. Currently, rifles in this family have a maximum range of about 800 meters, and a kinetic energy of less than 2,400 ft lbs, exemplified by the 7.62×51 mm NATO cartridge. Rifles in this platform also tolerate a maximum operation pressure in the range of about 50,000 psi. 
         [0005]    Belted cartridges are cartridges having a shell casing with a pronounced “belt” around its base that continues 2-4 mm past the extractor groove and allows for proper head-spacing in more powerful and larger cartridges. The addition of the belt to the casing prevents over-insertion into the chamber, which can lead to catastrophic failure of the gun when fired with excessive headspace. 
         [0006]    The use of larger and more powerful cartridges than those that can be used in the current AR platform are gaining popularity both in the military and in law enforcement, as well as among target shooters and big-game hunters. As one example, the .300 Winchester Magnum, a belted cartridge competent to travel over 1,800 meters with a kinetic energy in the range of about 3,800-4,000 ft lbs, is the most popular .30 caliber magnum with American hunters. It also is being adopted by law enforcement and certain branches of the military for long-range sniping and marksmanship. The desire for larger, more powerful (and belted) cartridges is at odds with the current AR platform. 
         [0007]    There remains a need, therefore, for a modified AR platform competent to accept belted cartridges, particularly larger cartridges that safely, accurately and reliably extend the range and barrier penetration of the existing platform, while tolerating the enhanced pressures (in the range of at least about 65,000 psi) that these cartridges generate when firing. Particularly advantageous would be the ability to provide such a modified platform without substantially altering the characteristic features of the platform that have made it a weapon of choice. 
       SUMMARY 
       [0008]    This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended on its own to identify key features of the claimed subject matter, nor is it intended to be used on its own as an aid in determining the scope of the claimed subject matter. 
         [0009]    In accordance with one embodiment of the present disclosure, provided is a firearm from the AR family or platform having a gas operated firing system, either a direct or an indirect gas operated derivative, modified to be competent to receive and safely, reliably and accurately fire a belted cartridge. As used herein, “AR platform” and “AR family” includes automatic and semi-automatic weapons, including the AR-10, the AR-15 and M-16 rifles. The ability of the AR-10/AR-15/M16 platform to receive, engage, and fire large caliber belted cartridges is achieved by the use of high strength alloys, and the specified dimensions of the components further discussed herein. In one preferred embodiment, the belted cartridge enhances the range and barrier penetration of the AR platform. In another preferred embodiment, the modified AR platform described herein has a range of at least about 1,000-1,800 m. In another preferred embodiment, the modified AR platform described herein can fire ammunition with a kinetic energy of about 4,000 ft lbs, and has a barrier penetration capability in the range of at least about twice that of the 7.62×51 mm NATO cartridge. In still another preferred embodiment, the modified AR platform described herein accommodates pressures in the range of at least about 60,000 psi, more preferably at least about 65,000 psi when firing. In another preferred embodiment, the modified AR platform described herein accommodates pressures of at least in the range of about 80,000 psi. 
         [0010]    In accordance with one embodiment of the present disclosure, provided is a firearm from the AR family having a gas operated firing system, either direct or an indirect gas operated derivative, modified to receive and safely, reliably and accurately fire a cartridge having a case length greater than 2.015 inches, an overall length greater than 2.800 inches, a base diameter greater than 0.4709 inches and a case capacity greater than 56 gr H20. In one preferred embodiment, the modified AR platform disclosed herein accommodates a cartridge having a case length in the range of about 2.62 inches, an overall length in the range of about 3.34 inches, a base diameter in the range of about 0.532 inches, and a case capacity in the range of about 90.4 gr H20. In another preferred embodiment, the modified AR platform disclosed herein accommodates a .300 Winchester cartridge. In still another preferred embodiment, the modified AR firearm disclosed herein accommodates a belted Winchester Magnum cartridge. In still another preferred embodiment, the belted Winchester Magnum cartridge is selected from the group consisting of the 264 Win Mag, 7 mm Win Mag, 300 Win Mag, 338 Win Mag, and the 458 Win Mag, or any case designed or derived from 300 H and H, either full length or shortened. 
         [0011]    In accordance with still another embodiment of the present disclosure, provided is a firearm from the AR family having a gas operated firing system, either direct or an indirect gas operated derivative, modified to receive and safely, reliably and accurately fire a belted cartridge of greater length, mass and/or diameter than a .308 Winchester without substantially altering the inter-relational features and components of the AR platform. In one preferred embodiment, the modified AR platform disclosed herein maintains the integrity of the inter-relational fire assembly components of a standard or currently existing AR rifle. In another preferred embodiment, the trigger, hammer, safety, stock, grip, takedown pins, forearm, trigger group assembly, adjustable gas block, gas tube, pins, springs, buffer tube, buffer and spring, cam pin, carrier key, bolt stop latch, and mag release butt-stock assembly, as well as their operational or functional relationship with one another, remain unaffected. 
