Abstract
A device comprised of bubble level inserted into and secured within a cavity located above the rifle grip and behind the barrel to facilitate the measurement and compensation of the rifle's cant while lining up the rifle's sights. The device is precision machined to allow the bubble to be aligned with the axis of the barrel to produce a true “zero-cant” condition. Graduation markings are placed on either left or right of the bubble level to allow the user to better judge the relative degree of cant. Methods of using the embedded cant indicator for precision shooting are presented.
Claims
1. A rifle comprising a stock section having a forward end and rear end, an action receiver section attached to the forward end of the stock section, a barrel having a centerline axis, and a cant measuring device comprising: a cavity positioned within the forward end of the rifle's stock section having a front wall, and left and right side walls, and a tubular bubble level embedded into the cavity and secured to the left and right sidewalls such that the outer surface of the level is below the outer surface of the stock section, and wherein the bubble is closely aligned with the centerline axis of the barrel when the rifle has zero degrees of cant. wherein the bubble moves perpendicular to the centerline axis of the barrel as the rifle is rotated about the barrel's centerline axis, and further wherein the bubble level can be viewed by the shooter when looking at the cavity.
2. The rifle of claim 1 wherein the cant measuring device further comprises a circular hole bored through one of the side walls of the cavity through which the bubble level is inserted into the cavity and the hole having a diameter equal to or larger than the diameter of the tubular bubble level's diameter.
3. The rifle of claim 2 wherein the cant measuring device further comprises a second tubular cavity bored into the other side wall and aligned with the center of the circular hole for receiving and securing one end of the tubular bubble level once inserted through the circular hole, and the tubular cavity having a diameter equal to or larger than the tubular bubble level's diameter.
4. The rifle of claim 3 wherein the cant measuring device further comprises a circular hole and second tubular cavity having a diameter closely approximate the diameter of the tubular bubble level so that when the bubble level is inserted into the cavity, the bubble level is prevented from moving independently from the rifle.
5. The rifle of claim 1 wherein the cant measuring device further comprises a centerline mark placed on the rifle's stock section in front of the bubble level and aligned with the centerline axis of the barrel.
6. The rifle of claim 5 wherein the cant measuring device further comprises a plurality of equally-spaced marks placed on either side of the center line mark to provide improved accuracy of measuring the rifle's cant from the position of the bubble inside the level relative to these marks as the rifle is rotated about the centerline axis of the barrel.
7. The rifle of claim 1 wherein the cant measuring device further comprises a centerline mark placed on the rifle's stock section behind the bubble level and aligned with the centerline axis of the barrel.
8. The rifle of claim 7 wherein the cant measuring device further comprises a plurality of equally-spaced marks placed on either side of the center line mark to provide improved accuracy of measuring the rifle's cant from the position of the bubble inside the level relative to these marks as the rifle is rotated about the centerline axis of the barrel.
9. A method of compensating for the cant of a rifle comprising: a) Identify a target through a rifle, the rifle comprising a stock section, an action receiver section, a barrel having a centerline axis, a sight reticle and a cant measuring device further comprising a cavity positioned within the rifle's stock section behind the action receiver section having a front wall, and left and right side walls, a tubular bubble level placed into the cavity such that the bubble is closely aligned with the centerline axis of the barrel when the rifle is vertically orientated and marking lines for observing the relative position of the bubble as the rifle is rotated about the barrel's centerline axis, b) Align the sight reticle with the target; c) Assess the degree of cant to the rifle by observing the left or right displacement of the bubble relative to bubble level's position marking lines; and d) Rotating the rifle about the axis of the barrel such that the bubble inside the level aligns with the centerline axis of the barrel.
10. The method of claim 9 further comprising the step of realigning the sight reticle cross-hairs relative to the target after removing the cant from the rifle.
11. A method of compensating for the cant of a rifle having a barrel, a stock section, and a bubble level embedded into the stock section, the center of the bubble level in line with the axis of the barrel, the method comprising: a) Identify a target and its proximate distance from the rifle; b) Align the rifle with the target; c) Assess the degree of cant to the rifle using the alignment of the bubble relative to the centerline axis of the barrel; and d) Rotate the rifle about the axis of the barrel such that the bubble in the level aligns with the centerline axis of the barrel.
