AR Platform Firearm

Description

BACKGROUND OF THE INVENTION

The AR style firearm, sometimes called an AR-15, AR-10, AR platform firearm or modern sporting rifle, is popular and widely used in the United States. The AR platform has modular construction, and is highly customizable. The standard AR platform can be broken down and reassembled as desired, for convenient cleaning, transport and storage. Its main parts are a lower receiver group, which holds the lower receiver, a trigger assembly, a pistol grip, a magazine and a buttstock and buffer system; and an upper receiver group, which holds the upper receiver, a bolt carrier group, charging handle, gas system, a barrel, a handguard, and optional items like a rail system, free float handguards, precision barrels, and muzzle devices. The lower and upper receivers are both commonly made of 7075 aluminum alloy.

Spent cartridges fly out of the ejection port in a pattern that is not adjustable, and not always predictable, sometimes causing burns when hot brass touches the shooter's or their close companions' skin or gets caught in their clothing. Additionally, spent cartridges must be collected from the ground or floor after firing. A solution to make the spent cartridge trajectory controlled and more consistent and predictable would be desirable. A solution to catch spent cartridges would also be desirable.

Because the AR platform is designed to be strippable by a user with minimal tools, the various parts of the AR platform are generally connected using mechanisms that can easily be undone, such as sliding pins, nuts with flanges, notches or grooves with spring retention to secure a pin, slip fits, spring detents, and spring tension retainers. Other firearms have tighter connections that are more difficult to take apart. The AR platform connection mechanisms are inherently looser than other firearms even when brand new, and can become sloppy and less secure with use and wear. The resulting instability detrimentally affects a shooter's performance and accuracy during competitive shooting. This detrimentally affects long-distance marksmanship even more significantly.

The lower and upper receivers are attached with two pins (pivot/front and takedown/rear) which pass through holes in the aluminum alloy material of the upper and lower, and click into place. When the takedown pin is removed, the lower and upper can pivot out of assembled position, while still attached with the pivot pin. With repeated use, steel takedown pins attaching the lower and upper tend to erode and enlarge their receiving holes in the aluminum of the lower and upper receivers, making the attachment pivot points sloppy, and making it more likely that the lower and upper receivers become misaligned or even separate prematurely. A solution to prevent deterioration of the takedown and pivot pin/hole combination would be desirable. A solution to improve the solidity of the lower/upper attachment would also be desirable.

The barrel of an AR platform is attached to the upper with a slip fit barrel and barrel nut, which secures the barrel with a flange, rather than with pressure around the circumference of the barrel. This allows the barrel to rock and shift. A solution to enable a tighter barrel fit would be desirable. A solution to enable a taper fit barrel system would also be desirable, and would allow for a tighter barrel fit.

The direct impingement gas system of an AR platform firearm enables its semiautomatic capability, diverting some of the expanding gases from the explosion of the cartridge, and funneling gas through a gas block and gas tube back to the bolt carrier, which will eject the spent cartridge and cycle a new cartridge in. The slip fit gas tube is inserted into the gas block, and held in place with a roll pin. The difference in diameter between the tube and gas block hole can be 0.005 inches to 0.007 inches, allowing some of the gas and accompanying soot to leak and escape. A solution to prevent gas leakage would be desirable.

The recoil during firing of a traditional AR platform firearm causes the barrel to rise over the course of a burst of multiple shots. To counteract the inevitable rise of the barrel, a shooter begins by aiming low, so that the bullets “climb into the target.” A solution to reduce recoil is needed, allowing the shooter to aim flat, and achieve better accuracy.

The recoil also makes it difficult for the shooter to watch the bullet hit the target in real time, and requires the shooter to adjust the barrel back down in between every shot, which is detrimental in competitive or any form of rapid fire shooting. A solution to reduce recoil is needed.

The charging handle is used to pull the bolt carrier group backwards, inside of the upper receiver, to load or eject a cartridge manually. When pulling a conventional charging handle back, the straight back pulling motion naturally creates a moment in the charging handle, causing the front end of the charging handle to move upwards and scrape against the inside of the top of the upper receiver, creating friction and wear leading to a groove over time. A solution to prevent wear of the distal end of the charging handle against the inside of the upper receiver would be desirable.

After active pullback, and during firing, the charging handle can be undesirably and forcibly pushed out of and pulled into the upper by the bolt carrier. A common solution to this problem involves a latch, which keeps the charging handle in place inside the upper, but which must be actively released by the shooter by pulling a lever each time the shooter wants to use the charging handle. The latch mechanism can get stuck or caught or break during attempted pull-back of the charging handle. A better solution to keep the charging handle in place during firing is needed.

For a direct impingement gas system, a conventional gas key is bolted onto the carrier with two screws, and holds the charging handle. The gas key directs gas from the barrel and gas tube into the chamber in the bolt carrier. When gas cycles the bolt during firing, it applies shear force to the gas key, and thus its attachment screws, which can eventually shear off. One solution to this problem is a specialized one piece bolt carrier with gas key incorporated and not removeable. However, this doesn't allow for an anvil to be switched out with the gas key—in a gas piston system, an anvil is bolted onto the upper in the same location, and receives similar forces from the piston during cycling of the bolt. A solution to prevent shear force on the gas key/anvil attachment screws and to allow the same bolt carrier to be used in both direct impingement and piston operation would be desirable.

A handguard is commonly used, to enable the shooter to hold the front end of the firearm during firing, without being burned by the hot metal of the barrel and gas tube. Traditional free float handguards attach on one end with a pinch bolt clamping system, holding to the barrel nut. The remainder of the handguard extends forward, surrounding the barrel, but free-floating, and not touching the barrel. Force applied to the handguard, for example resting the handguard on a wall, can cause it to move and flex in relation to the barrel, so that the handguard and any attachments are no longer perfectly aligned with the barrel, and the accuracy of aim is lost. An improved handguard with a tighter fit and resistance to any movement would be desirable.

An AR platform is not designed for long distance accurate shooting. A solution to improve a shooter's long distance marksmanship, and assist in aiming, would be desirable.

BRIEF SUMMARY OF THE INVENTION

One solution to ameliorate the problem of takedown and pivot pin holes becoming sloppy, is to enlarge the takedown and pivot pin holes in both the upper and lower receivers, and insert press fit sleeves into the pin holes, to receive standard slip fit pins. An alternative solution, which also increases the solidity of the upper/lower receiver fit and connection, is to add a rail to the non-ejection side of the upper receiver, above the takedown location; remove the takedown pinhole from the upper receiver; and add a cam lever device which is mounted in the lower receiver's takedown pin location. The cam lever device has a shaft extending forward and upwards towards the rail on the upper receiver, with a cam lever on top of a latch that can releasably grab onto the upper rail, exerting increased downward force pulling the upper and lower together.

One solution to increase precision and toughness of the connection between the upper receiver and barrel is to use a two-piece upper. A traditional one-piece upper receiver is made of one material, including its snout to receive a barrel and barrel nut. A two-piece upper is mainly made of a first material, with a threaded barrel sleeve pocket at the breech end, instead of a snout structure. A tubular insert with threads on its outer surface is torqued into the upper's barrel sleeve pocket, forming a snout. This tubular insert can be made of stronger material than the upper receiver. It can also have a tapered inside surface, to enable a taper fit barrel system, which is an additional solution to strengthen and improve concentricity of the upper/barrel connection. A barrel with a tapered barrel extension is chosen and used to precisely mate with and fit into the two-piece upper.

