The present invention relates to firearms, and more particularly to a rifle with tapered interfaces that enables the barrel of a rifle to remained centered relative to the receiver bore during thermal expansion of the rifle's components.
Modern firearms are designed and manufactured to operate with multiple inter-operational components and often with modular construction. In one example, an AR-10 or AR-15 style sporting rifle 100 uses a modular construction with an upper receiver 102 and lower receiver 104, as shown in
Upper receiver 102 is characterized by bolt carrier assembly, forward assist, charging handle, and gas-operated reloader. Ejector 118 provides for exit of spent cartridges from upper receiver 102. Barrel assembly 120 with handguard 122 attaches to upper receiver 102. Lower receiver 104 is attached to upper receiver 102 by removable rear take-down pin 124 and forward pivot pin 126. Removing rear take-down pin 124 allows upper receiver 102 to hinge and rotate about forward pivot pin 126, see
Barrel assembly 120 is typically secured to upper receiver 102 with a single barrel nut. The barrel nut torques the barrel to upper receiver 102. Unfortunately, the single barrel nut does not ensure, and generally does not provide, proper alignment between the bore of the barrel and the bore of upper receiver 102. Any misalignment between the bore of the barrel and the bore of upper receiver 102 can cause wear on the bolt, catastrophic failure of the bolt, and un-torquing of the barrel extension due to vibration and heat expansion. Moreover, even when the barrel is properly secured to the upper receiver via the barrel nut and barrel extension, the ignition of ammunition inside the barrel chamber still can cause the length of the barrel to move, i.e., “whip,” due to harmonic vibration. The harmonic vibration decreases the reliability and accuracy of the barrel.
A standard barrel mounting system for the AR platform relies on flat torque shoulders to mount the barrel to the barrel extension, to fit the barrel extension to the upper receiver, and to secure the entire system onto the upper receiver via a singular barrel nut. These torque shoulders are typically not perfectly flat and exhibit high points and low points, even if only by a few thousandths of an inch. The effect of this is that upon installation, the barrel bore may not sit center with the upper receiver bore, and the barrel muzzle may lean away from the upper receiver axis. Any trauma to the barrel or handguard can then cause the barrel to further move away from center and alignment because of the lack of secure and even contact points. This degrades the rifle's accuracy. Moreover, the barrel, barrel extension, upper receiver, and barrel nut are all typically machined from different metals, each with their own thermal expansion rate. When the weapon is fired and its component materials heat up at different rates, the barrel deviations from center and alignment can be exacerbated. This further degrades the rifle's accuracy, particularly during prolonged shooting, and results in a need to frequently re-zero the weapon.
Manufacturers have attempted to solve this problem by a process known as shrink-fitting or thermal fitting, which is under-sizing the internal diameter of the upper receiver (i.e., machining it smaller) and over-sizing the outer diameter of the barrel extension (i.e., machining it larger) to the point where they will not fit together, and then using heat to force the installation. More specifically, the manufacturer will heat up (and consequently enlarge) the aluminum upper receiver, insert the steel or stainless-steel barrel extension, and then allow the upper receiver to cool and consequently contract around the barrel extension. The parts are then further secured by the barrel nut. The idea is that the thermal fit process is more rigid and secure than components torqued on flat shoulders, and the thermal fit process therefore makes the rifle more accurate both out of the box and over time.
The problem with the above approach is the same thermal forces that are used to shrink-fit or thermal fit the parts are present during the normal operation of the weapon. When the rifle is shot, the rifle heats up, and when the rifle heats up, the component parts will thermally expand, all at different rates, thereby negating the effect of the shrink-fit or thermal fit installation. Moreover, a shrink-fit or thermal fit process cannot guarantee bore centricity or axis alignment.
Therefore, a need exists for a new and improved rifle with tapered interfaces that enables the barrel of a rifle to remained centered relative to receiver bore during thermal expansion of the rifle's components. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the rifle with tapered interfaces according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of enabling the barrel of a rifle to remained centered relative to receiver bore during thermal expansion of the rifle's components.
The present invention provides an improved rifle with tapered interfaces, and overcomes the above-mentioned disadvantages and drawbacks of the prior art. As such, the general purpose of the present invention, which will be described subsequently in greater detail, is to provide an improved rifle with tapered interfaces that has all the advantages of the prior art mentioned above.