         [0012]    In accordance with still another embodiment of the present disclosure, provided is a firearm from the AR family having a gas operated firing system, either direct or an indirect gas operated derivative, comprising an AR firearm assembly having an overall length in the range of about 10.700-10.800 inches, more preferably about 10.700-10.728 inches. In one preferred embodiment, the overall length of the modified firearm assembly is increased in the range of about 0.9-1.5 inches, more preferably in the range of about 0.95-1.3 inches, when compared with an AR-10 firearm assembly. As used herein, the term “firearm assembly” is understood to comprise: (a) upper and lower receivers; (b) bolt and bolt carrier and their associated components, including charging handle, firing pin and spring; (c) gas block and (d) barrel chamber. In accordance with still another embodiment of the present disclosure, provided is a firing pin for use in a firearm from the AR family having a gas operated firing system, either direct or an indirect gas operated derivative, having an overall length in the range of about 4.8-52 inches, more preferably in the range of about 5.05-5.10 inches. In another embodiment, the firing pin of the present disclosure differs from a standard AR-10 firing pin by having an overall length that exceeds the overall length of an AR-10 firing pin about 1.5-1.85 inches, more preferably 1.7 to 1.8 inches. In another embodiment, the firing pin further comprises a spring defining a central channel and having an overall length in the range of about 0.490-0.510 inches, more preferably 0.493-0.497 inches; an overall diameter in the range of about 0.030-0.038 inches, more preferably 0.032-0.035 inches; and a spring wire diameter in the range of about 0.025-0.035 inches, more preferably 0.028-0.033 inches. In still another embodiment the central shaft of the firing pin disclosed herein comprises a standard gas flange, the shaft passes through the channel defined by the spring, and the gas flange diameter is dimensioned to act as a bracer or backstop for the spring. In still another embodiment, the spring is competent to inhibit firing pin inertia from accidentally discharging the firearm. Said spring is not required for functionality; however, safety is enhanced by the inclusion of said spring. In still another embodiment, the firing pin disclosed herein has a maximum mass of about 0.02-0.04 lbs, more preferably about 0.02-0.03 lbs. In one preferred embodiment, the firing pin comprises one or more lightening cuts at the distal, non-primer striking end of the pin, distal to the gas flange, so as to remove unneeded mass from the pin. Alternatively or, in addition, the mass of the pin is managed by the choice of base material. For example titanium or another light material may be chosen instead of steel. Those of ordinary skill in the art will appreciate that, if desired, a clearance relief also can be added to the striking tip of the firing pin. 
         [0013]    In accordance with still another embodiment of the present disclosure, provided is an upper receiver for use in a firearm from the family having a gas operated firing system, either direct or an indirect gas operated derivative, comprising a mounting rail cut to Picatinny standards and having an overall length in the range of about 8.6-9.6 inches, more preferably in the range of about 9.5-9.6 inches. In another embodiment, the mounting rail disclosed herein differs from a standard AR-10 mounting rail by having an overall length increase in the range of about 0.9-1.5 inches, more preferably 0.95-1.3 inches. In still another preferred embodiment, the additional distance is added over the ejection port of the upper receiver. In still another embodiment of the present disclosure, the ejection port of the upper receiver has an overall length increase in the range of about 0.9-1.5 inches, more preferably 0.95-1.3 inches, when compared with the ejection port of a standard AR-10 upper receiver. In still another embodiment, the ejection port of the present disclosure has an overall longitudinal dimension in the range of about 3.4-4.5 inches, more preferably 4.0-4.45 inches. 
         [0014]    In accordance with yet another embodiment of the present disclosure, provided is a charging handle for use in a firearm from the AR-15/M16 family having a gas operated firing system, either direct or an indirect gas operated derivative, the charging handle having an overall length in the range of about 8.9-9.5 inches, more preferably in the range of about 8.95-9.3 inches. In another preferred embodiment, the charging handle disclosed herein differs in length from a standard AR-10 charging handle by having an overall length increase in the range of about 0.90-1.5 inches, more preferably 0.95-1.3 inches. In still another preferred embodiment, the charging handle disclosed herein has a tensile strength in the range of about 50,000 KSI of yield. In still another preferred embodiment, the charging handle disclosed herein has sufficient tensile strength to preclude or substantially inhibit bending of the charging handle during operation of the firearm. In one preferred embodiment, the desired tensile strength is achieved by use of a base material of greater tensile strength than 7075 aluminum. In another preferred embodiment, the base material comprises a material selected from the group consisting of titanium and steel. In still another preferred embodiment, the steel is a stainless steel. 
         [0015]    In accordance with another embodiment of the present disclosure, provided is a bolt carrier for use in a firearm from the AR family having a gas operated firing system, either direct or an indirect gas operated derivative, the bolt carrier having an overall length in the range of about 8.900-9.000 inches, more preferably in the range of about 8.65-8.80 inches. In another preferred embodiment, the bolt carrier disclosed herein differs in length from a standard AR-10 bolt carrier by having an overall length increase in the range of about 0.90-1.5 inches, more preferably 0.95-1.3 inches. In another preferred embodiment the overall diameter of the bolt carrier is substantially the same as that for a standard AR-10 bolt carrier, having a diameter in the range of about 1.1875 inches. In still another embodiment, the bolt carrier hammer ramp length is modified by increasing the length prior to the ramp, while the ramp angle remains unaffected. In this embodiment, the lengthened ramp aids in protecting the firing pin as the hammer is retracted and engaged on the secondary sear, or disconnector, of the trigger assembly. In still another preferred embodiment, the bolt carrier hammer ramp length and angle are substantially the same as that for a standard AR-10 bolt carrier, and the hammer ramp position is modified such that it is ends 4.800-4.850 or more preferably inches from the posterior end of the bolt carrier and begins 2.900-2.998 or more preferably 2.972 inches from the anterior end of the bolt carrier. In still another preferred embodiment, the opening in the bolt carrier lower surface defining the hammer clearance is located about 0.260 inches from the posterior end of the carrier and extends forward towards the anterior end a length of 4.5 to 4.700 or more preferably 4.580 inches. In still another embodiment, the relative positions of the hammer ramp and hammer clearance to one another are lengthened as that for a standard AR-10 bolt carrier to effectively lighten the mass of the new carrier. 
         [0016]    In still another embodiment, the bolt carrier comprises one or more relief cuts to reduce the overall mass of the carrier. In a preferred embodiment, the relief cuts are made to the bolt carrier shaft, particularly to the upper and lower portions of the shaft. In still another embodiment, the upper relief cut begins in the range of about 4.25-4.85 inches, more preferably 4.50 inches, from the anterior or front end of the bolt carrier and extends for a distance in the range of about 3.250-4.400 inches, more preferably 4.105 inches. In another preferred embodiment the depth of the upper relief cut is in the range of about 0.200-0.300 inches, more preferably 0.250 inches. In still another preferred embodiment, the lower relief cut begins in the range of about 4.000-4.500 inches, more preferably 4.060 inches from the front or anterior end of the bolt carrier and extends for a distance of about 2.400-4.600 inches, more preferably 4.550 inches. In another preferred embodiment, the depth of the lower relief cut is in the range of about 0.150-0.300 inches, more preferably 0.204 inches. In another preferred embodiment the base material for manufacture can include but is not limited to high strength alloys that are heat treatable such as 9310, 8620 17-4 as well as the original Carpenter 158, with 9310 being the preferred embodiment with the heat treat specification as would be known to those skilled in the art. 
