Compact Bolt Carrier Group

Firearms design continues to advance towards smaller and lighter configurations. One critical factor influencing the size and weight of firearms is the placement of the operating system relative to the bolt. Whether employing direct impingement, short stroke, long stroke, or internal piston mechanisms, the operating system frequently incorporates components situated above the bolt carrier. In numerous firearms, the operating system is situated above the cam pin. By lowering the cam pin and cam guide rail, it becomes possible to position the operating system closer to the bolt. A more compact bolt carrier group, crucial for diminishing the overall dimensions and weight of contemporary firearm designs, is required.

Another crucial factor affecting the overall size and weight of a firearm is the width of the bolt carrier group. Traditional firearm designs have been slow to depart from standardized bolt carrier sizes and shapes, which has stagnated innovation. Since the advent of the M4, firearms have often become larger and heavier than their predecessors. However, strategically positioning and shaping elements and components can enable the entire weapon system to become more compact and lightweight.

Further, firearm designs are continuously addressing concerns regarding part wear. One common strategy to mitigate wear is by incorporating steel components into the cam pin bearing surface and guide rails for the bolt carrier, thus reducing wear on aluminum receivers. However, the placement of these additional components has proven problematic in some designs. Many firearms feature stacked components, which increases both the height and weight of the weapon system. A more efficient design is necessary to reduce weight and complexity while preserving the advantages of minimizing wear.

This summary aims to introduce a simplified version of the concepts that are further explained in the Detailed Description. The following text is not intended to identify any key or essential features of the claimed subject matter, nor is the summary designed to determine the scope of the claimed subject matter.

The present invention is a compact bolt carrier group featuring a compact cam pin and cam guide rail. This design allows the operating system components to be positioned closer to the bolt than what is achievable with existing bolt carrier groups. Moreover, this configuration, coupled with the utilization of steel guide rails, facilitates the creation of a thinner bolt carrier with enhanced wear resistance compared to earlier firearm models. As a result, this combination of factors facilitates the creation of a firearm with a shorter and lighter overall design.

A few of the preferred embodiments are presented with illustrations and descriptions. Understandably, many modifications could be made without escaping the scope of the invention. Skilled professionals will appreciate the many inventive concepts that qualify as equivalents under the claims. The embodiments described below do not limit the spirit of the invention or the claims.

Not every figure contains every reference number. Terms such as “forward,” “rearward,” “upper,” “lower,” “bottom,” “top,” and “side” are used to refer to the orientations of the invention, as shown in the images. One skilled in the art will be able to determine how these orientational terms may change during the use of the invention.

The embodiments do not encompass all the essential components required for a fully functional firearm. Instead, only the parts necessary in the bolt carrier group are included to showcase the novelty of the invention. Common components vital to the operation of the bolt carrier group, such as the firing pin and a compatible receiver, are omitted from the drawings. It is expected that skilled professionals in the field will recognize how these components interact with the embodiments.

Four embodiments of the claimed invention are included in the drawings, not to limit the invention's scope but to show how elements and features may be positioned to achieve the same goal of this invention. Four embodiments of a compact bolt carrier group are identified as,,, and. The embodiments share many characteristics with each other. To highlight these similarities, these features will be given the same identification number.

displays an embodiment of a compact bolt carrier group, comprising a bolt carrier, rotating bolt, cam pin, cam rail slot, cam guide rail, cam path, and cam bearing surface. The cam pinextends out the cam pathin the upper section of the bolt carrier. The rotating boltand cam pinare in the locked position within the cam pathof the bolt carrier. The locked position is also considered the forward or firing position of the bolt carrier group when assembled in a complete firearm. The cam bearing surfaceand the cam rail slotare aligned so that the cam guide railcan pass through the cam rail slotand interact with the cam bearing surfacewhen the rotating boltand cam pinmove into the unlocked position within the cam pathof the bolt carrier. The cam pintravels from the front of the cam path, the unlocked position, the rear of the cam path, the locked position. Failure for the cam pinto complete its travel in the cam pathwill cause a failure in the operation of the firearm. The cam pinmust complete its travel in the cam path to successfully lock and unlock into the barrel extension. When successfully unlocked the bolt carrier group may move rearward and forward within the firearm receiver during use. When successfully locked the firearm may be fired during use. The cam guide railprevents premature travel of the cam pinfrom the unlocked to the locked position in the cam pathby means of physical interference. Additionally, the cam guide rail, in this embodiment, are a pair of rails that act as guide rials for the bolt carrierduring travel.

displays an embodiment of a compact bolt carrier groupin the unlocked position. The rotating boltand cam pinare in the unlocked position within the cam pathof the bolt carrier. The unlocked position is also considered the rearward or open position of the bolt carrier group when assembled in a complete firearm. In the unlocked position, the cam bearing surfaceis in contact with the cam guide rail, preventing the rotating boltand the cam pinfrom moving into the locked position until the bolt carrierhas completed its travel rearward and has returned to its forward locked position in the barrel extension.