To attain this, the preferred embodiment of the present invention essentially comprises a receiver, a barrel extension connected to the receiver at a first interface, a barrel connected to the barrel extension at a second interface, a barrel nut element connected to the barrel extension at a third interface and to the barrel at a fourth interface, and at least two of the first, second, third, and fourth interfaces being tapered interfaces. The tapered interfaces may be stably tapered such that a wedging effect is generated. The barrel extension may have two tapered interfaces. The barrel extension may have a forward external tapered interface connecting to the barrel nut element and a forward internal tapered interface connecting to the barrel. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims attached.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.
The following describes one or more embodiments with reference to the figures, in which like numerals represent the same or similar elements. While the figures are described in terms of the best mode for achieving certain objectives, the description is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the disclosure.
Upper receiver 202 includes bolt carrier assembly, forward assist, charging handle, and gas-operated reloader. Ejector 218 provides for exit of spent cartridges from upper receiver 202. Barrel assembly 220 with handguard 222 attaches to upper receiver 202. Lower receiver 204 is attached to upper receiver 202 by removable rear take-down pin 224 and forward pivot pin 226. Removing rear take-down pin 224 allows upper receiver 202 to hinge and rotate about forward pivot pin 226, see
In
Barrel assembly 276, 278 is mounted to upper receiver 202 using a two-stage or double independent taper-lock barrel nut assembly, as will be described in
In accordance with the embodiment of
In
In
By nature of internal beveled or tapered shoulder 316 contacting beveled or tapered shoulder 268, barrel 230, and correspondingly bore 242, is centered and aligned with upper receiver 202. Secondary barrel nut 300 is tightened to 54-108 newton meters (nm). Once the barrel alignment is secure, primary barrel nut 280 is tightened to 54-108 nm to lock barrel assembly 276 to upper receiver 202. The proper alignment between upper receiver 202 and bore 242 of barrel 230 avoids wear on the bolt, catastrophic failure of the bolt, and un-torquing of the barrel extension due to vibration and heat expansion. The proper alignment between upper receiver 202 and bore 242 of barrel 230 reduces harmonic vibration, while increase dynamics, durability, and accuracy of sporting rifle 200.
Barrel assembly 278 can also be mated to upper receiver using the double barrel nut 280 and 300 assembly process, similar to
As shown in
The tapered interfaces are stably tapered such that a wedging effect is generated. The barrel extension 414 has a forward external tapered interface 428 connecting to the barrel nut element and a forward internal tapered interface 430 connecting to the barrel. The barrel extension also has tapered interface 432 connected to the receiver 412. The barrel has an additional tapered interface 434 that contacts the barrel nut element. One of the second interface 420 of the barrel and the additional tapered interface 434 of the barrel is tapered rearward and the other one is tapered forward in the current embodiment.
The barrel nut element 422 includes a rear barrel nut portion 436 and a forward barrel nut portion 438 adjustably connected to each other. The rear and forward barrel nut portions each include a tapered interface 440, 442. One of the tapered interfaces of the rear and forward barrel nut portions interfaces with the barrel extension 414, and the other one of the tapered interfaces of the rear and forward barrel nut portions interfaces with the barrel 418. Only limited torque can be applied to the barrel within the barrel extension to prevent stretching or other deformation that could adversely affect accuracy, making a tapered interface with a portion of the barrel nut element desirable. The forward barrel nut portion, which also serves as a heat sink, is made of copper in the current embodiment. Copper provides eight times better thermal conductivity from contact than aluminum at the tapered interface 426 and prevents the barrel from separating from the receiver from thermal cycles. The receiver and rear barrel nut portion are made of aluminum. The barrel and barrel extension are made of stainless steel. The rear and forward barrel nut portions are threadably engaged to each other by threaded portions 450, 452. The barrel extension has three tapered interfaces 428, 430, 432.
