Bolt Carrier and Bolt for Gas Operated Firearms

This is a continuation of U.S. application Ser. No. 18/200,420, filed May 22, 2023, which is a continuation of U.S. application Ser. No. 17/352,203, filed Jun. 18, 2021, now granted as U.S. Pat. No. 11,662,169, which is a continuation of U.S. application Ser. No. 16/430,865, filed Jun. 4, 2019, now granted as U.S. Pat. No. 11,067,352, which is a continuation of U.S. application Ser. No. 15/596,834, filed May 16, 2017, now granted as U.S. Pat. No. 10,309,739, which is a divisional of U.S. application Ser. No. 14/470,513, filed Aug. 27, 2014, now granted as U.S. Pat. No. 9,658,011, which is a continuation of U.S. application Ser. No. 13/841,618, filed Mar. 15, 2013, now granted as U.S. Pat. No. 8,844,424, which is a continuation-in-part application claiming benefit of U.S. application Ser. No. 13/588,294, filed Aug. 17, 2012, now granted as U.S. Pat. No. 8,950,312, which claims priority under 35 U.S.C. 119(e) to U.S. Provisional Application No. 61/524,500, filed Aug. 17, 2011, each of which is incorporated herein by reference in their entirety.

The present invention relates to gas-operated firearms and, more particularly, to an improved bolt and bolt carrier for use in such firearms.

The AR15/M16 family of firearms and their derivatives, including all direct gas operated versions, have been in use by the military and civilian population for many years. An essential part of this firearm's design is the bolt carrier which typically includes a bolt mounted in the carrier for axial sliding movement and rotation, a firing pin slidably mounted within the bolt and bolt carrier for restricted reciprocating axial movement, and a cam pin for limiting relative rotation between the bolt and the bolt carrier.

The bolt carrier is generally cylindrical in shape with a longitudinally extending circular bore throughout its length. An elongated opening is provided in the top and bottom of the carrier to allow the hammer to extend into the interior of the bolt carrier and strike the firing pin. The carrier is received and housed within the firearms receiver with the front of the carrier housing the bolt. The upper surface of the carrier immediately adjacent the front face includes a flat shelf for engagement with a charging handle. About the exterior of the bolt carrier are a series of lands and accompanying grooves, usually four, which extend from the forward end of the bolt carrier rearwardly over a distance of about one half the length of the bolt carrier. There are openings on the bolt carrier to mount a gas key, an opening which serves as a gas receiving port and an opening to receive the cam pin. Typically the gas key is secured to the bolt carrier through the use of two screws while the firing pin is retained in place through the use of a retaining or cotter pin.

Like the bolt carrier, the bolt has a body that is generally cylindrical in shape and is provided with a circular bore throughout its length which is designed to accommodate a firing pin. Located radially about a forward portion of the bolt are a series of lugs and an extractor. The exterior of the bolt has a recess provided therein with an extractor bearing surface that houses the extractor. The forward end of the extractor includes a gripping element, or claw, which catches and holds onto the rim of the case head of an ammunition cartridge.

The extractor rotates about a pin received by both the bolt body and the extractor. Located at the rearward end of the extractor is a spring and internal buffer. The extractor spring and buffer press against the extractor bearing surface thereby resisting rotation of the extractor about its axis and facilitate the extraction of a used ammunition cartridge.

Present on the front face of the bolt is an ejector that is located opposite the side of the front face adjacent the extractor. The ejector consists of a spring-loaded pin which is retained in place on the bolt through the use of a roll pin. The ejector assists in pushing an ammunition cartridge away from the bolt face when the firearm is being fired or otherwise unloaded.

The bolt carrier group is responsible for stripping, chambering, locking, firing, extraction and ejection of ammunition cartridges for the host rifle. The energy to perform these functions is provided in the form of hot, expanding gases which travel through the host firearm's gas tube, through the gas key and into the bolt carrier. A secure union between the gas key and bolt carrier is important to the proper operation of a direct gas operated firearm. Should the gas key become loose or be removed, the associated firearm will not properly function due to resulting gas leakage.