         [0017]    In accordance with another embodiment of the present disclosure, provided is a bolt for use in a firearm from the AR family having a gas operated firing system, either direct or an indirect gas operated derivative, the bolt having a bolt face diameter in the range of 0.530-0.540 inches, more preferably in the range of 0.533-0.537 inches. In another preferred embodiment, the bolt disclosed herein is competent to accommodate a cartridge of greater dimensions than standard cartridges for the AR family of rifles. In still another embodiment, the bolt disclosed herein is competent to accommodate a bolt larger in a dimension than a 7.62-51 mm NATO cartridge or a 5.56×45 mm NATO cartridge. 
         [0018]    In accordance with another embodiment of the present disclosure, provided is a bolt extractor for use in a firearm from the AR family having a gas operated firing system, either direct or an indirect gas operated derivative, the bolt extractor having an extractor groove of a dimension in the range of about 0.260-0.281 radius inches, more preferably in the range of about 0.263-0.268 radius inches. In still another preferred embodiment, the radius of the bolt extractor groove is dimensioned to engage the rim of a belted cartridge. In still another preferred embodiment, the modified bolt extractor groove radius is competent to engage a belt of a .300 Winchester Magnum or larger caliber cartridge. In accordance with another embodiment of the present disclosure, provided is a chamber for use in a firearm from the AR platform having a gas operated firing system, either direct or an indirect gas operated derivative, wherein the chamber wall thickness has a range of about 0.250-0.350 inches, more preferably 0.250-0.285 inches. In another preferred embodiment, the chamber comprises a chamfered radius of about 0.015-0.040 more preferably 0.025 at the posterior end of the chamber to facilitate feeding of a cartridge into the chamber. In still another embodiment, the chamber comprises a belt seat proximal to and anterior to the chamfer to act as a counter bore for the cartridge belt and thereby “seat” the cartridge, establishing proper head space. In one preferred embodiment, the chamfer has a length in the range of about 0.01-0.04 inches, more preferably in the range of 0.02-0.03 inches; and an angle in the range of about 20-60 degrees, more preferably 30-45 degrees. In another preferred embodiment, the chamber has a counter bore seat dimension (depth) of 0.0905-0.0965 inches. 
         [0019]    In accordance with another embodiment of the present disclosure, provided is a lower receiver for use in a firearm from the AR platform having a gas operated firing system, either direct or an indirect gas operated derivative, the lower receiver having an overall length in the range of about 9.50-10.50 inches, more preferably in the range of about 10.070 inches. In another embodiment, the lower receiver disclosed herein differs from a standard AR10 lower receiver by having an overall length increase in the range of about 0.9-1.5 inches, more preferably 0.95-1.3 inches. In another preferred embodiment, the length increase in the lower receiver occurs in the longitudinal dimension of the magazine well. In still another preferred embodiment, the magazine well disclosed herein differs from the magazine well of a standard AR-10 lower receiver by having an overall length increase in the range of about 0.9-1.5 inches, more preferably 0.95-1.3 inches. In another preferred embodiment the magazine well of the present disclosure has a longitudinal dimension in the range of about 3.90-4.55 inches, preferably 3.95-4.45 inches. In another preferred embodiment, the magazine well of the present disclosure has a width in the range of about 0.30-1.10 inches; preferably 0.36-1.05 inches. 
         [0020]    In accordance with another embodiment of the present disclosure, provided is a magazine for use in a firearm from the AR platform having a gas operated firing system, either direct or an indirect gas operated derivative, the magazine having a double stack capacity competent to receive belted cartridges and competent to fit and operate in the magazine well disclosed herein. In another embodiment, the;double stack capacity magazine disclosed herein is competent to receive belted or non-belted cartridges ranging in length from about 2.800-3.625 inches. In still another embodiment, the magazine has external dimensions ranging in length from about 3.100-4.200 inches, more preferably 4.100 inches, a width ranging from about 1.000-1.500 inches, more preferably 1.125 inches, and a height ranging from about 2.0-8.0 inches, more preferably 5.150 inches. In still another embodiment, the magazine of the present disclosure has internal dimensions comprising a length in the range of about 2.800-4.100 inches, more preferably 3.800 inches, a width in the range of about 0.750-1.100 inches, more preferably 0.900 inches, and a height in the range of about 1.900-7.900 inches, more preferably 5.00 inches. In another embodiment, the magazine has an internal radius that aligns with the radius stacked cartridges. In one embodiment, the internal magazine radius is in the range of about 16-20 inches; in another embodiment, the radius is in the range of about 18.6 inches. Those skilled in the art will understand that preferred internal radii will be dictated by caliber choice and the radius produced by a stack of the selected caliber cartridges. In still another embodiment the magazine of the present disclosure is composed of a non-metal material of sufficient tensile strength to prevent magazine structural deformation during operation while having reduced friction during cartridge delivery as compared with a metal cartridge. In one preferred embodiment the magazine cartridge material comprises a glass-filled nylon comprising 30-50% glass composition. 