Another solution to increase precision of the upper/barrel connection and alignment is to use a barrel alignment system. A barrel is typically aligned using a pin that slips into a slot in the upper receiver, and is then secured with a barrel nut. For an improved barrel alignment system, the slot is enlarged into a tapered rectangular notch, and the user inserts a barrel alignment washer, of the same shape and size as the notch, over the barrel alignment pin when installing a barrel.

A solution to improve the connection between the charging handle and bolt carrier during active pullback of the charging handle, as well as to reduce the friction between the charging handle and interior of the upper receiver during active pullback of the charging handle, is to add a mated undercut both to the portion of the bolt carrier that receives the end of the charging handle, and the end of the charging handle.

A solution to keep the charging handle in place after active pullback and during firing, while still allowing for convenient active pullback when desired, is to add a spring detent to the top surface of the charging handle head or neck area. A dimple is added to the interior surface of the upper receiver to receive the spring detent. This combination provides enough inertia to keep the charging handle in place during firing, and allows a user to actively pull back the handle without having to manipulate a latch each time.

A solution to gas leaks in a direct impingement gas system involves adding a ferrule to the gas block end of the gas tube, allowing the gas tube to be cinched into the gas block's gas tube hole.

A solution to improve precision of the gas block/barrel connection's precision is to add a notch to the gas block stop on top of the barrel, which mates with a key on the gas block itself, so that the gas block gas hole always sits azimuthally perfectly on top of the barrel primary gas hole. A combination of the gas block stop behind the gas block and a gas block jam nut in front of the gas block ensure that the gas block hole is in a translationally perfect position on top of the barrel primary gas hole.

A solution to strengthen the connection between a gas key or anvil and the bolt carrier, and to reduce shear forces acting on the bolts or screws which connect those components, is to add a rear wall to the perimeter of the gas key/anvil location on the bolt carrier, so that the wall absorbs much of the gas forces during firing. This is especially important when using an anvil, since the shear force on the anvil is much higher than on the gas key.

A solution to enable easy exchange of a direct impingement gas system and a gas piston system is to use a gas block with a gas tube hole that has the same elevation as the gas tube hole in the upper receiver that is threaded, enabling use of a straight gas tube. Anvil and gas key can be switched out of the walled gas key/anvil location on the bolt carrier, depending upon which gas system is preferred.

A solution to reduce recoil and allow the user to see where the bullets are hitting the target is to add a vent hole and tubular expansion chamber to the barrel, in front of the gas block. The expansion chamber covers the vent hole, and is held in place in back by the mating collar of a gas block jam nut and in front by an expansion chamber adapter. This combination of attachments also keeps the barrel in tension, which can improve accuracy.

Ability to adjust the weight and balance of an AR-platform firearm can be achieved by adding a handguard with removeable weights that fit into multiple pockets under the handguard. The weights can be configured for purposes such as reducing recoil, allowing faster followup shots in competition, and improving bipod balance,

A solution for a tighter fit of the handguard to the barrel, and to resist movement of the handguard in relation to the barrel, is to add a strong locking system to the breech end of the handguard, that locks to a standard barrel nut. Each of the multiple locks has a claw hook that reaches behind and around the barrel nut. By tightening the bolt in each lock, the claw hook is pulled backwards, robustly clamping the handguard to the barrel nut. This design enables longitudinal lock-up security on any traditional AR platform without requiring a proprietary upper receiver.

A solution to improve long distance marksmanship is to add a handguard extender. The handguard extender is generally shaped like a U-channel beam, and has internal longitudinal slots that can receive right, left and/or bottom rails on a handguard. The extender slip fits backwards onto the side and bottom rails of the handguard, which have high lubricity skid pads installed on the rails. When in a desired position, a locking pin can be inserted through one of several holes in the bottom of the extender, into the handguard, locking the handguard extender longitudinally in place. The bottom of the handguard extender can be an Arca rail, allowing easy attachment to a bipod which can now be placed some distance in front of the muzzle.

Another solution to improve long distance shooting capability is to use an upper receiver with offset Picatinny rail. The rear/buffer end of the Picatinny rail is slightly raised, so that the Picatinny rail slopes downwards toward the barrel. This angle allows for more use of the maximum adjustment of a scope, allowing for increased scope utilization for far-away targets.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an exploded right side view of an upper receiver, modular brass deflector and bolt.

FIG. 2 is an isometric view from the top, front and right side of an upper receiver with modular brass deflector installed.

FIG. 3 is a top view of the modular brass deflector shown in FIGS. 1 and 2.

FIG. 4 is an isometric view from the top, front and right side of the modular brass deflector shown in FIG. 3.

FIG. 5 is a right side view of the modular bass deflector shown in FIGS. 1-4.

FIG. 6 is an isometric view from the top, front and right side of a modular brass catch.

FIG. 7 is a top view of the modular brass catch shown in FIG. 6.

FIG. 8 is a right side view of the modular brass catch shown in FIGS. 6 and 7.

FIG. 9 is an isometric view from the top, front and right side of an upper receiver with modular brass catch installed.

FIG. 10 is a top view of the upper receiver with modular brass catch installed and shown in FIG. 9.

FIG. 11 is a right side view of the upper receiver with modular brass catch installed and shown in FIGS. 9 and 10.

FIG. 12 is a right side view of the upper receiver shown in FIGS. 1 and 2, with modular brass deflector installed, and attached at the pivot location to a lower receiver.

FIG. 13 is an isometric view from the top, rear and right side of the upper and lower receivers shown in FIG. 12.

FIG. 14 is an exploded isometric view from the top, front and right side of an upper receiver, showing sleeves for the takedown and pivot pinholes, and a takedown pin and pivot pin.

FIG. 15 is an exploded isometric view from the top, front and right side of a lower receiver, showing sleeves for the takedown and pivot pinholes.

FIG. 16 is an exploded top view of the same lower receiver and sleeves for the takedown and pivot pinholes shown in FIG. 15.

FIG. 17 is a close-up side view of a sleeve like those shown in FIGS. 14-16.

FIG. 18 is an isometric view of the sleeve shown in FIG. 17.

FIG. 19 is an isometric exploded detail view of the breech end of the upper receiver and sleeve shown in FIG. 14.

FIG. 20 is an isometric detail view of the upper receiver shown in FIG. 19, with sleeve installed in the pivot pinhole.

FIG. 21 is the same isometric view of the lower receiver shown in FIG. 15, here showing sleeves installed in the takedown and pivot pinholes.

FIG. 22 is the same isometric view of the upper receiver shown in FIG. 14, here showing a sleeve installed in the pivot pinhole.

FIG. 23 is a left side view of an upper receiver with a rail for use with a cam latch device.

FIG. 24 is a left side view of a lower receiver with a cam latch device in unlocked/extended position.

FIG. 25 is a left side view of the combined upper and lower receivers with cam latch shown in FIGS. 23 and 24.

FIG. 26 is an isometric close-up view from the top, rear and left side of the cam latch shown in FIGS. 24 and 25, with the cam lever and latch in locked/compressed position.

FIG. 27 is the same isometric view of the cam latch shown in FIG. 26, here with the cam lever and latch in unlocked/extended position.