As shown in, the prior art method of attaching a gas key to the bolt carrier relies on two screws which are torqued and then staked in place.

illustrates a prior art bolt carrierwhich uses a separate gas keythat has an integral nozzle for communicating with the gas tube of the host rifle. The base of the gas keyis secured to the bolt carrierthrough the use of two retention screws. The retention screws are inserted through the openingslocated on the base of the gas keythen threaded into the openingslocated on the top surface of the bolt carrier. This method is deficient as the max torque applied to the screws is not sufficient to prevent the screwsfrom becoming threadedly unsecured due to vibration and the heating/cooling cycle of the host rifle during normal operation. The result is gas leakage which decreases the reliability of the host rifle by causing extraction and feeding related malfunctions.

The retaining pin or cotter pinfound in the prior art is retained within an openingthat provides no method to orient the pin. As a result the pincan be placed either by the user, or through rotation occurring during normal use of the rifle, into a position which orients the thinnest profile of the cotter pin towards the firing pin. This deficiency in the prior art reduces the service life of the cotter pinresulting in several critical issues. The cotter pin can become bent such that maintaining the rifle is difficult since the cotter pin should be removed to service the bolt and bolt carrier properly. Removing a bent cotter pinthrough the provided openingis difficult, often requiring tools such as pliers to accomplish. Once the cotter pinis removed, the user must be able to reinsert the cotter pinback into the openingof the bolt carrier. If the cotter pinis bent, this operation is often virtually impossible. The cotter pincan also break or bend sufficiently thereby rendering the rifle inoperable. The terms “cotter pin” and “retaining pin” are used interchangeably herein.

The prior art bolt has several points of deficiency. First, there are seven bolt lugs placed radially about the forward end of the bolt. These lugs are evenly spaced apart except for the gap created on the exterior of the bolt to accommodate the extractor, which gap is referred to herein as the extractor pocket. When the extractor pocket is machined, a portion of the bolt's face is removed, resulting in the case head of the cartridge not being fully supported (see).

Second, the lugs located on either side of the extractor pocket are not fully supported, rendering them the weakest lugs on the prior art bolt. As such, these two lugs experience the highest rate of failure. Further, the lugs themselves are machined with sharp edges or geometric corners about their exterior. These geometric corners often accumulate material stress which can result in micro fractures that limit the service life of the bolt.

Third, extraction of a spent cartridge by the extractor, extractor spring and buffer can be disrupted due to a variety of conditions including a fouled barrel chamber, an over pressured gas system, an improperly annealed cartridge rim, as well as others. To compensate for this deficiency, various remedies have been developed to include, for example, the use of o-rings which increase the force the extractor is capable of placing on the rim of an ammunition cartridge.

Fourth and fifth, problems persist with the present method of securing the gas key to the bolt carrier using two screws as described above, and with the method by which the cotter pin that retains the firing pin is able to rotate into a structurally weak position. Finally, there is a deficiency in prior art methods of manufacturing the bolt. It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.

In view of the foregoing, one object of the present invention is to overcome the shortcomings in the design of bolt carriers and bolts for self-loading firearms as described above.

Another object of the present invention is to provide a bolt carrier having an integral gas key with a removable nozzle which is constructed to be in communication with a gas tube of the host firearm.

Yet another object of the present invention is to provide a bolt carrier in accordance with the preceding objects in which the nozzle is threadedly secured to the gas key and held in place with a cross pin that relies on tension and the structure of the upper receiver to retain the cross pin in place.

A further object of the present invention is to provide a bolt carrier in accordance with the preceding objects in which the bolt carrier is constructed to orient the cotter pin that retains the firing pin such that the widest profile of the cotter pin is always oriented towards the firing pin.

A still further object of the present invention is to provide a bolt and bolt carrier in accordance with the preceding objects which includes a bolt with fully supported bolt lugs and an improved structure for incorporation of the extractor.

Another object of the present invention is to provide a bolt in accordance with the preceding objects in which the extractor engages a larger portion of the rim of the cartridge case as compared to prior art extractors.