         [0021]    In still another preferred embodiment, the overall length increase in the lower receiver occurs at least in part by means of an extension at the posterior end of the lower receiver. Preferably the length of this extension is in the range of about 0.45-0.75 inches, more preferably in the range of about 0.50-0.60 inches. In yet another preferred embodiment, the remainder of the overall length increase occurs at least in part in the linear length dimension of the magazine well in the lower receiver. Accordingly, another preferred embodiment is a lower receiver for use in a firearm from the AR platform comprising a magazine well having a posterior to anterior length in the range of about 4.500-4.600 inches, more preferably in the range of about 4.510 inches. In another preferred embodiment, the magazine well disclosed herein differs in length from a standard AR-10 magazine well by having an overall length increase in the range of about 0.20-1.05 inches. In one embodiment the increase constitutes a portion of the overall length increase of the lower receiver and is in the range of about 1.100 inches, more preferably 1.105 inches. In another embodiment, the increase constitutes the total increase in the overall length and the increase has a range of about 0.9-1.5 inches, more preferably 0.95-1.3 inches. 
         [0022]    The AR platform utilizes either of two butt-stock assemblies: the rifle stock comprising a rifle length buffer and spring, and the carbine stock, comprising a carbine buffer and spring. Proper cycling of the bolt carrier into the receiver extension tube in the butt-stock is critical to reliable, safe functioning of the rifle action. In the modified AR firearm assembly disclosed herein there are two options for achieving this proper cycling with the larger caliber cartridges contemplated. Where the increase in the length of the lower receiver is achieved by increasing the magazine well by about 0.9-1.5 inches, proper cycling of the bolt carrier into the receiver extension tube can be achieved using a standard AR-10 rifle stock with a carbine buffer and spring. Alternatively, where the increase in the lower receiver length occurs by means of an extension at the posterior end of the lower receiver together with an increase in the magazine well length, proper cycling of the bolt carrier can be achieved using a carbine butt-stock with a carbine buffer and spring. Accordingly, in another embodiment of the present disclosure, provided is a firearm from the AR platform comprising a carbine buffer and buffer spring in a standard AR10 butt-stock. 
         [0023]    The modifications disclosed herein individually and together define an AR platform that (1) mechanically accommodates a larger caliber cartridge than has been possible up until now, and (2) accommodates the greater pressures generated by a larger caliber cartridge when fired. In addition, the modified platform disclosed herein achieves these results without (1) substantially negatively impacting the safety, reliability or accuracy of the platform, or (2) substantially altering the inter-relational features of the platform&#39;s components. Examples of these components include, without limitation, the spring and plunger; hammer, trigger, and their related pins and springs; and the safety, with its associated detents and springs. For these and other reasons, the disclosure presented herein provides a novel, unique and unanticipated or unobvious improvement over the rifles in the prior art. 
         [0024]    In accordance with another embodiment of the present disclosure, provided is a firearm from the AR platform, namely a firearm with a gas operating system and a dual receiver assembly, comprising: an upper receiver assembly configured for receiving magazine-fed ammunition, and having a mechanism for manually reciprocating the action of the firearm; a lower receiver assembly attached to the upper receiver assembly, the lower receiver assembly being configured to have an ammunition magazine attached thereto for supplying ammunition from the ammunition magazine to the upper receiver assembly; the upper receiver assembly being detachable from the lower receiver assembly; a buffer tube having a bore with a forwardly facing opening; a bolt carrier assembly operative with the buffer tube during firearm operation. The firearm is competent to receive and fire a belted cartridge, and tolerates firing pressures in the range of at least about 65,000 psi. In another embodiment, the firearm tolerates firing pressures in excess of 80,000 psi. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0025]    The foregoing aspects and many of the attendant advantages of this disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
           [0026]      FIG. 1  is a side perspective of an embodiment of an assembled firearm of the present disclosure; 
           [0027]      FIG. 2  is an exploded view of the firearm depicted in  FIG. 1 ; 
           [0028]      FIG. 3  illustrates one embodiment of a firing pin useful in a firearm of the present disclosure; 
           [0029]      FIG. 4  illustrates one embodiment of an upper receiver of the firearm of the present disclosure; 
           [0030]      FIG. 5  illustrates one embodiment of a charging handle useful in a firearm of the present disclosure: 
           [0031]      FIG. 6A-6E  illustrates two embodiments of a bolt carrier useful in a firearm of the present disclosure; 
           [0032]      FIG. 7  illustrates one embodiment of a bolt useful in a firearm of the present disclosure; 
           [0033]      FIG. 8  illustrates one embodiment of a bolt extractor useful in a firearm of the present disclosure; 
           [0034]      FIG. 9  illustrates one embodiment of a barrel chamber useful in a firearm of the present disclosure; 
           [0035]      FIG. 10  illustrates one embodiment of a lower receiver useful in a firearm of the present disclosure; and 
           [0036]      FIGS. 11A and 11B  illustrate one embodiment of a magazine useful in a firearm of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    Embodiments of the present disclosure provide a modified firearm assembly for the AR platform, having a gas operated firing system, either direct or an indirect gas operated derivative, and components thereof such that the platform now is configured to receive and reliably, safely and accurately fire belted cartridges, particularly belted cartridges that exceed the range and kinetic energy of the .308 cartridge. 
         [0038]    Referring to  FIG. 1 , an assembled firearm  100  of the present disclosure is illustrated. A key feature of the firearms of the present disclosure is that the firearms can accommodate larger caliber belted cartridges such as a .300 Winchester Magnum, without substantially altering the characteristic features of the firearm assembly of an AR platform rifle. One characteristic feature of this platform is the ability to interchange standard “off the shelf” components of the firearm assembly. Representative components commonly interchanged include, without limitation, the stock, grip, takedown pins, forearm, trigger group assembly, adjustable gas block, gas tube, safety, pins, springs, buffer tube, buffer and spring, cam pin, carrier key, bolt stop latch, and mag release butt-stock assembly. The modified firearm of the present disclosure does not interfere with or alter the ability to interchange these components. The firearm of the present disclosure has been modified to maintain the inter-relationship of these interchangeable components by making modifications to other aspects of the firearm assembly. 