FIG. 28 is an isometric view from the top, rear and left side of the combined upper and lower receivers with cam latch shown in FIG. 25.

FIG. 29 is a detail view of the cam latch shown in FIG. 28, with the cam lever and latch in unlocked/extended position.

FIG. 30 is a detail view of the cam latch shown in FIGS. 28 and 29, here with the cam lever and latch in locked/compressed position, grabbing onto the rail of the upper receiver.

FIG. 31 is an isometric exploded view from the top, front and right side of a two-piece upper receiver.

FIG. 32 is the same view of a two-piece upper receiver as shown in FIG. 31, here with upper insert installed.

FIG. 33 is a right side exploded view of an upper receiver with taper fit barrel system.

FIG. 34 the same right side view of an upper receiver with taper fit barrel system shown in FIG. 33, here with taper fit barrel installed.

FIG. 35 is a right side cutaway view of the upper receiver with taper fit barrel system shown in FIG. 34.

FIG. 36 is a side close-up view of a prior art straight barrel extension.

FIG. 37 is a side close-up view of the taper fit barrel extension shown in FIGS. 33-35.

FIG. 38 is a top view of an upper receiver and barrel with barrel alignment washer.

FIG. 39 is a top detail view of the upper receiver breech end, barrel nut, barrel alignment washer and pin, and breech end of the barrel shown in FIG. 38.

FIG. 40 is an isometric detail view from the top, front and right side of the same area and elements shown in FIG. 39.

FIG. 41 is a top close-up view of a barrel alignment washer.

FIG. 42 is an isometric close-up view showing the top, front and left side of a barrel alignment washer.

FIG. 43 is an isometric view showing the top, front and right side of a charging handle and bolt carrier group.

FIG. 44A is a right side view of the charging handle and bolt carrier group shown in FIG. 43.

FIG. 44B is a right side detail view illustrating the mated undercuts of the charging handle and bolt carrier.

FIG. 45 is a top view of the charging handle and bolt carrier group shown in FIGS. 43 and 44.

FIG. 46 is a top detail view of the detent located on the neck of the charging handle shown in FIGS. 43-45.

FIG. 47 is a top view of an upper receiver with charging handle installed inside.

FIG. 48 is a right side view of the upper receiver with charging handle shown in FIG. 47, with the top portion of the upper receiver cut away to show a cut view of the charging handle and detent, along line A of FIG. 47.

FIG. 49 is a side cutaway detail view of the charging handle detent, engaged with an indent on the inside of the top portion of the upper receiver.

FIG. 50 is an isometric view from the top, front and left of a bolt carrier, showing the walled gas key location.

FIG. 51 is a top view of the bolt carrier of FIG. 50.

FIG. 52 is a top view of a prior art bolt carrier, without a wall.

FIG. 53 is a top view of a bolt carrier with mounted anvil.

FIG. 54 is a left side cutaway view of the bolt carrier with mounted anvil shown in FIG. 53, cut along line A of FIG. 53.

FIG. 55 is a left side view of the bolt carrier and anvil of FIGS. 53 and 54.

FIG. 56 is a left side cutaway view of the bolt carrier with a mounted gas key, cut along line A of FIG. 53, with a gas key replacing the anvil.

FIG. 57 is a left side view of the bolt carrier with mounted gas key.

FIG. 58 is an isometric close-up view from the rear, top and right of a gas key.

FIG. 59 is an isometric close-up view from the rear, top and right of an anvil.

FIG. 60 is a right side view of the anvil shown in FIGS. 53, 54, 55 and 59.

FIG. 61 is an isometric close-up view from the rear, bottom and right of the anvil of FIGS. 59-60.

FIG. 62 is a top view of an upper receiver and barrel with leak-proof gas system installed.

FIG. 63 is a right side view of the elements shown in FIG. 62, with the gas block shown cut away.

FIG. 64 is the same top view shown in FIG. 62, with the front end of the gas tube removed, and the gas block shown cut away, to show the key of the gas tube fitting into the notch on the gas block journal stop.

FIG. 65 is the same right side view of the elements shown in FIG. 63, with barrel and gas system elements shown exploded.

FIG. 66 is a right side close-up view of the straight gas tube with ferrule, and gas block.

FIG. 67A is an isometric close-up view from the rear, bottom and right side of the gas block.

FIG. 67B is a top detail view of a barrel, showing the gas block stop notch.

FIG. 68 is an isometric close-up view from the front and side of the gas block jam nut.

FIG. 69 is a top view of an upper receiver and barrel with gas piston system installed.

FIG. 70 is a right side view of the elements shown in FIG. 69, with the gas block jam nut loosened and moved forward, to show threading on the barrel in front of the gas block.

FIG. 71 is the same right side view of the elements shown in FIG. 70, with the gas block jam nut in its tightened position, and showing the gas block and front end of the gas piston system cut away.

FIG. 72 is the same right side view of the elements shown in FIG. 70, with the barrel and gas piston system elements shown exploded.

FIG. 73 is a top view of an upper receiver and barrel with expansion chamber installed, and part of the expansion chamber shown cut away.

FIG. 74 is a top close-up view of the expansion chamber and barrel.

FIG. 75 is a right side view of the same elements shown in FIG. 73.

FIG. 76 is a top view of an upper receiver and barrel, with the expansion chamber, muzzle nut and muzzle brake shown exploded.

FIG. 77 is a right side view of the elements shown in FIG. 76.

FIG. 78 is a rear view of an area handguard and several unattached weights.

FIG. 79 is an isometric view from the top, rear and right side of an area handguard and four unattached weights.

FIG. 80 is an isometric view from the bottom, front and right of an area handguard with four weights attached underneath.

FIG. 81 is a bottom view of an area handguard with 4 unattached weights.

FIG. 82 is a right side view of an upper receiver and handguard, attached with claw hook locks.

FIG. 83 is a right side view of the elements shown in FIG. 82, with bolts loosened from the claw hook locks.

FIG. 84 is an isometric detail view from the top, front and right side of components of the handguard claw hook lock assembly shown exploded.

FIG. 85 is a side detail view of the handguard claw hook lock assembly situated under the barrel, shown exploded.

FIG. 86A is an isometric close-up view of a first version of a claw hook.

FIG. 86B is an isometric close-up view of the claw hook shown in FIG. 86A, shown from an alternative angle.

FIG. 87A is an isometric close-up view of a second version of a claw hook.

FIG. 87B is an isometric close-up view of the claw hook shown in FIG. 87A, shown from an alternative angle.

FIG. 88 is an isometric close-up view of a washer for use with the claw hook lock assembly.

FIG. 89 is a top view of an upper receiver, barrel, handguard and handguard extender.

FIG. 90 is a right side view of the elements shown in FIG. 89, plus a pin, with a portion of the handguard extender shown cut away.

FIG. 91 is a bottom view of an upper receiver, handguard and handguard extender.

FIG. 92 is a right side detail view of the handguard and handguard extender.

FIG. 93 is an isometric view from the bottom of the handguard, handguard extender and pin.

FIG. 94 is a front view of the handguard and handguard extender.

FIG. 95 is an isometric view from the top, front and right side of an upper receiver with sloped Picatinny rail.

FIG. 96 is a side view of an upper receiver with sloped Picatinny rail.