The cam guide railserves a dual purpose. Firstly, it prevents premature rotation of the cam pinand rotating bolt. Secondly, it provides a rail for the bolt carrierto travel on, both to the rear of its movement and back into its locking position. Guide rails and cam rails are common elements in firearm design. The novelty of this invention is how low they these elements are positioned in the bolt carrier group; wherein the cam pinextends out the top portion of the bolt carrier. The low positioning, along with the dual function of a single rail for managing cam pin rotation and bolt carrier guidance, represents an incredibly efficient use of space and materials. While the embodiment presents the rails as inserts, it's important to note that this was done purely for demonstrative purposes to underscore the innovative nature of the invention. The design allows for considerable flexibility; the rails could be seamlessly integrated with the receiver, crafted from diverse materials, or even inverted, altering the typical male and female configurations. Furthermore, the arrangement of these rails can vary, whether as a single rail or multiple, and their distribution may not adhere to uniformity.

is an exploded view of an embodiment of a compact bolt carrier group. In this embodiment, the rotating boltfits in a circular recess in the front of the bolt carrier. The cam pinfits in a circular recess in the rotating boltso that rotational force applied to the cam pinwill translate to rotation of the rotating boltwhen assembled. When assembled, the cam pinprevents the rotating boltfrom falling out of the bolt carrier. This is insured by the travel limits of the cam path. In this embodiment, the rotating boltdesign resembles a shortened M4 multi-lug rotating bolt. Other embodiments featuring different rotating bolt designs, such as those with larger or smaller dimensions, differing numbers of lugs, or alternative configurations, are also encompassed within the scope of the claims, provided they utilize a cam pin extending through the upper portion of a bolt carrier.

is a prospective view of an embodiment of a cam pin. The cam pincomprised of a cam shaft, cam firing pin aperture, and cam bearing surface. The cam shaftinteracts with the cam pathand allows the cam pinto move forward or rearward on the cam path. The cam firing pin apertureallows for a firing pin to fit through the passage and act as the pivot point for the cam pinsrotation. The cam bearing surfaceis aligned with the cam rail slotand interacts with the cam guide railto prevent premature rotation while the bolt carrier groupis in the rearward position. The cam bearing surfacesits inside the shaft profile when viewed from the front elevation. While this cam pin profile has been utilized in various bolt carrier groups where the cam extends primarily from the side of the carrier, its application to bolt carrier groups with the cam extending primarily from the top is novel. This implementation represents a novel approach to bolt carrier group design, resulting in a more compact design for the entire bolt carrier group.

is a front elevation of a of an embodiment of a compact bolt carrier group with a dotted linemeasuring the vertical distance from the center of the firing pin aperture to the bottom of the cam bearing surface. In this embodiment of compact bolt carrier group, the distance from the center of the firing pin aperture to the cam pin and cam guide rail is 0.4 inches. Other embodiments of the claimed invention may include distances that are greater than or less than or equal to 0.4 inches.

is a prior art front elevation view of an embodiment of a prior art m4 bolt carrier groupwith a dotted linemeasuring the vertical distance from the center of the firing pin aperture to the bottom of the cam bearing surface. The approximate dimension from the firing pin aperture to the cam bearing surface is 0.5 inches. Notice the significant reduction in height of the cam pin compared to the prior art. Additionally, the head of the cam pin is noticeably smaller. In the previous design, the cam pin's head protrudes beyond the shaft body and is taller to accommodate the higher cam guide rail. In contrast, the cam pin in this embodiment is shorter than its predecessor. Furthermore, the bearing surface on the cam pin is situated within the profile of the shaft. This results in smaller and lighter components, reducing the total space required for rotation. Moreover, employing guide rails to stabilize the bolt carrier, particularly when situated low and closer to its center, enables a thinner profile while enhancing wear resistance.

andare a prospective view of an embodiment of a compact bolt carrier groupwith the rotating boltin the locked position and unlocked position respectfully. In this embodiment the bolt carrier groupfeatures a recoil springaround a operating rod. The operating rodcouples to the bolt carrier. In this embodiment, the cam guide railincludes an aperture at the forward end that allows for the operating rodto pass through to connect to the bolt carrier, but is not large enough for the recoil springto pass through, allowing forward force to be applied to the bolt carrier. In this embodiment the cam guide railis one piece. The embodiment includes a bufferattached to the rear end of the cam guide railto prevent damage from over travel of the bolt carrierduring operation.

andare a prospective view of an embodiment of a compact bolt carrier groupwith the rotating boltin the locked position and unlocked position respectfully. In this embodiment the bolt carrier groupfeatures two recoil springsaround two operating rods. The operating rodspass through apertures in the bolt carrier. The apertures are not large enough to allow the recoil springsto pass through, allowing forward force to be applied to the bolt carrier.

andare a prospective view of an embodiment of a compact bolt carrier groupand barrel extensionwith the rotating boltin the locked position and unlocked position respectfully. In this embodiment the bolt carrier bodyextends forward. A operating rodpasses through an aperture at the front of the bolt carrier. The aperture is not large enough for the recoil springaround the operating rodto pass through, allowing forward force to be applied to the bolt carrier. The embodiment includes a bufferto prevent damage from over travel of the bolt carrierduring operation. The embodiment also includes a charging handlefor the user to charge the bolt carrier group during operation.

These embodiments are intended to showcase, without limiting, the numerous configurations possible for a novel compact bolt carrier group. Those with expertise in the field can appreciate the range of potential combinations of springs and operating rods that could be utilized without departing from the essence of the claims. While short stroke configurations are highlighted, variations such as internal piston, long stroke, and others can also be incorporated into the design of a compact bolt carrier group within the scope of the claims.