         [0039]    Referring to  FIG. 2 , an exploded view of a firearm of the present disclosure is provided, illustrating the interrelationship and proper assembly of the components of the firearm. A number of the interchangeable components are identified, including the stock  110 , buffer tube  113 , buffer spring  111 , buffer  112 , carrier key  114 , the barrel extension  115 , and the barrel  103 . Also identified are the components that have been modified to accommodate a belted cartridge, particularly a belted cartridge of a larger caliber than the .308. These modified components include, without limitation, the upper receiver  101 , the lower receiver  102 , the magazine  129 , the barrel chamber  109 , the bolt carrier  104 , the bolt  105 , the bolt extractor  106 , the firing pin  107  and the charging handle  108 . The modifications disclosed herein to these components together both mechanically accommodate the larger caliber cartridges envisioned for use in the firearms of the present disclosure, and accommodate the higher pressures these larger caliber cartridges generate when fired. As disclosed herein below, the modifications to particular components is described. Those of ordinary skill in the art of firearm manufacture will appreciate the preferred base materials and dimensional tolerances to be chosen for these modifications, in light of the present disclosure. 
         [0040]    Referring now to  FIG. 3 , the firing pin  107  of the present disclosure and useful in the firearm assemblies of the present disclosure, comprises a shaft  12 , a firing tip end  11  at the anterior end of the pin, and a gas flange  14 . The firing pin  107  differs from the standard firing pins of the AR platform, particularly firing pins of utility in the AR-10 firearm assembly, in that the shaft length is increased by about 1.5-1.85 inches, more preferably 1.70-1.78 inches, as compared with an AR-10 firing pin. In another embodiment, the overall length of firing pin  107  is in the range of about 4.8-5.2 inches, more preferably 5.05 to 5.10 inches. The shaft diameter, overall diameter and gas flange diameter need not be substantially altered from that of an AR-10 firing pin. In addition, the firing pin  107  comprises a spring  10  defining a channel through which the firing pin shaft can pass. Inclusion of the spring keeps the firing pin inertia form accidentally discharging the firearm. The spring has a maximum diameter such that the gas flange acts as a backstop. The spring  10  has an overall length in the range of about 0.490-0.51 inches, an overall diameter in the range of about 0.030-0.038 inches, and a spring wire diameter in the range of about 0.030-0.038 inches. Those of ordinary skill in the art can determine the desired base material and compression for a spring  10 . Due to the enhanced shaft length, the firing pin  107  has a larger mass than a standard firing pin for an AR platform rifle. Typically such pins have a mass in the range of about 0.02 pounds when made of steel. A steel firing pin  107  made of steel would have a mass of about 0.04 pounds. Those of ordinary skill in the art will appreciate that the overall mass of firing pin  107  can be reduced by introducing one or more lightening cuts  16  to the posterior end of the pin, and/or by using a lighter base material that provides appropriate strength, such as titanium. It is important to reduce the firing pin mass sufficient to avoid overriding the spring and causing accidental discharge. A preferred maximum mass for firing pin  107  is in the range of about 0.02-0.04 pounds, more preferably in the range of 0.020-0.030 pounds. In addition, those of ordinary skill in the art appreciate that a clearance relief can be added to the firing tip  11  of the pin. 
         [0041]    Referring to  FIG. 4 , an upper receiver  101  is provided, comprising an integral mounting rail  20 , preferably cut to Picatinny standards, and an ejection port  22 , through which spent cartridges are released. The mounting rail and therefore the upper receiver, differs from a standard upper receiver in the AR platform, particularly an upper receiver for use in an AR-10 firearm assembly, by having an increased overall length of about 0.9-1.5 inches, more preferably 0.95-1.3 inches. In a preferred embodiment, the additional length is provided by extending the longitudinal dimension or length of the ejection port and overlying mounting rail by about 0.9-1.5 inches, more preferably 0.95-1.3 inches. The increased length of the ejection port allows the rifle to clear the larger shells of the cartridges envisioned for use in the rifles of the present disclosure. Accordingly, in one preferred embodiment the upper receiver comprises a mounting rail cut to Picatinny standards and having an overall longitudinal dimension in the range of about 8.6-9.6 inches, more preferably about 9.5-9.6 inches. In another preferred embodiment, the upper receiver of this disclosure comprises an ejection port having a longitudinal dimension in the range of about 3.4-4.5 inches, preferably 4.0-4.45 inches. 
         [0042]    Referring to  FIG. 5 , a charging handle  108  is provided. Like standard charging handles used in AR-10 firearm assemblies, charging handle  108  comprises a shaft  30 , an engagement end  34  at the anterior end of the charging handle, and a grip  32  at the posterior end. The charging handle  108  differs from a standard charging handle in that the shaft  30  has a greater length in the range of about 0.9-1.6 inches, more preferably 0.95-1.3 inches when compared with an AR-10 charging handle. In another embodiment, the overall length of the charging handle disclosed herein is in the range of about 8.9-9.5 inches, more preferably in the range of 8.95-9.3 inches. Both the grip end and the engagement end can remain as they exist for the current AR platform, that is to say, they are substantially unchanged in the charging handle disclosed herein In a preferred embodiment the charging handle, and more particularly at least the shaft  30  is composed of a base material having greater rigidity and strength than the base material 7075 aluminum used in standard charging handles. In one preferred embodiment the preferred base material of the shaft  30  comprises titanium. In another preferred embodiment, the shaft base material comprises steel, particularly stainless steel. 