The tapered interfaces have the following preferred, minimum, and maximum angles. A flatter angle less than the minimum angle would provide inadequate wedging, while a steeper angle than the maximum angle would provide excessive wedging. Tapered interface 416 between the barrel extension 414 and the receiver 412: 20° minimum, 25° maximum. Tapered interface 420 between the barrel extension 414 and the barrel 418: 25° minimum, 30° maximum. Tapered interface 424 between the barrel extension and the rear barrel nut portion 436 of the barrel nut element 422: 15° minimum, 18° maximum. Tapered interface 426 between the barrel and the forward barrel nut portion 438 of the barrel nut element: 55° minimum, 65° maximum.
The rifle with tapered interfaces 400 also includes a handguard 444 encircling the barrel 418. The barrel defines a barrel bore 446 and a gas port 448 communicating between the barrel bore and the exterior 454 of the barrel. A gas tube 456 received within the handguard and connected to the receiver 412 communicates between the gas port and the receiver. The barrel and barrel extension 414 are threadably engaged to each other by threaded portions 458, 460. The rear barrel nut portion 436 and the receiver are threadably engaged to each other by threaded portions 462, 464. The threaded portion of the receiver defines a slot 466 that receives a tension pin 468 connected to the barrel extension to prevent rotation of the barrel extension within the receiver.
To assemble the rifle with tapered interfaces 400, first the threaded portion 460 of the barrel extension 414 is screwed onto the threaded portion 458 of the barrel 418 and torqued to 150 ft lb. Second, the head space between the forward facing surface 470 of the barrel extension lugway and the head of a gauge (not shown) in a chamber 472 defined by the barrel is checked. Third, lubricant anti-seize is applied to all tapered interfaces. Fourth, the barrel extension is inserted into a central bore 474 defined by the receiver 412. Fifth, the threaded portion 462 of the rear barrel nut portion 436 of the barrel nut element 422 is screwed onto the threaded portion 464 of the receiver and torqued to 50-55 ft lb. Sixth, the threaded portion 452 of the forward barrel nut portion 438 of the barrel nut element is screwed onto the threaded portion 450 of the rear barrel nut portion and torqued to 45-50 ft lb. The forward barrel nut portion is torqued to 10% less than the rear barrel nut portion to avoid rotating and applying excessive torque to the rear barrel nut portion during installation.
The rifle with tapered interfaces solves the problems associated with the shrink-fit and thermal fit processes by relying on tapered interfaces to mount and secure the barrel 418. Tapers are well-known across industries to be self-centering and excellent mechanical fasteners that guarantee concentricity. Tapers resist movement because tapers necessarily rely on 360° contact and necessarily lack the high/low points that are found on flat shoulders. The thermal expansion of tapered components tends to make the tapered contact tighter and more secure, even in the context of different materials and thermal expansion rates. Therefore, heating of the components of the rifle with tapered interfaces 400 during prolonged firing does not adversely affect accuracy.
In the context of the specification, the terms “rear” and “rearward,” and “front” and “forward,” have the following definitions: “rear” or “rearward” means in the direction away from the muzzle of the firearm while “front” or “forward” means it is in the direction towards the muzzle of the firearm.
While one or more embodiments of a rifle with tapered interfaces has been described in detail, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. While the embodiments disclose multiple tapered interfaces, it is believed that having any one (or combination) of tapered interfaces with these characteristics can provide benefits for certain applications. Furthermore, although four tapered interfaces have been disclosed, it should be appreciated that at least two tapered interfaces interconnecting at least three of the four of the receiver, barrel extension, barrel nut element, and barrel is sufficient to achieve increased accuracy relative to conventional shrink-fit and thermal fit processes. A conventional vertical shoulder engagement between the rear barrel nut portion and the barrel extension could be used if maximum accuracy is not required, although such engagement is not preferred because thermal changes would create geometry changes. A conventional vertical shoulder engagement between the forward barrel nut portion and the barrel could also be used if maximum accuracy is not required, although such engagement is not preferred because thermal changes would create geometry changes. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.
Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
The present application is a Continuation of U.S. application Ser. No. 17/662,994, filed May 11, 2022, which claims the benefit of U.S. Provisional Application No. 63/265,701, filed Dec. 20, 2021, which applications are incorporated herein by reference. The present application also claims the benefit of U.S. Provisional Application No. 63/436,895, filed Jan. 4, 2023, which application is incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
63265701 | Dec 2021 | US | |
63436895 | Jan 2023 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 17662994 | May 2022 | US |
Child | 18544736 | US |