DETAILED DESCRIPTION OF THE INVENTION

Improvements to the standard AR platform firearm are herein described. Certain terms are used which are defined herein:

A spent, empty bullet casing may also be called brass, shell, case, casing.

The upper receiver may be called the upper.

The lower receiver may be called the lower.

The bolt carrier group may be called the BCG.

The front end of a barrel or other part associated with the barrel may be called the muzzle end, and the back end may be called the breech end.

The front end of an upper receiver or other part associated with the upper receiver may be called the snout end or breech end, and the back end may be called the buffer end.

The front pin of the two pins holding the upper and lower receivers together may be called the pivot pin, and is located at the pivot location.

The rear pin of the two pins holding the upper and lower receivers together may be called the takedown pin, and is located at the takedown location.

The terms “user” and “shooter” are used to describe a person who uses the firearm and improvements thereto.

Modular Brass Deflector

FIGS. 1-5 and 12-13 show a modular brass deflector which can be changed and removed by a user. FIGS. 1, 2, 12 and 13 show the ejection side 8 of an upper receiver 1, with the buffer end 3 on the left and breech end 2 on the right. The modular brass deflector 11 is attached to the upper receiver 1 allowing a different trajectory of the spent brass than the conventional upper. By having an easy to install system, the user can select from a set of modular brass deflectors based on the desired trajectory. The trajectory of the brass is determined by the physical shape of the modular deflector.

To enable attachment of the modular brass deflector, the manufacturer creates a hole 6 through the top of the brass deflector portion 4 on the ejection side 8 of the upper receiver 1, as shown in FIG. 22. This hole 6 can be threaded to receive a screw, or have an interior surface appropriate to receive a slip-fit and pin, or be configured to receive another type of connection. A modular brass deflector 1 can be installed by the user on top of the upper's case deflector portion 4, as shown in FIGS. 1 and 2, for example with a screw 10. The connecting portion 13 includes the back end 16 of the modular brass deflector, has a bolt hole 12, and is shaped (see FIGS. 3, 4 and 5) to hug the shape of the top surface 5 of the upper's brass deflector 4 at and near the bolt location 6. A deflecting portion 14 includes the front end 15 of the modular brass deflector, and extends forward and above a rear portion of the ejection port 7, with its inner edge 17 securely coupling along the outer surface of the upper 1, above the ejection port 7.

After firing, spent cases are extracted and ejected by the bolt carrier. Upon ejection, cases travel backwards, impact the brass deflector 4, 11 and change trajectory. The standard trajectory, caused by the standard brass deflector portion 4 of the upper receiver 1, located behind the ejection port 7, is not well controlled or in an ideal direction. The modular brass deflector 11 can change the trajectory to a more consistent and desired location. This is done by changing the physical shape of the deflector structure. The physical shape can include a curved inner surface 18 and a top barrier 14 as shown in FIGS. 3, 4 and 5. The physical shape is profiled to cause an ejection direction.

In a preferred embodiment, the threaded hole 6 in the upper receiver's brass deflector portion 4 is drilled to accommodate a 12 inch 10-32 button head cap screw 10, which is used to attach the modular brass deflector 11 and modular brass catch 20 described below. The improved brass deflector 11 can be made of the same material as the upper receiver 1, for example 7075 aluminum alloy, and is usually made to match the look of the upper 1. A user can easily switch between brass deflectors of different shapes, colors, materials, sizes, angles, intended trajectories, etc. by removing and re-attaching an improved brass deflector of choice. Alternatively, a user can attach a modular brass catch, see below.

Modular Brass Catch

As an alternative to the modular brass deflector, FIGS. 6-11 show a modular brass catch 20 which can be installed and removed by a user. FIGS. 6, 7 and 8 show different close-up views of the modular brass catch. FIGS. 9, 10 and 11 show the ejection side 8 of an upper receiver 1, with the buffer end 3 on the left and the breech end 2 on the right. The attachment method and location for the modular brass catch 20 is the same as that for the modular brass deflector 11. The manufacturer creates a hole 6 through the top of the brass deflector portion 4 of the upper receiver 1, to accommodate an intended fastener. This hole can be threaded to receive a screw, or have an interior surface appropriate to receive a slip-fit and pin, or be configured to receive another type of connection. A modular brass catch 20 can be installed by the user with a screw 10 through the modular brass catch hole 21 in the connecting portion 22, as shown in FIGS. 9 and 10. In a preferred embodiment, the holes 6, 21 are created to accommodate a 12 inch 10-32 button head cap screw.

When attached as shown in FIGS. 9, 10 and 11, the adaptor portion 23 of the modular brass catch surrounds the top and front edges of the ejection port 7. The modular brass catch's “roof” portion 28 extends along and above the horizontal top edge of the ejection port 7, with the modular brass catch's inner/receiver edge 26 securely coupling along the body of the upper receiver 1. At the front end 24 of the roof portion 28, the modular brass catch adaptor structure 23 bends downward to extend along and in front of the front edge of the ejection port 7, still securely coupling its inner/receiver edge 26 along the body of the upper receiver 1. The shape of the adaptor portion can vary, and is profiled to direct spent cartridges in a collection direction.

The entire modular brass catch 20 fits below the Picatinny rail 180, and can be attached as shown in FIGS. 9, 10 and 11 with a clip 29 at its front end 24 to the Picatinny rail 180. The modular brass catch structure creates a barrier, with its undersurface 27 preventing spent cartridges from flying backwards, upwards or forwards, instead directing them outwards and downwards.

In a preferred embodiment, the modular brass catch roof portion 28 extends outwards from the upper receiver 1 about ¾ inch, and the roof portion 28 is approximately 2.9 inches long. At the front edge of the ejection port 7, the “front wall” portion 24 of the modular brass catch extends at a 90 degree angle downwards, its inner edge 26 hugging the body of the upper receiver 1, to a point ahead of and slightly below the front edge of the ejection port 7.

A container, bag or tube can be attached to the modular brass catch adaptor portion 23 to collect the spent cartridges. A user can easily switch out one modular brass catch for another, or for a modular brass deflector.

Sleeves for Pivot and Takedown Pin Locations

FIGS. 12 and 13 show combined lower and upper receivers 37 connected at the pivot pin and open at the takedown location. FIGS. 12-22 show takedown 32, 36 and pivot pinholes 31, 35 on the lower 30 and upper receivers 1, with sleeves 33 to receive the steel pivot and takedown pins 34. The sleeved holes are designed to increase the strength and durability of the pivot and takedown connections on the AR platform. The sleeves can be made of tougher materials, allowing for a more robust fit with better longevity.

Shown in FIG. 14, pivot and takedown pins 34 have a standard size with an outer diameter of 0.250 inches. Standard takedown and pivot pinholes in the lower and upper receivers have an inner diameter of between 0.251 and 0.257 inches, to allow a removable slip fit. Sleeved pinholes can be manufactured with an inner diameter slightly greater than the standard inner diameter, and a groove 39 on one end. Shown in FIGS. 12, 13, 14 and 22, the upper receiver 1 has one pivot pinhole 35 and one takedown pinhole 36. Shown in FIGS. 12, 13, 15, 16 and 21, the lower receiver 30 has two pivot pinholes 31 and two takedown pinholes 32. A gunsmith or manufacturer installs tubular sleeves 33 of appropriate lengths to fit into each pivot 31, 35 and takedown pinhole 32, 36. These sleeves 33, shown close-up in FIGS. 17 and 18, have an inner diameter similar to the conventional takedown and pivot pinholes, to allow for a removable slip fit for standard pivot and takedown pins 34, and an outer diameter to mate with the inner diameter of the improved pinholes, and a lip 38 having a shape and size to mate with the groove 39 of the improved pinholes, to allow for a precise tight press fit of each insert, as shown in FIGS. 19 and 20. FIGS. 21 and 22 show the sleeves 33 installed into the pinholes of the upper 1 and lower receivers 30.