         [0043]    Referring now to  FIG. 6A-6E , a bolt carrier  104  is provided.  FIG. 6A  illustrates a bolt carrier of the art  116  and of use in an AR-10 firearm assembly.  FIGS. 6B-6E  illustrate embodiments of bolt carriers  104  of the present disclosure. In particular,  FIG. 6B  and  FIG. 6C  provide two views of one embodiment of bolt carrier  104 , and  FIG. 6D  and  FIG. 6E  provide two views of another embodiment of bolt carrier  104 . Bolt carrier  104  comprises a shaft  44 , a buffer end  42  at the posterior of the bolt carrier, a bolt end  45  at the anterior end of the bolt carrier  40 , and one or more gas ports  46   FIGS. 6C and 6E . In a preferred embodiment, the bolt carrier  104  comprises at least three gas ports. In addition, both bolt carrier  104  and bolt carriers of the prior art  116  comprise a hammer ramp  50 . The bolt carrier  104  differs from a standard bolt carrier in the art  116  in that the overall length of the shaft posterior to the bolt end is increased in the range of about 0.9-1.5 inches, more preferably 0.95-1.3 inches. In a preferred embodiment the increased length is achieved by moving the hammer ramp  50  and hammer clearance  52  so as to maintain the proper relation to firing controls. In a preferred embodiment the relational distance between the hammer ramp  50  and the hammer clearance  54  remains the same as in a standard bolt carrier of the art, and they are moved back a length in the range of about 0.9-1.5 inches, more preferably 0.95-1.3 inches from the anterior bolt end  40 . In one preferred embodiment the bolt carrier hammer ramp length and angle are substantially the same as that for a standard AR-10 bolt carrier, and the hammer ramp position is modified such that it is ends 4.855 inches from the posterior end of the bolt carrier and begins 4.125 inches from the anterior end of the bolt carrier. In still another preferred embodiment, the opening in the bolt carrier lower surface defining the hammer clearance is located about 2.660 inches from the posterior end of the carrier. In another preferred embodiment the overall diameter  54  of bolt carrier  104  is substantially the same as the overall diameter of bolt carrier  116 . 
         [0044]    Referring now to  FIGS. 6D and 6E , in another embodiment, the bolt carrier of the present disclosure comprises one or more relief cuts  130  and  131  to reduce the overall mass of the carrier, thereby accommodating longer barrel lengths, lower gas pressures and varying cartridge loads, including lower cartridge loads. In a preferred embodiment, the relief cuts are made to the bolt carrier shaft  44 , particularly to the upper portions  130  and lower portions  131  of the shaft. In still another embodiment, the upper relief cut  130  begins in the range of about 3.25-4.50 inches, more preferably 4.30 inches, from the bolt carrier anterior end  40  and extends for a distance in the range of about 3.250-4.400 inches, more preferably 4.300 inches. In another preferred embodiment the upper relief cut depth  132  is in the range of about 0.200-0.300 inches, more preferably 0.250 inches. In still another preferred embodiment, the lower relief cut begins in the range of about 4.000-4.500 inches, more preferably 4.060 inches from the bolt carrier anterior end  40  and extends for a distance of about 2.400-4.600 inches, more preferably 4.550 inches. In another preferred embodiment, the lower relief cut depth  133  is in the range of about 0.150-0.300 inches, more preferably 0.204 inches. 
         [0045]    The bolt carrier relief cuts disclosed herein provide maximum flexibility for ensuring proper engagement of a bolt in the barrel extension of the rifle disclosed herein under varying gas pressures, particularly gas pressure variations corresponding to variations in barrel lengths and/or cartridge loads. As will be appreciated by those of ordinary skill in the art, shorter barrel lengths, particularly barrel lengths in the range of about 16-20 inches result in higher gas pressures, and longer barrel lengths, particularly barrel lengths in the range of about 20-24 inches, produce lower gas pressures. Higher gas pressures accommodate higher bolt carrier mass and spring tension in the buffer spring without compromising full engagement of the bolt in the barrel extension  115  (see  FIG. 2 ). Where gas pressures are lower, for example with longer barrel lengths, reducing the bolt carrier mass with one or more relief cuts allows for full and functional engagement of the bolt in the barrel extension. As also will be appreciated by those of ordinary skill in the art, the relief cut bolt carrier disclosed herein accommodates short and long barrel lengths, including barrels lengths in the range of about 16-24 inches; buffer spring tensions in the range of about 15-18 lbs of load per inch of deflection, more preferably in the range of about 17.5 lbs of load; gas pressures in the range of about 16,000-48,000 psi, more preferably in the range of about 26,000 psi, and bolt carrier mass weights in the range of about 0.700-1.1 lbs, more preferably in the range of about 0.79 lbs. It also will be understood by those of ordinary skill in the art that a range of materials are useful in the fabrication of the bolt carrier of the present disclosure, including, without limitation, stainless steel, carbon steel, particularly 86/20 carbon steel, and titanium. 
         [0046]    Referring to  FIG. 7 , a bolt  105  is provided. Like AR-10 bolts in the art, bolt  105  comprises an anterior fluted end  62 , an opening  64  for fitting a bolt extractor, a firing pin engaging end  60  at the posterior end of the bolt, and a bolt face  66  at the fluted anterior end, which defines a central channel  68  through which the firing pin tip penetrates when the rifle is fired. The overall length and diameter of the bolt  105  disclosed herein is substantially the same for an AR-10 bolt. The bolt  105  is modified to accommodate the larger cartridges contemplated for the firing assembly provided herein by increasing or opening the bolt face  66  such that it has a diameter in the range of about 0.530-0.545, preferably 0.533-0.537 inches. 
         [0047]    Referring to  FIG. 8 , a bolt extractor  106  is provided. Like AR-10 bolt extractors, bolt extractor  106  comprises an anterior cartridge engagement end, and a posterior spring end that seats in the bolt. The cartridge engagement end  72  comprises on its inferior surface a chamfer  74 , and a groove  70  defining a channel competent to engage a cartridge rim. The overall dimensions and mass of bolt extractor  106  are substantially the same as a bolt extractor of the art. The bolt extractor  106  has been modified from the prior art bolt extractor by enlarging the groove radius  74  to accommodate and engage the rim of larger caliber cartridges such as the .300 Winchester Magnum cartridge. In a preferred embodiment the radius  74  is in the range of 0.260-0.281 inches, more preferably it is in the range of about 0.263-0.268 inches. 