A still further object of the present invention to provide an improved bolt carrier in accordance with the preceding objects that is not complex in structure and which can be manufactured at low cost but yet increases the reliability and safety of the firearm.

In accordance with these and other objects, the present invention is directed to a direct gas operated firearm of the AR15/M16 variety having an improved bolt carrier assembly. This improved bolt carrier assembly can be retrofitted to an existing direct gas operated AR15/M16 type rifle without the need for any modification to the receiver of the rifle or any other part thereof.

The improved bolt carrier includes an integral gas key which is threaded to receive an extension nozzle which is constructed to receive a portion of the host firearm's gas tube. The extension nozzle is held in place through the use of a cross pin which prevents loosening of the nozzle during use of the firearm.

The present invention also provides an improved bolt carrier that includes a machined structure on the exterior of the bolt carrier which optimally orients the cotter pin that retains the firing pin so as to maximize the service life of the cotter pin. In particular, the retaining pin is oriented in a vertical profile so that the widest profile of the retaining pin is always oriented toward the firing pin.

In addition, the improved bolt carrier according to one embodiment of the present invention has a bolt with a fully supported bolt face, eliminating the machining of a gap into the bolt face in order to accommodate an extractor. By fully supporting the bolt face, the lugs located on either side of the extractor pocket are not undercut, resulting in a more durable bolt.

Still further, one embodiment of the bolt includes an extractor having an extractor claw that grabs or engages approximately 17% more of an ammunition cartridge's rim as compared with prior art extractors. By spreading the forces related to extraction over a larger area of the rim of the cartridge, the likelihood of failed extraction is substantially diminished.

These together with other improvements and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being made to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

In describing a preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

The present invention is directed towards a bolt and bolt carrier group or bolt carrier assembly for use with the M4/M16/AR15 family of firearms and their derivatives. As used herein, the phrases “bolt carrier assembly” and “bolt carrier group” are used interchangeably.

Unless otherwise specified, the various components which make up the trigger mechanism, upper receiver assembly, lower receiver assembly, buttstock assembly, bolt and bolt carrier assembly are those found on the prior art M4 and M16 family of firearms.

As used herein, “front” or “forward” and “distal” correspond to the end of the bolt carrierwhere the gas key is located and nearest the muzzle of the firearm (i.e., to the left as shown in); and “rear”, “rearward”, “back” or “proximal” correspond to the end of the bolt carriernearest the buttstock of the firearm and opposite the end where the gas key is located (i.e., to the right as shown in).

As shown in, the present invention is directed to an improved bolt carrier assembly, generally designated by reference numeral, including a bolt carrierwith an integral gas key, a boltand an extension nozzlecoupled to the gas key with a roll pin. It will be understood that the bolt carrier assemblyis intended to be employed with any of the various direct gas operated M16 type firearms; however with minor modifications, some of its features could be more widely used for other firearms as well. The features of the boltare capable of being adapted to work with most direct and indirect (piston operated) gas operated firearms. It will also be understood that the bolt carrier assemblyis housed within an upper receiver, shown in, of a M16 type rifle.

As shown in the exploded view of the bolt carrier assemblyprovided in, and the isolated views of the bolt carriershown in, the integral gas keyis located on the top surface of the bolt carrier. The gas keyhas an openingat its rearward end for the roll pin, and a threaded openingat its front end which interfaces with a threaded memberon the extension nozzleas will be described more fully hereinafter. Horizontal side views of the bolt carriershown with the extension nozzlethreadedly retained in place and secured with the roll pinare provided in. The front end of the gas keyalso has an indexing notchthat is used to orient the extension nozzle as will also be described more fully hereinafter.

shows a cutaway view of the preferred embodiment bolt carrierwith the extension nozzle. An openingis machined into the top exterior of the gas block, through to the interior openingfor the bolt. The through bore created by the machining process is generally referred to herein as a port. The portis angled along its length and allows for the flow of expanding gases to pass from the gas keyinto the openingbehind the bolt, thereby facilitating the operation of the rifle.

