Anti-rattle biasing devices for firearms

An anti-rattling biasing device for firearms includes a spring configured to exert a biasing force against an upper receiver and a lower receiver of the firearm. The biasing force urges the upper and lower receivers firmly into contact with the pins that couple the upper and lower receivers, inhibiting small back and forth movement between the upper and lower receivers and thereby reducing or eliminating rattling of the upper and lower receivers when assembled together.

BACKGROUND

Many firearms, such as M4 and AR15 rifles, are constructed of two major components groups in the form of an upper receiver group and a lower receiver group. The upper receiver group may include an upper receiver, and other components such as a barrel, a bolt carrier group, a charging handle, and a handguard mounted directly or indirectly on the upper receiver. The lower receiver group likewise may include a lower receiver, and other components such as a trigger assembly, a butt stock, a buffer, and a grip mounted directly or indirectly on the lower receiver.

The upper receiver typically is connected to the lower receiver by removable pins located on the forward and rearward ends of the upper and lower receivers. Due to normal manufacturing tolerances and normal wear from usage, the upper receiver can undergo a small amount of back and forth movement in relation to the lower receiver. Because the upper and lower receivers and their connecting pins are metal, this movement can manifest itself as rattling that can be heard and felt when the firearm is being handled. While such rattling has no effect on the functionality or safety of the firearm, it is often viewed by the user as a sign of poor quality in the firearm, and in some cases can affect a user's shooting accuracy.

Plastic inserts have been used to reduce rattling between upper and lower receivers. For example, plastic inserts may be placed between the takedown lug on the upper receiver and the adjacent surfaces of the lower receiver. These inserts, however, typically need to be trimmed to precisely conform to the gap between the takedown lug and the adjacent surfaces of the lower receiver, so that the insert firmly urges the upper and lower receivers into contact with their connecting pins. It can be difficult, however, to trim such inserts to the precise dimensions needed to achieve this desired effect, while still allowing the upper and lower receivers to be mated properly. Also the need to trim and install the insert adds extras steps and complexity to the assembly process for the firearm.

SUMMARY

The present disclosure relates generally to devices that exert a biasing force on an upper and lower receiver of a firearm to reduce or eliminate rattling of the upper and lower receivers.

In one aspect, the disclosed technology relates to a lower receiver group for a firearm, the lower receiver group including: a lower receiver configured to mate with an upper receiver of the firearm; and a biasing device mounted on the lower receiver, the biasing device including a spring configured to compress when the upper receiver is mated with lower receiver, and to exert opposing forces on the upper receiver and the lower receiver in response to the compression of the spring. In one embodiment, the biasing device positioned at least partly within a bore formed in the lower receiver. In another embodiment, the biasing device further includes a plunger, and the spring is positioned at least partly within the plunger. In another embodiment, the biasing device further includes a retaining pin configured to retain the plunger and the spring in the bore. In another embodiment, the plunger includes a substantially cylindrical first portion having a first diameter; a substantially cylindrical second portion having a second diameter greater than the first diameter; and a lip that connects the first and second portions.

In another embodiment, the bore includes a first portion configured to receive the first portion of the plunger and having a diameter approximately equal to the diameter of the first portion of the plunger; and a second portion configured to receive the second portion of the plunger and having a diameter approximately equal to the diameter of the second portion of the plunger; and the lower receiver includes a lip facing the second portion of the bore and configured to contact the lip of the plunger to limit movement of the plunger and the spring in a first direction. In another embodiment, the biasing device further includes a retaining pin configured to limit movement of the plunger and the spring in a second direction opposite the first direction. In another embodiment, the lower receiver defines a cavity configured to receive a takedown lug on the upper receiver when the upper and lower receivers are mated; the spring is configured to extend into the cavity when the upper and lower receivers are not mated; and the spring is further configured to be compressed by the takedown lug when the upper and lower receivers are mated.