In a preferred embodiment, the pinholes are manufactured with an inner diameter of 0.288 inches and a groove on one end with 0.305 inch inner diameter and 0.020 inch height of the groove. In this preferred embodiment, the sleeves are made of steel and have an inner diameter of 0.251 or 0.252 inches, an outer diameter of 0.288 inches, and a lip having an outer diameter of 0.305 inches and a length of 0.020 inches. These measurements are an example of a preferred embodiment, not intended to limit the invention, and can be altered by the manufacturer as desired, still being within the scope of the invention.

A user can assemble and disassemble the sleeved AR platform firearm using standard takedown and pivot pins 34. The resulting steel on steel connection is much more durable than standard aluminum on steel connection.

Cam Latch Upper/Lower Connection Device

The connection between upper 1 and lower receivers 20 in the takedown pin area can be made sturdier, tighter and more secure with a cam latch device 44, shown in FIGS. 23-30. This device is used in place of the rear takedown pin, and extends from the takedown pin location 32 on the lower 30 to a rail 40 installed on the upper 1 as shown in FIG. 23, effectively pulling the upper 1 and lower 32 together as shown in FIGS. 25 and 28. The device has a latch 48 which is configured to grab or bite onto the rail 40, and when the cam lever 49 on top of the latch 48 is locked 51 as shown in FIGS. 26 and 30, the device strongly pulls the upper 1 against the lower 30. The direction of the cam lever 49 determines the downwards and backwards partial forces exerted by the device. The device has a tension adjustment that the user can set to a desired amount of force.

Instead of a standard removable steel takedown pin, the cam latch device 44 is installed at the standard takedown location 32 in the lower receiver 30, as shown in FIGS. 24, 25 and 28, using a mounting structure 45. A mounting structure pin 46 is inserted at the standard takedown pin location 32, passing through both sides of the lower receiver and held in place with a detent pin (not shown), with a portion of the pin protruding from the non-ejection side 43 of the lower receiver 30. A mounting structure rod 47 is attached to the protruding portion of the pin on a first end of the rod, with a latch 48 and cam lever 49 attached to the second end of the rod 47. The rod 47 extends diagonally forwards and upwards, with the latch's bottom edge 48 being perpendicular to the axis of the rod 47 and facing towards the upper receiver 1, and the cam lever 49 on top of the cam lock 44 as shown. In a preferred embodiment, the angle of inclination of the rod 47 can be 60 degrees from horizontal. The angle of the latch's bottom edge 48 can be perpendicular to the angle of the rod 47, and so in this example, would be 30 degrees from horizontal when installed as shown. The angle of inclination of the rod can range from 30 degrees to 90 degrees from horizontal.

The upper receiver 1 according to this invention does not have a takedown pinhole. Instead, a straight rail 40 is built on the non-ejection side 42 of the outer surface of the upper 1, starting at a point on the non-ejection side 42 surface of the upper 1 which is above and slightly behind the position 36 of where a takedown pin would normally be placed, and extending diagonally forwards and downwards across the non-ejection side surface of the upper. The rail's angle of inclination matches that of the cam latch's bottom surface 48, in a preferred embodiment being 30 degrees from horizontal. The angle can range between 0 degrees and 50 degrees from horizontal for an effective latch hold. The rail 40 can have a gap 41 which is configured to receive the inner side of the rod 47.

When a user pivots the upper 1 and lower receivers 30 on the pivot pin (see 34 in FIG. 25) to a closed position, the cam lever 49 should be in the open position 50 shown in FIGS. 24, 25, 27, 28 and 29, such that the latch's bottom edge 48 is positioned above the rail 40. The user then pivots and pushes the cam lever 49 to its closed position, see FIGS. 26 and 30, which pushes the latch 48 slightly downwards along the rod 47, and the bottom edge of the latch 48 securely latches onto the rail 40, securing the upper receiver 1 tightly to the lower receiver 30.

To detach the upper 1 and lower receivers 30, the user pulls and twists the cam lever 49 into its open position 50, which releases the latch 48 from the rail 40, allowing the upper and lower receivers to open and pivot apart on the pivot pin 34.

Note that while in a preferred embodiment, the latch bottom edge 48 is perpendicular to the rod, other configurations of rod, latch bottom edge and rail can be effective and still be within the invention described herein. For example, if the rod is not perpendicular to the rail, then the latch bottom edge will have a different angle in relation to the rod, in order to match the angle of and be able to grab onto the rail.

As shown in FIGS. 23-25 and 28-30 and described, the cam latch device 44 and rail 40 are installed on the left side of the receivers, opposite to the ejection port, which is traditionally on the right side. For a left-handed firearm, the cam latch device 44 and rail 40 would be installed on the right side, opposite the ejection port which would be on the left side.

Upper Insert for Enhanced Connection Between Upper Receiver and Barrel (Two-Piece Upper)

A traditional upper receiver is one piece made of aluminum alloy, including a snout for receiving a barrel. FIGS. 31 and 32 show an upper insert 61 which is added to a barrel sleeve pocket 59 on the breech end 2 of the upper receiver 1 by a manufacturer or gunsmith, creating a snout structure. The resulting improved two-piece upper 66 (also shown in FIGS. 9-14) features a threaded barrel attachment point 62 that can be made of a different material from the rest of the upper receiver 1, allowing for a stronger barrel connection.

The upper insert 61 can be made of tubular steel having a non-standard internal profile. For example, the internal profile can have an inner diameter taper, with the barrel/muzzle (front) end 63 being the wider end. A torquing mechanism can be added to the sleeve for installation, for example such as notches 65 or holes for a spanner wrench. In a preferred embodiment, the upper insert 61 is about an inch long, and has an inner diameter taper of 2 degrees all around, which translates to a 0.06984 taper ratio. A portion of the outer surface, starting at the front end, is threaded to accommodate later use with a barrel nut. The rear portion 64 of the outer surface 62 can be threaded as shown in FIG. 31, or other structures and methods can be used for attachment to the upper breech end 70.

To install, the manufacturer applies threadlocking compound and twists the insert into the upper receiver barrel sleeve pocket 59, torquing securely for example with a spanner wrench. This procedure would be performed before installing the feed ramp into the upper receiver. With the upper insert installed as shown in FIG. 32, the snout area of the upper receiver is now strong enough to support a taper fit barrel, and can alternatively provide a more precise and solid lock-up when using a barrel nut to attach the barrel.

