AR Platform Firearm

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.

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.

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.

show a modular brass deflector which can be changed and removed by a user.show the ejection sideof an upper receiver, with the buffer endon the left and breech endon the right. The modular brass deflectoris attached to the upper receiverallowing 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 holethrough the top of the brass deflector portionon the ejection sideof the upper receiver, as shown in. This holecan 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 deflectorcan be installed by the user on top of the upper's case deflector portion, as shown in, for example with a screw. The connecting portionincludes the back endof the modular brass deflector, has a bolt hole, and is shaped (see) to hug the shape of the top surfaceof the upper's brass deflectorat and near the bolt location. A deflecting portionincludes the front endof the modular brass deflector, and extends forward and above a rear portion of the ejection port, with its inner edgesecurely coupling along the outer surface of the upper, above the ejection port.

After firing, spent cases are extracted and ejected by the bolt carrier. Upon ejection, cases travel backwards, impact the brass deflector,and change trajectory. The standard trajectory, caused by the standard brass deflector portionof the upper receiver, located behind the ejection port, is not well controlled or in an ideal direction. The modular brass deflectorcan 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 surfaceand a top barrieras shown in. The physical shape is profiled to cause an ejection direction.

In a preferred embodiment, the threaded holein the upper receiver's brass deflector portionis drilled to accommodate a 12 inch 10-32 button head cap screw, which is used to attach the modular brass deflectorand modular brass catchdescribed below. The improved brass deflectorcan be made of the same material as the upper receiver, for example 7075 aluminum alloy, and is usually made to match the look of the upper. 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.

As an alternative to the modular brass deflector,show a modular brass catchwhich can be installed and removed by a user.show different close-up views of the modular brass catch.show the ejection sideof an upper receiver, with the buffer endon the left and the breech endon the right. The attachment method and location for the modular brass catchis the same as that for the modular brass deflector. The manufacturer creates a holethrough the top of the brass deflector portionof the upper receiver, 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 catchcan be installed by the user with a screwthrough the modular brass catch holein the connecting portion, as shown in. In a preferred embodiment, the holes,are created to accommodate a 12 inch 10-32 button head cap screw.

When attached as shown in, the adaptor portionof the modular brass catch surrounds the top and front edges of the ejection port. The modular brass catch's “roof” portionextends along and above the horizontal top edge of the ejection port, with the modular brass catch's inner/receiver edgesecurely coupling along the body of the upper receiver. At the front endof the roof portion, the modular brass catch adaptor structurebends downward to extend along and in front of the front edge of the ejection port, still securely coupling its inner/receiver edgealong the body of the upper receiver. The shape of the adaptor portion can vary, and is profiled to direct spent cartridges in a collection direction.

The entire modular brass catchfits below the Picatinny rail, and can be attached as shown inwith a clipat its front endto the Picatinny rail. The modular brass catch structure creates a barrier, with its undersurfacepreventing spent cartridges from flying backwards, upwards or forwards, instead directing them outwards and downwards.

In a preferred embodiment, the modular brass catch roof portionextends outwards from the upper receiverabout ¾ inch, and the roof portionis approximately 2.9 inches long. At the front edge of the ejection port, the “front wall” portionof the modular brass catch extends at a 90 degree angle downwards, its inner edgehugging the body of the upper receiver, to a point ahead of and slightly below the front edge of the ejection port.

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

show combined lower and upper receiversconnected at the pivot pin and open at the takedown location.show takedown,and pivot pinholes,on the lowerand upper receivers, with sleevesto receive the steel pivot and takedown pins. 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, pivot and takedown pinshave 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 grooveon one end. Shown in, the upper receiverhas one pivot pinholeand one takedown pinhole. Shown in, the lower receiverhas two pivot pinholesand two takedown pinholes. A gunsmith or manufacturer installs tubular sleevesof appropriate lengths to fit into each pivot,and takedown pinhole,. These sleeves, shown close-up in, 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, and an outer diameter to mate with the inner diameter of the improved pinholes, and a liphaving a shape and size to mate with the grooveof the improved pinholes, to allow for a precise tight press fit of each insert, as shown in.show the sleevesinstalled into the pinholes of the upperand lower receivers.

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. The resulting steel on steel connection is much more durable than standard aluminum on steel connection.