In another embodiment, the biasing device further includes a plunger; the spring is positioned within the plunger; and the plunger is configured so that the takedown lug contacts the plunger when the upper and lower receivers are mated. In another embodiment, the plunger and the spring are positioned at least partly within a bore formed in the lower receiver, and the bore extends between the cavity and a lower surface of the lower receiver. In another embodiment, the lower receiver is configured to be coupled to the upper receiver by a first and a second pin; the opposing forces on the upper receiver and the lower receiver urge the first pin into contact with structure of the upper receiver and the lower receiver adjacent the first pin; and the opposing forces on the upper receiver and the lower receiver urge the second pin into contact with structure of the upper receiver and the lower receiver adjacent the second pin.

In another aspect, the disclosed technology relates to a firearm, including: an upper receiver group including an upper receiver; and a lower receiver group including: a lower receiver configured to mate with the upper receiver; and a biasing device including a spring configured to compress when the upper receiver is mated with lower receiver, and to exert opposing forces on the upper receiver and the lower receiver in response to the compression of the spring. In one embodiment, the biasing device is mounted on the lower receiver. In another embodiment, the biasing device is positioned at least partly within a bore formed in the lower receiver; the biasing device further includes a plunger; and the spring is positioned at least partly within the plunger.

In another embodiment, the plunger includes a substantially cylindrical first portion having a first diameter; a substantially cylindrical second portion having a second diameter; and a lip that connects the first and second portions; the bore includes a first portion configured to receive the first portion of the plunger and having a diameter approximately equal to the diameter of the first portion of the plunger; and a second portion configured to receive the second portion of the plunger and having a diameter approximately equal to the diameter of the second portion of the plunger; and the lower receiver includes a lip facing the second portion of the bore and configured to contact the lip of the plunger to limit movement of the plunger and the spring in a first direction.

In another embodiment, the biasing device further includes a retaining pin configured to limit movement of the plunger and the spring in a second direction opposite the first direction. In another embodiment, the upper receiver includes a takedown lug; the lower receiver defines a cavity configured to receive the takedown lug when the upper and lower receivers are mated; the spring is configured to extend into the cavity when the upper and lower receivers are not mated; and the spring is further configured to be compressed by the takedown lug when the upper and lower receivers are mated. In another embodiment, the biasing device further includes a plunger; the spring is positioned within the plunger; and the plunger is configured so that the takedown lug contacts the plunger when the upper and lower receivers are mated. In another embodiment, the biasing device is positioned at least partly within a bore formed in the lower receiver; and the bore extends between the cavity and a lower surface of the lower receiver.

In another embodiment, the firearm further includes a pivot pin configured to couple a forward end of the upper receiver to a forward end of the lower receiver; and a takedown pin configured to couple the takedown lug to the lower receiver, wherein: the opposing forces on the upper receiver and the lower receiver urge the pivot pin into contact with structure of the upper receiver and the lower receiver adjacent the pivot pin; and the opposing forces on the upper receiver and the lower receiver urge the takedown pin into contact with the takedown lug and structure of the receiver adjacent the takedown pin.

DETAILED DESCRIPTION

The following discussion omits or only briefly describes conventional features of firearms and firearm mechanisms that are apparent to those skilled in the art. It is noted that various embodiments are described in detail with reference to the drawings, in which like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are intended to be non-limiting and merely set forth some of the many possible embodiments for the appended claims. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be given their broadest reasonable interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless otherwise specified, and that the terms “includes” and/or “including,” when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. As used herein, the term “about” in reference to a numerical value means plus or minus 15 percent of the numerical value of the number with which it is being used.

Embodiments of the present disclosure relate generally to an anti-rattle biasing device for a firearm. Non-limiting embodiments of the device are described below with reference toFIGS. 1-11.

FIGS. 1-3, 6, and 8depict an upper receiver group20and a lower receiver group22of a firearm10. The firearm10is an M4/AR15-type rifle. The inventive concepts disclosed herein are described in connection with an M4/AR15-type rifle for illustrative purposes only; the inventive concepts can be applied to other types of firearms, including rifles, pistols, handguns, and the like.

