Patent Application
20070175077
This invention relates to firearms, and more particularly to stocks for rifles.
Higher power rifle calibers generate a recoil force against the shooter's shoulder that is perceived as uncomfortable, painful, or even injurious by least some shooters. A rifle typically generates a sharp force transient in reaction to a shot being fired. The sharpness of this force, or the rapid impulse of the recoil, increases the perception of recoil.
Many approaches have been taken to reduce perceived recoil. Compressible materials have been used, either in the form of padding on the shooter's shoulder, or on a butt-pad or attachment for the rear of the rifle stock. However, compressible materials such as soft rubber tend to degrade over time from use, and are readily damaged by harsh conditions in the field.
One approach to reducing recoil is in the form of a rifle stock with a rear end portion that is axially sprung with respect to the front end that supports the rifle action. One such method is disclosed in U.S. Pat. No. 6,834,455 to Burigana, which discloses a stock having a diagonal pattern of slots. The pattern extends from the upper rear to the lower front of the stock. This essentially divides the stock into front and rear portions, which are connected only by a number of slim spring-like elements, without any rigid connection. While possibly suitable for some applications, the diagonal pattern creates an angled response to axial forces, generating unexpected vertical motion in recoil. Further, while recoil absorption may be achieved, the design severs structural integrity between the stock portions, reducing rigidity where it might be sired, such as at the upper edge of the stock where a firm cheek rest is desired. By suspending the entire rear portion, structural integrity is compromised when flexibility is needed only for a limited part of the butt stock where the shoulder contacts.
The present invention overcomes the limitations of the prior art by providing a rifle stock having an elongated body with a forward end and a butt end. The upper and lower edges of the stock are solid and continuous from front to rear. A slot generally parallel to the butt plate is formed adjacent to the butt plate to allow limited flexing in response to recoil. The stock may be formed as a hollow shell with opposed side walls, with slots to find in each sidewall. Several parallel slots may be defined in each sidewall. The slots may be occupied by elastomeric elements.
The stock has a forward portion 22, a pistol grip portion 24, and an elongated body 26 having an upper edge 30, a lower edge 32, and a butt end 34. A butt plate 36 is connected to the butt end 34. The butt plate is a plastic plate of moderate flexibility, with an elastomeric covering on its rear surface to provide some cushioning and slippage resistance. Just forward of the butt end 34, a plurality of slots 40 are defined in the side walls of the butt stock. The stock defines a major axis 38 that is perpendicular to the plane of the butt end 34, and approximately parallel to the barrel axis 16, except to the extent that the butt end is slightly offset from perpendicular to the barrel axis.
As shown in
To provide for some limited localized flexibility of the stock to reduce the perceived forces of recoil for a shooter, the sidewalls 46 of the stock are formed with the slots 40. The slots are gently curved arcs, arranged in an array on each side adjacent to the butt end 34. In each array, the slot 50 nearest the butt is longest, and the slots 52, 54 are progressively shorter toward the forward-most slot 56. The ends of the slots form a tapering wedge or triangle. The end of each slot is semi-circular to avoid excessive stress concentrations. In a molded stock, the fibers entrained in the plastic material will tend to align with the contours of the curves, further increasing strength. The arrays are the same on each side of the stock. The longest, rearmost slot 50 extends nearly the entire height of the stock, ending just short of the upper and lower edges so that the stock has structural integrity at the upper and lower edges.
The stock has a rear span portion 60 forming the rearmost portion of the sidewalls 46. The span on each side is defined at the rear by the rim of the butt end 34, and in a forward direction by the largest slot 50. Because the slot 50 is an arc with a concave-forward shape, the span 60 is tapered toward the middle or intermediate portion, wider at its ends than at its middle. This provides for added flexibility in the middle, where the convex forward portion of a shooter's shoulder contacts the stock. The further spans formed between the other slots add flexibility, without compromising axial rigidity along the upper and lower edges.
Each slot is occupied by an elastomeric insert 62 sized to closely fit within the slot. The inserts are formed of rubber or an alternative elastomeric material such as urethane. The inserts serve to dampen vibration and flexing of the spans, so that flexing occurs only in response to a sharp transient of recoil forces. In addition, the inserts further provide a gripping surface, and block the slots against incursion of dirt and debris.
In the preferred embodiment, the stock is about 12.687 inches long, and has a nominal wall thickness of 0.160 inches. The height at the butt end (which is the length of the butt along a vertical line from the rears of the upper and lower stock edges) is 5.0 inches. The slots 50-56 have respective lengths of 4.0, 3.125, 2.218, and 1.265 inch. The slots have widths of 0.250 inch, and the spans between the slots have a width of 0.3125 inch. The rear span 60 has a width of 0.3125 inch at the middle, and 0.60 inch at the ends. The first slot 50 has a length of 80% of the height of the stock at that location, providing significant flexibility without compromising the structure of the stock. The spans have typical aspect ratios of length-to-width in the range of 4 to 12.
While the above is discussed in terms of preferred and alternative embodiments, the invention is not intended to be so limited. For instance, the stock need not be formed as a shell, but may be a solid body such as formed of wood, or filled fiberglass. In such variants, the slots would extend entirely through the stock. In other alternative embodiments, the rubber inserts could be omitted, or could be replaced with alternate material having softer or stiffer properties. The slots are shown as arcs concave forward, but may be concave rearward, straight, or wavy lines, or any other elongated shape, as long as they generally extend from top to bottom, generally parallel to the butt plate, so that the middle portion of the butt plate is suspended while the upper and lower ends of the butt plate are solidly connected to the stock.