         [0048]    Referring now to  FIG. 9 , a cartridge barrel chamber  109  is provided. Like AR-10 barrel chambers in the art, chamber  109  comprises a barrel  88  and a cartridge chamber  86 . Together the chamber and barrel have a central opening defining channel or bore through which a bullet can travel when the rifle is fired, and exiting out the anterior or bore end  82  of the barrel chamber. The diameter of the barrel wall typically differs from the diameter of the chamber wall. In addition, the bore dimensions vary by caliber choice. The barrel chamber  109  differs from barrel chambers in the art by having a thinner chamber wall thickness. In particular, the chamber wall is reduced by about 0.060-0.063 inches, more preferably by 0.062 inches. Accordingly, preferred chamber walls for use in the cartridge barrel chambers of this disclosure will have a thickness in the range of about 0.250-0.350 inches, more preferably 0.250-0.275 inches. This range captures the minimum wall thickness achievable for accommodating a larger cartridge without compromising chamber wall integrity which can lead to catastrophic failure. It also captures the maximum wall thickness that can accommodate a larger caliber cartridge without causing jamming or cartridge feed failure. In addition, a chamfer  92  and recess  94  for cartridge belt seating are added at the posterior firing end of the chamber. The chamfer and recess, also known as a counter bore  90 , are dimensioned to allow the belted cartridge to seat and establish proper head space rear of the cartridge and bolt face. In one preferred embodiment the chamfer angle  92  has a range of about 20-60 degrees, more preferably 30-45 degrees, and chamfer length has a range of about 0.01-0.4 inches. In another preferred embodiment, the depth of the counter bore, measured as the distance between points A and B in  FIG. 9 , has a range of about 0.0905-0.0965 inches. The diameter of the counter bore  90  has a range of about 0.530-0.535 inches. 
         [0049]    Referring to  FIG. 10  a lower receiver  102  is provided. Like AR-10 lower receivers in the art, lower receiver  102  comprises standard components including a magazine well  120 . Lower receiver  102  differs from an AR-10 lower receiver by having a greater overall length in the range of about 09.0-1.5 inches, more preferably 0.95-1.3 inches. In a preferred embodiment this increased length occurs in the linear dimension  122  of the magazine well  120 . This modification allows the lower receiver to accommodate a magazine comprising any of the family of belted cartridges, particularly the larger caliber belted cartridges envisioned for use in the firearm of the disclosure presented herein. Examples of larger caliber belted cartridges include, without limitation, the 264 Win Mag, 7 mm Win Mag, 300 Win Mag, 338 Win Mag, and the 458 Win Mag. The modification also allows the lower receiver to achieve the desired increased length enabling it to engage properly with the upper receiver disclosed herein, including co-relating the position of the magazine well with the position of the upper receiver ejection port  22  while not affecting or substantially altering the inter-relationship of the other standard components on a lower receiver or upper receiver, including, without limitation, the bolt stop, spring and plunger; magazine racks; hammer and trigger and their related pins and springs; and the safety, with its associated detents and springs. Those having ordinary skill in the art will appreciate that the magazine well can be dimensioned to accommodate other preferred magazine features such as cartridge double-loading and desired cartridge capacity. 
         [0050]    The AR platform utilizes either of two butt-stock assemblies: the rifle stock comprising a rifle length buffer and spring, and the carbine stock, comprising a carbine buffer and spring. Proper cycling of the bolt carrier into the receiver extension tube in the butt-stock is critical to reliable, safe functioning of the rifle action. In the modified AR firearm assembly disclosed herein there are two options for achieving this proper cycling with the larger caliber cartridges contemplated. Referring to  FIG. 2 , the firearm assembly disclosed herein makes use of a standard rifle butt-stock  110  for use in the AR platform, particularly an AR-10 rifle butt-stock. The modified firearm disclosed herein achieves this by making use of a carbine buffer  112  and buffer spring  111 , rather than a standard rifle buffer. This allows proper cycling of the bolt carrier  104  through the buffer tube  113  of the butt stock. Alternatively, proper cycling can be achieved by adding an extension to the inferior posterior end  124  of the lower receiver. In a preferred embodiment, this extension has a linear dimension in the range of 0.45-0.75 inches. In an embodiment where this extension is built into the lower receiver, the added dimension of the extension will be subtracted from the overall longitudinal dimension of the magazine well, so that the overall dimension of a lower receiver of the present disclosure remains in the range of about 0.9-1.5 inches, preferably 0.95-1.3 inches. Where the increase in the lower receiver length occurs by means of an extension at the posterior end of the lower receiver  124 , together with an increase in the magazine well length, proper cycling of the bolt carrier can be achieved using a carbine butt-stock with a carbine buffer and spring. 
         [0051]    Referring to  FIGS. 11A and 11B  a magazine  130  having utility in the rifle of the present disclosure is illustrated. The magazine has a double stack capacity competent to receive belted cartridges and competent to fit and operate in the magazine well disclosed herein. In another embodiment, the double stack capacity magazine disclosed herein is competent to receive belted or non-belted cartridges ranging in length from about 2.800-3.625 inches. Examples of such cartridges and useful in the magazine disclosed herein includes, without limitation, the 240 Weatherby, 264 Win Mag, 7 mm Remington Mag, 300 Winchester Mag, 338 Win Mag 458 Win Mag, 7 mm Ultra Mag, 300 Ultra Mag, 338 Ultra Mag, 338 Edge, 338 Lapua, 458 Lott, 375 H and H, and the 300 H and H. 