Also present on the bolt carrieris a hammer clearance slot, which permits the hammer (not shown) to extend into the bolt carrierand strike a firing pin. An openingfor a cotter pinand an openingfor a bolt(shown in) are also provided within the bolt carrier.

show the openingdesigned to contain the cotter pin.

The cotter pin, also referred to as a retaining pin, is installed after the firing pinis placed within the interior of bolt carrier. The sole purpose of the cotter pinis to retain the firing pinwithin the bolt carrier. The openingis part of a bore which runs through the bolt carrier, perpendicular to the longitudinal axis thereof. The bore connected to the openingis constructed to accommodate the tail portionof the cotter pin. One end of the openingis constructed to hold the headof the cotter pinin a vertical orientation as shown in, thereby orienting the widest profile of the tail portiontowards the firing pin'sannular flange. From an external view, the openingabout the exterior of the bolt carrieris approximately “T” shaped. As seen best in, the vertical portion of the openingis for receiving the headportion of the cotter pin. The horizontal portion of the openingis to facilitate the insertion of a tool, such as a small screw driver, bullet tip, pliers or their equivalent, to aid in the removal of the cotter pin. By orienting the cotter pinin this manner, the widest profile of the cotter pinis oriented towards the rearward side of the annular flangelocated near the back end of the firing pin. This orientation with the largest profile of the cotter pinfacing the annular flangeof the firing pinmakes the cotter pinbetter able to resist metal fatigue which reveals itself as the bending or breakage of the part. It should be understood that in alternate embodiments the openingcould be oriented to have an external appearance such as an “X”, a “+”, or other equivalent shapes and structures, so long as the cotter pinis being oriented to expose the largest cross section of the tail portiontowards the annular flangeof the firing pinand prevent the cotter pinfrom unnecessarily rotating.

The openingin the bolt carrierfor the boltincludes a longitudinal bore which extends from the forward end of the bolt carrierrearwardly for a distance sufficient to accommodate the rearward portion of the bolt. A smaller bore(see) continues for a further distance to accommodate the rear endof the bolt. The top of the bolt carrierimmediately adjacent the front face thereof has a charging handle contact pointwhich facilitates manual operation of the host rifle.

Located rearwardly of the charging handle contact pointis a cam slotwhich provides a contained area for the cam pinto rotate, thus allowing the boltto move rearward and rotate axially within the bolt carrier. The cam pinretains the boltwithin the bolt carrier.

The bolt carrieris also provided with a series of bearing surfaces. These bearing surfacesare located on the front half, top and bottom sides of the bolt carrier, and are in direct contact with the interior of the upper receiver. The bearing surfaceslocated along the bottom portion of the bolt carrierare interrupted along there length by a series of sand cuts. The sand cutsare longitudinal cuts, having a generally rectangular shape, which reduce the exterior dimensions of the bolt carrier's bearing surfaceswhen present. If any foreign material, including material resulting from the discharge of a firearm, accumulates within the upper receiver, the sand cutsprovide an exit for the accumulating debris.

The bolt carrieris further provided with a series of flat surfacesmachined onto the forward portion of its exterior. These flat surfacesare present on both the right and left sides of the bolt carrierand machined so that they come to an apex. The apexat which point these flat surfacesmeet protrudes from the exterior of the bolt carrier. These “flats”provide additional space for the accumulation of debris. By providing space and egress points for the accumulation of debris, the static and kinetic friction forces between the bolt carrierand the interior of the upper receiverwill not increase as rapidly during prolonged use of the host firearm. Also present is a door openerwhich provides room for the door latch (not shown) to close.

As best shown in the isolated views in, the bolt carrier assemblyincludes an extension nozzlehaving an indexing notch, a threaded member, an openingand a port. Once the threaded memberof the extension nozzleis properly threaded with the threaded openingin the gas block, the roll pinis inserted through the openingin the gas blockand an openingthrough the extension nozzle thereby rotationally restraining the extension nozzle. The purpose of aligning the indexing notchesandis to ensure that the portof the extension nozzleis in communication with the portthrough the gas key(shown in) thereby facilitating the proper operation of the host firearm.