The upper receiver group20includes an upper receiver26. The upper receiver group20also includes a charging handle28, an assist30, an ejection port cover31, and a handguard32mounted on the upper receiver26. Other components of the upper receiver group20, such as a barrel and a bolt carrier group, are not depicted in the figures, for clarity of illustration.

The lower receiver group22includes a lower receiver34, and a trigger assembly36mounted within the lower receiver34. The lower receiver group22also includes a pistol grip38, a buffer tube40, and a buttstock42mounted on the lower receiver34. Other components of the lower receiver group22, such as a buffer and a buffer spring, are not depicted in the figures, for clarity of illustration.

The upper and lower receivers26,34are coupled to each other at their respective forward and rearward ends. The forward ends of the upper and lower receivers26,34are coupled by a pivot pin44, shown inFIGS. 1-3, 6, and 8. The pivot pin44is disposed in through holes46formed in two flanges48located at the forward end of the lower receiver34. One of the flanges48is visible inFIG. 10. The pin44also is disposed in a through hole formed in a flange (not shown) located at the forward end of the upper receiver26.

The rearward ends of the upper and lower receivers26,34are coupled by a takedown pin47, shown inFIG. 1. The takedown pin47is disposed in through holes50formed in opposite sides of the lower receiver34; and in a through hole52formed in a takedown lug54that extends downward from the rearward end of the upper receiver26.

The upper receiver26is mated to the lower receiver34by positioning the flange on the forward end of the upper receiver26between the flanges48of the lower receiver34while the upper receiver26is tilted downward as shown inFIGS. 2 and 3; and aligning the through holes46in the flanges48with the through hole in the flange on forward end of the upper receiver26. The pivot pin44is inserted through the aligned through holes to couple the forward ends of the upper and lower receivers26,34.

The upper receiver26then is rotated about the pivot pin44to a substantially level orientation as shown inFIGS. 1 and 9, to align the through hole52in the takedown lug54with the through holes50in the lower receiver34; and the takedown pin47is inserted through the aligned through hole52and through holes50, to couple the rearward ends of upper and lower receivers26,34. As can be seen inFIG. 8, the takedown lug54is positioned within a cavity55formed in the lower receiver34once the upper and lower receivers26,34have been mated.

The lower receiver group22includes an anti-rattle biasing device60. The biasing device60is mounted on the lower receiver34, and is configured to exert an upward force on the upper receiver26. The upward force inhibits rattling and other low-displacement, back and forth movement of the upper receiver26in relation to the lower receiver34. Such movement otherwise can result from the manufacturing clearances that normally exist between the adjacent surfaces of the upper receiver26, lower receiver34, pivot pin44, and takedown pin47, and from normal wear of these components.

The biasing device60is positioned within a bore61formed in the lower receiver34. As can be seen for example inFIG. 4, the bore61extends between a lower surface62of the lower receiver34; and a bottom surface or floor63of the cavity55. The bore61is aligned with the takedown lug54when the upper receiver26is mated with the lower receiver34, as can be seen inFIG. 9.

Referring toFIGS. 4, 5, 7, 9, and 11, the biasing device60comprises a plunger64; a spring65, and a retaining pin66. The spring65is positioned within the plunger64. The plunger64has an open end and a closed end, with the open end facing downward from the perspective ofFIG. 11. The retaining pin66is positioned below the plunger64and the spring65, and prevents the plunger64and the spring65from backing out of the bore61in the downward direction.

The bore61has a first or upper portion68a, and a second or lower portion68b, as can be seen inFIG. 4. The upper and lower portions68a,68bare cylindrical. The outer diameter of the upper portion68ais less than that of the lower portion68b. As a result of the reduction in diameter between the upper and lower portions68a,68b, the lower receiver34defines a lip70located along the interface between the lower and upper portion68b,68a. The lip70faces downward, toward the lower portion68b, as shown inFIG. 4.

The plunger64is formed from a relatively strong and durable material such as stainless steel; the plunger64can be formed from other materials in the alternative. The plunger64has a substantially planar upper surface74; and a first or upper sidewall76that adjoins the upper surface74. The plunger72also includes a lip78, and a second or lower sidewall80. The lip78adjoins, and connects the upper sidewall76and the lower sidewall80.