Taper Fit Barrel System

To enable a taper fit barrel which is perfectly centered with the bore axis 71, an upper insert 76 must be installed into the barrel attachment point 2 of the upper receiver 1 as shown in FIGS. 33, 34 and 35, forming a taper sleeve 76. The barrel 70 has a taper fit barrel extension 77 at the breech end 78. Compare the taper fit barrel extension 77 shown in FIG. 37 to a prior art barrel extension 80 shown in FIG. 36, which is not tapered. The tapered upper insert 76 has a taper angle that mates with its paired taper fit barrel extension 77, ensuring a quality conical mate.

The taper fit barrel extension 77 can be made of steel, with a slightly conical outer surface shape, increasing in outer diameter from 78 breech to muzzle, and a flange 79 on the muzzle end; and an alignment pin 86 (shown in FIGS. 38-40) on the outer surface on the breech end 78 near the flange 79. In a preferred embodiment, the distance between breech end 78 and flange 79 is approximately 1¼ inches. In a preferred embodiment, the flange 79 has an outer diameter of 1 3/16 inches.

The combination of two-piece upper 66 (taper sleeve 63, 76) and mated taper fit barrel extension 77 allow a secure, perfectly centered fit and bore.

Barrel Alignment Washer

When attaching a barrel 70 to an AR platform upper receiver 1, a traditional round barrel alignment pin 86 slip-fits into a rectangular notch in the barrel nut 84 which is attached to the breech end 2 of the upper receiver 1, facilitating alignment of the barrel's gas hole 132 with the gas tube hole 126 in the upper as shown in FIG. 38. Perfect alignment and centering is important for proper fitment of the gas tube 136 (shown in FIGS. 62-65) or gas piston kit 145 (shown in FIGS. 69-73 and 75-77). Imperfect alignment decreases reliability and potentially can damage the gas system.

To improve the fit, centering and security of the barrel alignment pin 86, the rectangular notch is enlarged and tapered 85, and a tapered square washer 87 is added, as shown in FIGS. 38, 39 and 40. The washer 87 is shown close-up in FIGS. 41 and 42. The washer 87 can be tapered and narrower on its breech end 88, and square and wider on its muzzle end 89, as pictured in the Figures. The washer 87 enlarges the surface contact of the barrel alignment pin 86, aiding in alignment and relieving stress on the upper receiver contact point, as shown in FIGS. 39 and 40.

When buying an improved barrel alignment system, the user receives an upper receiver with enlarged notch 85 on a barrel nut 84, and a separate barrel alignment washer 87 to be used when attaching a barrel 70.

Positive Engaging Charging Handle/Bolt Carrier Group Assembly

The charging handle 90 is used to open the action, pulling the bolt carrier group 100 back to its rear position. A user pulls the handle 91 to insert a round into the chamber of the firearm. The distal end 95 of the charging handle 90 extends downwards, to grip the end of the bolt carrier 101. Traditionally, the shaft 94 and distal end 95 of the charging handle 90 is L-shaped, with the shaft being horizontal, and the inner surface of the distal end of the charging handle being a flat vertical segment, which presses against a flat vertical surface of the end of the bolt carrier group.

In a positive engaging charging handle/bolt carrier group assembly 100 shown in FIGS. 43, 44A and 44B, the distal end 95 of the charging handle 90 is undercut, see 96 in FIG. 44B, and the end 103 of the bolt carrier 101 is shaped with a mated undercut 103 to securely receive the undercut distal end 96 of the charging handle 90. This positive connection prevents slipping and misalignment of the charging handle's distal end 95, 96 and the bolt carrier 101, 103, which in turn prevents the distal end 95 of the charging handle 90 from pivoting upwards and scraping against the inner surface 9 of the upper receiver 1, as shown in FIG. 48.

In a preferred embodiment, the hook 96 on the charging handle's distal end can be a reverse dovetail or birdbeak shape, with a 45 degree angle and extension of 1/16 inch. The undercut area 103 on the bolt carrier 101 can also be seen in FIGS. 54-57.

Charging Handle Detent

A spring detent 97 is installed on the top surface of the neck 93 of the charging handle, which mates with an indent (or dimple) 125 on the interior surface 9 of the top part of the upper receiver 1, as shown in FIGS. 45-49. FIGS. 45, 46 and 48 illustrate the preferred location of the detent 97 on the neck 93 of the charging handle. FIG. 47 shows the top of the upper receiver 1, with charging handle 90 inserted, illustrating the cutaway line A for FIGS. 48 and 49. The location of the indent or dimple 125 in the underside of the top part of the upper receiver 1, to receive the charging handle detent 97, can be seen in FIG. 48.

The detent/indent combination holds the charging handle 90 in place during normal fire, so that the charging handle 90 does not move in and out with the bolt carrier 101. The detent/indent combination releases when the user actively pulls back on the charging handle, and so no latch mechanism needs to be released every time.

Bolt Carrier with Walled Gas Key

In a direct impingement gas system, the gas key 111 directs gas from the barrel 70 and gas tube 136 into the upper receiver 1, forcing the bolt carrier group 100 backwards. The gas key 111 is attached to the top surface of the bolt carrier 101 with bolts or screws, and during cycling, the gas key structure 111 travels within the long segment 94 of the charging handle 90. The gas from each shot transfers kinetic energy, directed backwards 110, through the gas tube 136 to the gas key 111 to the entire bolt carrier group 100, placing high shear forces 110 on the two screws (see gas key screw holes at 112 and bolt carrier screw holes at 105 in FIGS. 50-52, 56 and 57) that anchor the gas key 111. FIG. 52 shows a prior art bolt carrier 104, where the gas key 111 is mounted on the flat, smooth top surface of the bolt carrier, without any structure added 108 to relieve the screws from the shear forces 110 caused by the gas and bolt (not shown) traveling backwards into the bolt carrier at its front end 109. Note that a flat plane for the gas key is traditionally machined onto a prior art bolt carrier, see FIG. 52, and the flat plane continues behind the gas key 111 (see item 108).

The bolt carrier 101 with walled 107 gas key 111 shown in FIGS. 56 and 57 adds new structural elements both to the gas key 111 itself, and to the portion of the bolt carrier that receives the gas key. As shown in FIGS. 50, 51, 55 and 56, a wall 107 is left on the upper surface of the bolt carrier 101 when machining out the flat location for the gas key, for the purpose of allowing the gas key 111 to nest against the wall 107. The added wall 107, shown in FIGS. 50, 51, 54 and 55, absorbs much of the gas forces 110 during cycling, relieving stress on the two gas key screws which attach through the gas key holes 112 into the bolt carrier holes 105, and transferring the force 110 directly to the structure of the bolt carrier. The gas key 111, shown in FIGS. 56, 57 and 58, is shaped to fit into the new position, with its rear edge 115 firmly fitting against the rear wall 107. This prevents failure of the gas key screws, and extends the life of the gas key/bolt carrier connection.

The new gas key position can have a lip 121 as shown in FIG. 50 extending around both sides and the rear 115 of the gas key 111 when installed and seated against the wall 107. The modified bolt carrier with a walled gas key also allows for the use of a bolt-on anvil 116, used in piston setups. In previous bolt carriers, the strong force caused by the piston impacting the anvil more quickly shears the gas key/anvil screws, making it difficult to successfully convert a bolt carrier from direct impingement gas system to gas piston system. With the walled carrier and enhanced anvil, a piston operation is possible.