         [0052]    The magazine assembly  130  illustrated in  FIG. 11  comprises a magazine body  129 , a follower  128 , a magazine spring  127 , a spring floor plate  126  and a magazine butt plate  125 . Useful magazine body  129  external dimensions range in length from about 3.100-4.200 inches, more preferably 4.100 inches, in width from about 1.000-1.500 inches, more preferably 1.125 inches, and in height from about 2.0-8.0 inches, more preferably 5.150 inches. Useful internal dimensions of the magazine body  129  include a length in the range of about 2.800-4.100 inches, more preferably 3.800 inches, a width in the range of about 0.750-1.100 inches, more preferably 0.900 inches, and a height in the range of about 1.900-7.900 inches, more preferably 5.00 inches. The magazine preferably has an internal radius that aligns with the radius of stacked cartridges. In one embodiment, the internal magazine radius is in the range of about 16-20 inches; in another embodiment, the radius is in the range of about 18.6 inches. Those skilled in the art will understand that preferred internal radii will be dictated by caliber choice and the radius produced by a stack of the selected caliber cartridges. As with magazine assemblies of the art, the magazine body of the present disclosure comprises a channel  134  that runs down the central longitudinal axis on the inner posterior face of the magazine body, and, opposing lips that run longitudinally down the interior lateral sides of the magazine body. The channel and lips serve to seat and guide the cartridges as they are stacked in the magazine body and travel up the body during operation of the firearm. The dimensions of the channels and lips, as well as their precise locations within the body will vary depending choice of cartridge caliber selected. With the magazine body dimensions disclosed herein, those of ordinary skill in the art will know how to select the desired channel dimensions and lip positioning for a given selected cartridge. The assembly components  129 ,  127 ,  126  and  125  can be fabricated using materials and, dimension considerations well understood in the art. The magazine of the present disclosure is composed of a non-metal material of sufficient tensile strength to prevent magazine structural deformation during operation while having reduced friction during cartridge delivery as compared with a metal cartridge. In one preferred embodiment the magazine cartridge material comprises glass-filled nylon, comprising 30-50% glass composition. 
       EXAMPLES 
       [0053]    In these illustrative, non-limiting examples, the assembly and use of modified firearm assemblies useful in the AR platform and competent to receive and fire large caliber belted cartridges are described. The cartridge selected for use in these examples is a .300 Winchester Magnum cartridge. As will be understood by those of ordinary skill in the art, the firearm disclosed herein can be constructed to receive other belted cartridges, particularly other large caliber belted cartridges, including: without limitation, the 264 Win Mag, 7 mm Win Mag, 300 Win Mag, 338 Win Mag, and the 458 Win Mag. 
         [0054]    In the examples that follow, the AR platform firing assemblies and rifles are assembled according to the exploded view depicted in  FIG. 2 . The Examples list the dimensions of the modified components selected for each rifle. In all cases the butt stock selected was a rifle length butt-stock and the buffer and buffer spring were carbine buffers and springs. Components not listed here were selected as “off the shelf.” Following assembly of the AR platform firearms of these examples, the firearms were tested according to the following cycle of operation. In both examples, the range was in excess of 1,000 m, and the pressures tolerated exceeded 65,000 psi. 
         [0055]    Firearm Operation: Firing: hammer being released by the trigger seam rotates anterior to impact the posterior end of firing pin, which travels forward, impacting the primer of the case. Rapid expansion of the burning gases are tapped off the barrel, and guided through the gas tube. The gases impinge on the bolt and carrier causing the bolt carrier to move rearward, unlocking the action. This starts the extraction process removing the fired case from the chamber while simultaneously cocking the hammer. Once the case clears the side of the ejection port, the ejector kicks the spent case from the upper receiver. While the carrier is moving rearward, it impinges on the buffer, compressing the buffer spring. Upon reaching its most rearward point, the carrier is returned anteriorly by the stored energy in the buffer spring. As the carrier continues forward, the next round is fed from the magazine and started into the chamber. At the forward-most movement of the carrier, the bolt cam pin is pivoted in the cam pin slot, allowing the bolt to rotate, locking the bolt and barrel extension; readying the firearm for the next shot. 
       Example 1 
       [0056]    UPPER RECEIVER, overall dimension: 10.700 inches, MOUNTING RAIL: 9.545 inches; BOLT CARRIER: 8.970 inches; FIRING PIN: overall length: 5.050 inches; FIRING PIN SPRING: overall length: 0.495 inches; overall diameter: 0.034 inches; spring wire diameter: 0.034 inches; CHARGING HANDLE: overall length: 9.175 inches; BOLT EXTRACTOR: extractor groove: 0.276 radius inches; EJECTION PORT: length: 4.45 inches; BOLT FACE: 0.535 inches; CHAMBER WALL THICKNESS: 0.250 inches, minimum; MAGAZINE WELL (LOWER RECEIVER): length: 4.45 inches; width: 0.36; MAGAZINE: body, outer dimensions: length: 4.1 inches; width: 1.25 inches; height: 5.15 inches; inner dimensions: length: 3.8 inches; width: 0.9 inches; height: 5.0 inches; inner radius: 18.6 inches. 
       Example 2 
       [0057]    UPPER RECEIVER, overall dimension: 10.700 inches, MOUNTING RAIL: 9.56 inches; BOLT CARRIER: 8.975 inches; FIRING PIN: overall length: 5.010 inches; FIRING PIN SPRING: overall length: 0.495 inches; overall diameter: 0.034 inches; spring wire diameter: 0.034 inches; CHARGING HANDLE: overall length: 9.00 inches; BOLT EXTRACTOR: extractor groove: 0.281 radius inches; EJECTION PORT: length: 4.40 inches, height: 0.686 inches; BOLT FACE: 0.532 inches; CHAMBER WALL THICKNESS: 0.284 inches; COUNTERBORE “Seat”: 0.0905-0.0965 inches. MAGAZINE WELL (LOWER RECEIVER): length: 3.95 inches; width: 1.050 inches; MAGAZINE: body, outer dimensions: length: 4.1 inches; width: 1.25 inches; height: 5.15 inches; inner dimensions: length: 3.8 inches; width: 0.9 inches; height: 5.0 inches; inner radius: 18.6 inches. 
         [0058]    Embodiments of this disclosure may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the disclosure being indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the disclosure.