The outer diameter of the upper sidewall76is selected so that the upper sidewall76fits within the upper portion68aof the bore61with minimal clearance. The outer diameter of the lower sidewall80is selected so that the lower sidewall80fits within the lower portion68bof the bore61with minimal clearance as can be seen, for example, inFIG. 7.

The plunger64is inserted into the bore61from the bottom of the bore61, from the perspective ofFIG. 11. The lip70on the lower receiver34acts as a stop on the upward movement of the plunger64. In particular, interference between the lip78of the plunger64and the lip70limits the upward movement of the plunger64to an upper position depicted, for example, inFIGS. 7 and 11.

The length, or vertical dimension of the upper portion of the upper sidewall76is selected so that a portion of the upper sidewall76protrudes from the upper end of the bore61and extends into the cavity55when the plunger64is in its upper position. In some embodiments, the upper sidewall76can extend into the cavity55by about ⅛ inch to about ½ inch, such as about ¼ inch, when the plunger64is in its upper position, i.e., the upper surface74of the plunger64can be located about ⅛ inch to about ½ inch, such as about ¼ inch, above the floor63of the cavity55when the plunger64is in its upper position. The extent to which the plunger64extends into the cavity55is application-dependent, and can vary with factors such as the desired amount of force the biasing device60is to exert on the upper receiver26, the dimensions of the upper and lower receivers26,34, the spring constant of the spring65, the manufacturing tolerances of the upper and lower receivers26,34, the pivot pin44, and the takedown lug54, and the like. The upper sidewall76can extend into the cavity55by more, or less than about 1/32 inch in alternative embodiments.

The upper sidewall76can have an outer diameter of about 5/32 inch to about 7/32 inch; and a height, or vertical dimension, of about 5/16 inch to about ⅜ inch. The lower sidewall80can have an outer diameter of about 7/32 inch to about 9/32 inch; and a height, or vertical dimension, of about 7/16 inch to about ½ inch. These dimensions are presented for illustrative purposes only; the upper and lower sidewalls76,80can have other dimensions in alternative embodiments.

The spring65is a helical coil spring. The spring65is a linear spring, i.e., the relationship between the displacement of the spring65and the force exerted by the spring65is linear. The spring65can be a non-linear spring in alternative embodiments. The spring65can have a spring constant of about 150 pounds per inch to about 250 pounds per inch, such as about 175 pounds per inch to about 225 pounds per inch. The optimum spring constant for the spring65is application-dependent, and can vary with factors such as the desired amount of force the biasing device60is to exert on the upper receiver26, the overall length of the spring65, the deflection of the spring65when the upper and lower receivers26,34are mated, and the like. The spring65can have a spring constant greater, or less than the above range in alternative embodiments.

The spring65has an outer diameter about equal to an inner diameter of the upper sidewall76of the plunger64, so that the spring65can fit within the upper sidewall76with minimal clearance. The spring65has an overall length, in its uncompressed state, that is greater than the height, or vertical dimension, the plunger64, so that the plunger64can move downward in the bore61before bottoming out on the retaining pin66. The overall uncompressed length of the spring65can be about ½ inch to about ⅝ inch. The optimum length of the spring65is application-dependent, and can vary with factors such as the desired amount of force the biasing device60is to exert on the upper receiver26, the spring constant of the spring65; the overall height of the plunger64, the deflection of the spring65when the upper and lower receivers26,34are mated, and the like. The spring65can have a length greater, or less than the above range in alternative embodiments.

As noted above, the retaining pin66is positioned below the plunger64and the spring65, and prevents the plunger64and the spring65from backing out of the bore61in the downward direction. The retaining pin66extends across the lower portion68bof the bore61. The ends of the retaining pin66are disposed in through holes82formed in opposite sides of the lower receiver34. One of the through holes82is visible inFIG. 4. The retaining pin66can be retained in the through holes82by a press fit or other suitable means.