The dimensions of the wall and lip vary, based on the curvature of the bolt carrier before machining, and the top edge of the wall can be an arc. In a preferred embodiment, the highest section of the wall can be 0.723 inches from the flat portion of the gas key location, and the lip on the sides of the gas key location is shorter.

Improvements for Leak-Proof Gas System

Standard methods for attaching the gas block 130 to the barrel 70 include pins, set screws coupled with dimples in the barrel, or a clamp. Gas leakage is very common with these setups. The set screws eventually move around, away from the dimples, misaligning the gas block's gas hole 143 with the barrel gas hole 132. A slip fit between the gas tube 136 and gas block's gas tube hole 144 also allows for gas leakage.

For a leak-proof gas system, as shown in FIGS. 62-65, improvements are made to the barrel 70, gas block 130 and gas tube 136, and a gas block jam nut 131 is added. Threading 73 is added to the outer surface of the barrel 70 in front of the primary gas hole 132 (towards the muzzle end), as shown in FIG. 70, to receive a gas block jam nut 131, in front of the gas block 130. The gas block jam nut 131, shown in FIGS. 62-65 and close-up in FIG. 68, is torqued on in front of the gas block 130. This holds the gas block 130 in place from the front/muzzle end, while the gas block stop 83 holds the gas block 130 in place from the rear/breech end, holding the gas block 130 in an axially perfect position. A notch is added to the stop 83, to receive a key 134 from the gas block 130, to keep the gas block in an azimuthally perfect position. Together, the gas block jam nut 131, gas block stop 83 and notch combined with gas block key 134 hold the gas block 130 in place precisely over the primary gas hole 132.

The gas block 130, shown close-up in FIG. 67A, includes a key 134 (also shown in FIG. 64), to fit in the notch of the gas block stop 83, shown in FIG. 67B. Also, the gas block 130 is taller than a standard gas block, to enable placement of the hole 144 which receives the gas tube 136 to be at the same elevation as the gas hole 126 in the upper 1, enabling use of a straight gas tube 136 (see FIG. 63). Traditional bent gas tubes are a remnant of old AR platform design, to accommodate the shape and size of prior art handguards.

The leak-proof gas system includes a straight gas tube 136, without the standard bend. A ferrule 137 is added to the point of connection 138 between the gas tube 136 and the gas block 130, as shown in FIG. 66, rather than a bare slip fit. The gas block's gas tube hole exit 144 is internally threaded, to receive the threaded gas block end 138 of the gas tube. Upon tightening, the ferrule 137 cinches onto the gas tube 136, creating a leak-proof system.

Interchangeable Direct Impingement Kit and Piston Kit

An alternative to a direct impingement (DI) gas system is a gas piston system. Normally, a gunsmith or manufacturer installs either a direct impingement system or a piston system. With the AR platform improvements described herein, a piston kit 145 as shown in FIGS. 69, 70, 71 and 72 can be freely switched out with a direct impingement system by the end user.

The straight line of the gas block 130 to the upper gas hole 126 allows for a standard DI or piston setup. The threaded ferrule design can be backed out allowing for the installation of the piston setup. This allows for an easy change/upgrade between gas systems.

Components of the leak-proof gas system and bolt carrier with walled gas key described above enable easily interchangeable DI and piston kits. The taller gas block 130, enabling a straight line between gas block 130 and gas key 111/anvil 116, is ready-made to accommodate a piston setup. There is no need to loosen or remove the gas block 130 during the switching process.

To switch from the leak-proof gas system, the user removes the bolt carrier 101 from the upper 1, removes the gas key 111 from the bolt carrier 101, and installs an anvil 116 with bolts passing through the anvil bolt holes 118 into the bolt carrier bolt holes 105, staking them in. Then the user removes the handguard, loosens the gas tube ferrule 137 with a wrench, slides the gas tube 136 backwards into the upper 1 gas tube hole 126, releasing its front end 138 from the gas block, and then slides the back end 139 of the gas tube 136 forward out of the upper 1 and gas key gas tube hole 114, removing it. The user then slides the piston system 145 into the upper gas tube hole 126, tightens the piston snout onto the gas block's gas tube hole 144 with a wrench, slides the piston onto the piston snout, inserts the bolt carrier 101 into the upper 1, and replaces the handguard.

To switch from piston system to gas system, the user removes the bolt carrier 101 from the upper 1, removes the anvil 116 from the bolt carrier 101, and installs a gas key 111 with bolts passing through the gas key bolt holes 112 and bolt carrier bolt holes 105, staking them in. Then the user removes the handguard, loosens the piston snout with a wrench, slides the piston system 145 into the upper 1, releasing the piston snout from the gas block 130, and then slides the piston system 145 forward out of the upper gas tube hole 126, removing it. The user then slides the rear end 139 of the straight gas tube 136 with ferrule 137 into the upper gas tube hole 126, slides the front end 138 into the gas block gas tube hole 144, tightens the ferrule 137 with a wrench, inserts the bolt carrier 101 into the upper 1, and replaces the handguard.

Improved Anvil Connection

When using a gas piston system rather than a direct impingement system, the gas key 111 is replaced with an anvil 116. Much higher forces 110 act on the anvil 116 than on the gas key 111 during shooting, placing high shear forces on the two screws that anchor the anvil 116. An improved anvil connection adds new structural elements both to the anvil itself, and to the portion of the bolt carrier 101 that receives the anvil 116. The improved anvil, shown in FIGS. 53, 54, 55, 59, 60 and 61, has a similar footprint to the improved gas key 111, and sits in the same location on the bolt carrier 101, as shown in FIGS. 50, 51, and 53-57. The rear wall 107 is the most important change, as shown in FIGS. 50, 51, 54 and 55, which absorbs much of the gas forces 110 during shooting, relieving stress on the two screws. Additionally, a lug structure 119 is added to the bottom surface of the anvil 116, in front of the screw holes 118, as shown in FIGS. 59, 60 and 61. This lug 119 fits precisely into the gas hole 106 that is on the upper surface of the bolt carrier 101, and also absorbs the gas forces 110.

Expansion Chamber

To reduce recoil, an expansion chamber sleeve 141 is added to the barrel 70, as shown in FIGS. 73-77. A vent hole 133, see FIGS. 73, 74 and 76, is drilled into the barrel 70 between the gas block 130 and muzzle 75, and threading can be located on the outer surface of the barrel. A rear support collar is installed over the barrel between the two gas holes by some method such as a threaded collar, taper fit collar, or pinned collar. An expansion chamber sleeve 141 is mounted around the barrel 70, in between the gas block 130 and muzzle location 75, covering the vent hole 133, and held in place on the barrel by the rear support collar 131 and the muzzle support/expansion chamber adaptor 74. The ends of the system are sealed, not allowing any of the gas to vent until the bullet leaves the barrel.

With this expansion chamber setup, gas vents into an enclosed container 141, reducing overall pressure as the bullet exits the barrel, reducing recoil and muzzle rise. Another benefit of the expansion chamber sleeve 141 is that it puts the barrel 70 in tension, being connected with the rear support collar 142 and muzzle support/expansion chamber adaptor 74. This tension keeps the barrel 70 straighter.