12. A cant measuring device for a rifle a stock section having a forward end attached to an action receiver and barrel further comprising: a) a cavity bored within the forward end of the stock having a centerline that intersects the vertical plane of and is perpendicular to the centerline axis of the barrel; b) a topside of the stock having a view port created by removing material from the stock such that the cavity can be viewed when the rifle is held in a shooting position; c) a bubble level inserted into said cavity such that at zero cant, the bubble inside the bubble level is aligned with the barrel's centerline axis.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view of the invention apparatus located in its position relative to the stock of the rifle and overall weapon platform. The barrel of the rifle and the sighting means are not shown but it is understood to one skilled in the art where these components would be located on this rifle stock assembly;
[0015] FIG. 2 top side view of the invention showing the bubble and calibration marks;
[0016] FIG. 3 is a left side view of the invention showing the various compartments housing the bubble level and interfacing with the remained of the rifle components;
[0017] FIG. 4 is bottom view of the preferred embodiment of the invention indicating length and width dimensions;
DETAILED DESCRIPTION
[0018] FIG. 1 illustrates the preferred embodiment of the invention as an element of an overall weapon assembly. This weapon assembly is comprised of multiple parts that are bolted together to provide a functioning rifle. In its most basic form, this particular weapon platform is comprised of a central stock 1, the cant indicator 20, the butt of the rifle 4, a recoil absorbing pad 5. The barrel of the rifle would attach at point 2. If the shooter desired a scope, it would be attached to the central stock at 6. As the shooter holds the weapon and views at the target through the scope in a direction parallel to the axis of the rifle barrel, the cant indication would be obtained by glancing downward at a bubble contained within the cant indicator assembly 20. By using the calibration lines, as will be further described in later Figures, the position of the bubble to the left or right of the center line will indicate the extent with which the rifle is tilted about the axis of the barrel. A shooter can either rotate the weapon to eliminate the cant or make the appropriate adjustment to the point of aim at the target. As has been learned from competition shooting, extreme accuracy of hitting the target typically requires a precisely trained and practiced shooter and a custom-set rifle that is calibrated to the shooters particular method of holding and aiming the firearm. Cant compensation is critical to improving shot accuracy. The special relationship between the shooter and his weapon i.e., knowing where the projectile will travel when aimed this particular way on this particular gun is extremely important high-accuracy shooting. Modern ballistic software-based calculators also have a function that the shooter can input the cant offset and the appropriate aim corrections are computed and displayed. The present invention allows the same level of high-accuracy shooting because every cant indicator is precisely machined and attached to the particular stock design which employs the device. Therefore, a given shooter can pick up any weapon with the invention installed and the cant compensation will be precise and repeatable. Now, a trained shooter has multiple weapons each with a predictable response to cant compensation.
[0019] This eliminates the need for a shooter having only one rifle which they can use that is set up by a specialist for high-accuracy shooting. In addition, more shooters can be trained because more weapons would be available with high-accuracy cant compensation systems.
[0020] FIG. 2 illustrates a top view of the section of the rifle containing the precision-machined bubble-level system that comprises the invention. In the preferred embodiment of the invention, the device is machined out of a solid block of steel 20. Other materials can also be used depending on the level of cost and durability desired. The dashed lines 21 indicate a tubular cavity that is machined out of the block through from one side but does not extend completely through to the other side. This allows the bubble level tube to be inserted or removed from one side and when pushed in, is held in proper place by contacting the closed end of the cavity. This cavity length is also precisely machined so that the bubble level when inserted is correctly aligned to the gradient markings 29. The diameter of the cavity is machined with very close tolerances (0.001″ typically) to the diameter of the bubble-level inserted therein. The length and width of the cavity 21 are dictated by the diameter and length of the particular bubble-level incorporated into the weapon system. In one embodiment, the bubble level is 0.375″ in diameter and the length is 1.500.″ An oval-shaped viewport 22 is machined into the top face that allows the shooter to view the bubble level tube that is inserted into the cavity. A bubble-level comprised of a glass or plastic tube sealed on both ends and containing a phosphorous liquid or other fluorescent liquid, but not completely filled, such that a bubble exists within the sealed tube. In this Figure, gradient markings 29 are spaced apart evenly along both the top edge and bottom edge of the viewport 22. These markings provide a reference point for the shooter to judge the level of cant displayed by the movement of the bubble within the level either to the left or right of true center. The markings are evenly spaced but are primarily for consistent reference and do not represent any actual degree of rotation. Once the shooter practices the firing the weapon in a canted situation, the location of the bubble relative to the left or right count of the markings is sufficient for the shooter to be accurate in cant compensation in other shooting circumstances. The gradients can be converted to actual degree of cant rotation simply by field calibration. This may be desirable, for example, if the shooter is using a ballistics software program that requires degree of rifle cant an input value to the calculation.
[0021] FIG. 3 illustrates a side view of the current invention showing the various elements machined into the block of steel 20 or other solid material. Items 23 and 24 are drilled and tapped to receive an attachment means, such as machine screws, for attaching the invention to the section of the stock above the grip of the stock. In the preferred embodiment, these machine screws are ¼″ diameter×⅝″ length and tapped to standard machine threads. All external surfaces of the invention are machined to flat to ensure that the device attaches securely and aligned properly to the other elements of the weapon stock. When in properly place on the weapon stock, these two screws point upward and secure the device to the stock assembly. In the preferred embodiment items 26 and 27 are machined and tapped cavities to receive four attachment means. This attachment means secures and aligns the device from the rear end. In the preferred embodiment, these attachment means are 10/32″ machine bolts. The invention also includes a contact base 25 that extends down below the back end of the central stock. This left side of this extended surface provides a contact surface for attaching a folding hinge piece or any other accessory item bolting on to the back end of the central stock.
[0022] In reference to FIG. 4, the bottom view of the invention shows the two threaded holes 23 and 24. In addition to securing the invention to the central stock via these attachment means, two ovular sections 26 and 27 are machined out of the invention for receiving similarly-shaped raised sections that are part of the central stock where the invention is placed. This “tongue and groove” style connection means ensures that the invention is properly aligned and located relative to other components that make up the weapon assembly. This connection means also adds strength to the invention to handle the stresses of firing the rifle and the weight of the stock components that are bolted to the invention. In the preferred embodiment, the height and width of the invention is 1.75″ and 1.23″ respectively. However, it is understood that the dimensions of the invention are relative to the size of the bubble level device incorporated into the firearm.
[0023] Various other changes may be made to the apparatus in size, proportions, and material of construction without departing from the meaning, scope, or intent of the claims which follow.