The biasing device60can be installed on the lower receiver34by, for example, inverting the lower receiver34so that the lower, or wider end of the bore61faces upward. The plunger64then can be inserted into the bore61so that the upper sidewall76becomes disposed in the upper portion68aof the bore61and protrudes partially into the cavity55of the lower receiver34as discussed above; and the lower sidewall80becomes disposed in the lower portion68bof the bore61. As can be seen inFIGS. 7 and 11, interference between the lip78of the plunger64and the lip70on the lower receiver34limits the movement of the plunger64toward the upper, or narrower end of the bore61, so that the plunger64assumes its upper position within the bore61.

The spring65can be dropped into the inverted plunger64, so that an end of the spring65rests against the closed, i.e., upper, end of the plunger64. If necessary, the spring65can be compressed slightly using suitable tooling, so that the spring65clears the through holes82. The retaining pin66then can be inserted into the through holes82, to secure the spring65and the plunger64in the bore61, thereby completing installation of the biasing device60.

Once the biasing device60has been installed in the lower receiver34, the upper receiver26can be mated with the lower receiver34in the above-described manner. As noted above, the bore61aligns with the takedown lug54when the upper and lower receivers26,34are mated; and the uppermost portion of the plunger64protrudes from the bore61and into the cavity55when the upper and lower receivers26,34are in a less than fully mated state. Consequently, a lower surface84of the takedown lug54contacts the upper surface74of the plunger64as the upper receiver26is rotated about the pivot pin44during the final stage of its mating process with the lower receiver34, as depicted inFIG. 7.

Once the lower surface84of the takedown lug54contacts the upper surface74of the plunger64, continued rotation of the upper receiver26causes the takedown lug54to exert a downward force on the plunger64, and to move the plunger64downward, from the perspective ofFIG. 9. Because the spring65is restrained on its bottom end by the retaining pin66, the downward movement of the plunger64causes the spring65to compress as shown inFIG. 9.

The through hole52in the takedown lug54aligns with the through holes50in the lower receiver34when the upper receiver26has been rotated to its fully mated position. The takedown pin47is inserted into the aligned through holes50,52to secure the forward ends of the upper and lower receiver26,34.

At this point, the spring65has reached its maximum compression. The compressed spring65exerts an upward reactive force on the upper receiver26via the upper surface74of the plunger64and the contacting lower surface84of the takedown lug54. In addition, the spring65exerts a downward reactive force on the lower receiver34via the retaining pin66. These counteracting forces urge the surfaces of the upper and lower receivers26,34adjacent the pivot pin44and the takedown pin47firmly into contact with the respective pivot pin44and takedown pin47. This contact in turn inhibits small relative movement between the upper and lower receivers that otherwise could result in rattling.

This biasing device60generates the above-noted biasing force automatically, upon the mating of the upper and lower receivers26,34. Thus, once the biasing device60has been installed, the anti-rattle bias is achieved with no action required on the part of the user other than mating the upper and lower receivers26,34in the normal manner. Also, there is no need to reinstall the biasing device60when the upper and lower receivers26,34are de-mated and then re-mated. And the biasing device60does not require any trimming or adjustment, since the spring65can exert a sufficient biasing force over the ranges of clearances normally expected between the upper and lower receivers26,34and the pivot and takedown pins44,47.

A set screw can be used in lieu of the retaining pin66in alternative embodiments, to retain the spring65and the plunger64in the bore61. The set screw can be retained in the bore61by threads formed around the lower periphery of the bore61. In other alternative embodiments, the bore61can have a closed bottom, i.e., the bore61can stop short of the lower surface62of the lower receiver34; and the spring65and plunger64can rest on the structure that defines the bottom of the bore61. In such embodiments, the plunger64and the bore61are formed without the respective lip78and lip70, so that the plunger64can be inserted into the bore61from a position above the bore61. In other alternative embodiments, a spring plunger can be used in lieu of the spring65, the plunger64, and the retaining pin66. In such embodiments, the bore61can have a constant diameter, and can have threads formed around the periphery thereof to engage the threaded body of the spring plunger. In other alternative embodiments, the biasing device60, and variants thereof, can be installed on the upper receiver26.