In a preferred embodiment, the vent hole 133 is drilled into the top surface of the barrel 70. However, the vent hole can be located anywhere on the portion of the barrel that is enclosed by the expansion chamber. In FIGS. 73, 74, 75, 76 and 77, the rear support collar 142 is pictured as the flange of a gas block jam nut. However, the rear support collar can have a different structure and method of attaching at an appropriate location on the barrel, so long as it solidly holds the expansion chamber in place. For example, the rear support collar can be sized to hug the barrel at a location where the outer diameter of the barrel changes, such as the area labeled 73 in FIGS. 65 and 72.

Arca Handguard with Adjustable Weights

An improved handguard 150, preferred embodiment shown in FIGS. 78-81, includes pockets 156 (see FIG. 81) within an Arca rail 154 on the bottom side 154 of the handguard for configurable and removable weights 157. Weights are shown uninstalled in FIGS. 78, 79 and 81, and installed in the handguard in FIG. 80. A user can add or remove weights 157 for recoil mitigation or other purposes. Each weight 157 can be added at any pocket 156, for example with an Allen wrench to fasten bolts through bolt holes 158 in the weights 157 and bolt holes 155 in the pockets 156.

The weights and pockets shown in the Figures are rectangular, with two attachment holes in each weight. The weights and pockets can alternatively have a different shape, and each weight can have a different number of attachment holes, or an alternative method of attachment.

Handguard Lockup Mechanism

An improved handguard lockup mechanism, shown in FIGS. 82-85, replaces the traditional sloppy pinch bolt clamping system, instead holding the handguard 150 more securely in its concentric position around the barrel nut 84 and barrel 70, without movement and touching the barrel 70.

Locks 159 are integrated onto the curved surface of the handguard 150, at the breech end 151 and extending outwards in the muzzle direction. Each lock 159 has a claw hook 160, 161 on its breech end, shown in FIG. 85, which is configured to fit around the circumference and grab onto the breech side of the barrel nut 84. Each lock has a horizontal bolt hole 168. To install the handguard 150 onto the barrel nut 84, the user places the handguard 150 around the barrel 70, moving the handguard back to the barrel nut 84 and upper receiver 1. A bolt 162 and washer 163 are inserted into the front end of each of the three locks 159. As each bolt 162 tightens, the corresponding claw hook 160, 161 holds securely onto the barrel nut 84 as shown in FIG. 85, closing the gap between the upper 1 and handguard 150, thus creating an extremely solid hold and allowing the force to evenly distribute through the frontal face of the upper receiver and rear face 151 of the handguard.

To make the lock mechanisms easier to see, FIGS. 84 and 85 show the locks without showing the handguard, which would be connected to each lock. The handguard and locks are shown together in FIGS. 82 and 83.

In a preferred embodiment, two claw hooks 160 with the shape shown in FIGS. 87A and 87B are used for the top two locks, and a different claw hook 161 with the shape shown in FIGS. 86A and 86B is used at the bottom position. FIG. 88 shows a close-up view of a preferred embodiment washer 163 for use with each lock.

Some existing alternative handguard lock-up mechanisms require a proprietary non-standard upper receiver for the proprietary handguard to lock onto. The mechanism herein described can lock onto a standard barrel nut which can be used with any upper receiver or barrel.

Handguard Extender

To assist in very long distance shooting, an extension to a handguard shown in FIGS. 89-94 allows the shooter to rest the gun on a bipod which is located some distance in front of the muzzle 75. The handguard 178 has a generally tubular shape with multiple specifically shaped structures built into its outer surface, extending from near the breech end to near the muzzle end. A Picatinny rail 153 can be built onto the top surface of the handguard, as shown in FIG. 89. Two or more separate rails 165 (not Picatinny rails) extend along the length of the outer surface of the handguard, on the right side, left side and/or the bottom surface, as shown in FIGS. 90, 91 and 94. These rails have periodic holes 166 (for example, M-LOK holes as pictured) which are configured to receive stems of skid pads 167 made of high lubricity material. These skid pads 167 are installed on two or more of the outer surface of the right and left sides and the bottom 165, 166 of the handguard, as shown in cutaway areas in FIGS. 90 and 92, and make slidable contact with the inner surface of the handguard extender 174. The pads 167 also can improve the grip of a shooter's hand on the handguard.

A generally U-channel shaped handguard extender 170 has right and left sides 173 with inner grooves or slots 174, and a bottom 171 with inner grooves or slots 174, and is configured to slide from muzzle end backwards onto the high lubricity skid pads 167 on the two or more rails 165 of the handguard 178. FIG. 94 shows the inner grooves 174 and how the handguard extender 170 fits onto the handguard 178. The bottom surface 171 of the handguard extender has periodic holes 172 configured to receive a locking pin 177. The locking pin 177 allows the user to set the extender to the desired distance. When the handguard extender has been slipped rearwards into the user's desired location, a locking pin 177 can be inserted through one of the holes 172 in the handguard extender's bottom surface 171, and into a periodic hole in the bottom surface of the handguard, to lock the handguard extender 170 translationally in place.

When installed, the handguard extender extends forward. beyond and under the muzzle, leaving room for muzzle devices such as suppressors. The bottom surface 171 of the handguard extender can have an Arca rail shape, configured to receive attachment clamps. Long-range shooters will attach a bipod to the forward Arca rail or other structure, improving their aiming and accuracy. In a preferred embodiment, the skid pads 167 are made of high lubricity material with a coefficient of friction of 0.3 or less. In a preferred embodiment, the high lubricity material is Delrin. Other appropriate lubricious materials include polytetrafluoroethylene (PTFE), acetal, polyacetal, polyimide, polyether ether ketone (PEEK), polyphenylene sulfide (PPS), nylon and polyester.

The handguards shown in FIGS. 79, 80, 82, 83, and 89-93 have decorative cutouts 164 which also reduce the weight of the handguard. These cutouts are optional, and may have different shapes, sizes and arrangements than what is shown in the Figures. The exemplary handguard shown in FIGS. 90-93 and especially FIG. 94 has rails 165 on its right, left and bottom sides, to receive grooves 174 inside the handguard extender. The invention does not require all three rails, and one or two can be omitted if desired.

A handguard extender can be configured to fit onto a handguard with different dimensions from the one described above and shown in FIGS. 89-93. For example, by enlarging and widening the bottom portion of the handguard extender, it can be made to accommodate the handguard with weights shown in FIGS. 78-81.

Sloped Picatinny Rail

When aiming at a distant target, a user must allow for the ballistic curve of the bullet's trajectory, due to gravity. One way to do this is to adjust the sight elevation of the scope's elevation turret. For example, when a target is farther away, the scope is adjusted to look downwards, causing the user to tilt the barrel and muzzle upwards in order to see the target through the scope.

Each scope has a limited range of adjustment, so that if a target is too far away, the scope cannot be adjusted far enough downwards for the shooter to aim properly. An offset upper with downward sloped Picatinny rail 180 allows a shooter to use a scope to aim at more distant targets. A standard Picatinny rail is parallel to the barrel axis. The offset Picatinny rail has a slight angle 183, such that the rear end 181 is higher than the front end 182. In a preferred embodiment shown in FIGS. 95 and 96, the angle of inclination of the Picatinny rail 180 is 20 MOA, or ⅓ of a degree (too slight to be seen in FIGS. 95 and 96).

The descriptions of the various embodiments, implementations, variations, etc., have been presented for purposes of illustration, but are not intended to be exhaustive or limited to that disclosed. Modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. Aspects of the disclosure were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.