More particularly, a top perspective view of the extension nozzle is shown in, withbeing a bottom perspective view of the extension nozzle rotated 180 degrees about its longitudinal axis relative to the view shown in, making the gas portvisible.is a side perspective view of the extension nozzle rotated 90 degrees from the position shown in, making the openingfor the roll pinvisible. Finally,is a perspective cutaway view of the extension nozzle shown in, showing the opening through the extension nozzleand the gas port.

A timing washer, which is located between the extension nozzleand the forward face of the gas key, may be placed over the threaded memberof the extension nozzleand used as a means to orient the extension nozzlewhen it is threadedly secured to the gas block. More particularly, a series of wrench flatsare provided about the exterior of the extension nozzleand provide a means by which torque may be applied during installation of the extension nozzle. A crescent wrench or a wrench of similar design is used to rotate the nozzleby engaging with the wrench flats. When the extension nozzleis being threaded into the gas block, the indexing notchof the extension nozzleis aligned with the indexing notchof the gas key. The timing washer, which allows for a predetermined torque value to be applied, is selected during assembly to facilitate alignment of the two separate indexing marksandand application of the proper torque range. The timing washeris machined from stainless steel but other materials suitable for use in the manufacture of washers would also be acceptable. Alternatively, modern manufacturing techniques and technologies make it possible to time the threads, thereby eliminating the need for a timing washer.

Another method of securing the extension nozzleto the gas blockincludes press fitting them together. This can be achieved by manufacturing an extension nozzlewithout a threaded member and a gas block which has a non-threaded opening. The threaded portion of the threaded membershown in the illustrated embodiment would be replaced by a smooth exterior, shaped to be received by the non-threaded opening in the gas block. Such a non-threaded extension nozzle would need to be manufactured such that it required substantial force to be pressed into the opening of the gas block. Once pressed into place, the extension nozzle could then be further secured into place through the use of a roll pin such as roll pinor alternatively, welded.

The roll pinused to assist in securing the extension nozzleto the gas keymay, alternatively, be replaced with a non-tensioning type (i.e. dowel pin). This solution works because the gas keyof the bolt carrierrides in a channel(shown in) within the interior of the upper receiver. The location of the gas keywithin this channelretains the dowel or roll pin because there is insufficient space between the exterior of the gas keyand the walls of the channelfor the roll pinto fall out.

illustrates a perspective side view of a direct gas operated rifle, generally consisting of an upper receiver group and a lower receiver group. The lower receiver group, well known in the prior art, generally consists of a lower receiverwith internal operation control components, a buffer tube and buttstock. The upper receiver group generally consists of an upper receiver, a barrel, and a set of handguards, all well known throughout the prior art.

shows a side cutaway view of the upper receiverin which the channelin which the gas keyrides is visible. The channelis generally rectangular in shape and constructed to allow for the longitudinal travel of the gas keyand other attached components. The channelis narrow enough to prevent the roll pinholding the extension nozzlefrom falling out of the openingwhich is designed to house it. Thus the channel passively assists the roll pinin securing the extension nozzleonto the gas key.

shows a side cutaway view of the bolt carrierand extension nozzle. This view illustrates the gas tubeof the host firearm being received by and in operational contact with the opening at the forward end of the extension nozzle. In the illustrated embodiment, the opening at the forward end of the extension nozzlehas been provided with a 60-degree chamfer to ease its acceptance of the gas tube. When the rifleis discharged, gas travels through the gas tubeinto the openingof the extension nozzle, exiting the port(see) located at the rear of the extension nozzle, into the portwhich travels through the gas keyarriving at the rear portion of the opening, which houses the bolt, where the expansion of the gas causes the bolt carrierto move rearward. After a round of ammunition has been fired the bolt carrier groupis only able to move rearwardly when the chamber pressure of the barreldecreases sufficiently, thereby allowing the boltto rotate and disengage from the barrel extension (not shown).