U.S. patent application number 12/074668 was filed with the patent office on 2009-07-23 for reticle for telescopic gunsight and method for using.
Invention is credited to Thomas D. Smith, III.
Application Number | 20090183417 12/074668 |
Document ID | / |
Family ID | 22542426 |
Filed Date | 2009-07-23 |
United States Patent
Application |
20090183417 |
Kind Code |
A1 |
Smith, III; Thomas D. |
July 23, 2009 |
Reticle for telescopic gunsight and method for using
Abstract
A gunsight reticle defines a system of dimensioned indicia
spaced at specific separations to improve aiming accuracy of a gun.
The indicia may include perpendicularly intersecting center
vertical and center horizontal hairlines, and four (or more or
less) horizontal range-marker lines disposed at specific angular
separations below the horizontal hairline in bisected relationship
with the center vertical hairline. Spacing of the range marker
lines below the center horizontal hairline is proportional to
bullet drop at selected ranges, depending upon ballistic
characteristics of bullet used. Relative lengths of said
range-marker bars on each side of the central vertical crosshair
are proportional to a specific crosswind (say 10 mph) at target
range reflected by respective range marker. The method involves
employing this reticle to determine distance to target, and using
distance thus determined to ascertain a precise aiming point on the
reticle. These indicia also have other useful characteristics that
allow the shooter to easily mentally calculate corrections for
crosswind, moving targets and shooting at targets that are above or
below the shooter at a significant angle.
Inventors: |
Smith, III; Thomas D.;
(Oklahoma City, OK) |
Correspondence
Address: |
DUNLAP CODDING, P.C.
PO BOX 16370
OKLAHOMA CITY
OK
73113
US
|
Family ID: |
22542426 |
Appl. No.: |
12/074668 |
Filed: |
March 5, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10983824 |
Nov 8, 2004 |
7343707 |
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12074668 |
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10306505 |
Nov 27, 2002 |
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10983824 |
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10101819 |
Mar 19, 2002 |
6591537 |
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10306505 |
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09152320 |
Sep 14, 1998 |
6357158 |
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10101819 |
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Current U.S.
Class: |
42/122 |
Current CPC
Class: |
F41G 1/473 20130101;
G02B 23/14 20130101; F41G 1/38 20130101; G02B 27/32 20130101 |
Class at
Publication: |
42/122 |
International
Class: |
F41G 1/38 20060101
F41G001/38 |
Claims
1. A reticle for use in a telescopic gunsight, the reticle
comprising: a center vertical hairline and a center horizontal
hairline intersecting in an intersection point; a first
range-marker disposed below the center hairline and at a first
distance below the center horizontal hairline and intersecting the
center vertical hairline; a second range-marker disposed below the
first range-marker and at a second distance below the center
horizontal hairline and intersecting the center vertical hairline;
a third range-marker disposed below the second range-marker and at
a third distance below the center horizontal hairline and
intersecting the center vertical hairline; a fourth range-marker
disposed below the third range-marker and at a fourth distance
below the horizontal hairline and intersecting the center vertical
hairline; and wherein the various features of the reticle
correspond to inches of subtention at 100 yards, and the first
distance is about 2.0, the second distance is about 4.8, the third
distance is about 7.5 and the fourth distance is about 10.5.
2. The reticle in accordance with claim 1 wherein the first,
second, third and fourth range-markers are horizontal hairlines of
sequentially incremental length.
3. The reticle in accordance with claim 2 wherein the lengths of
the first, second, third and fourth range marker lines are about
4.12, 5.90, 8.32 and 9.72 inches, respectively.
4. The reticle in accordance with claim 1 wherein the intersection
of the center vertical and center horizontal hairlines constitutes
a center point which defines an approximate bullet impact point at
100 and 200 yards, and wherein the sites of intersection of the
first, second, third and fourth range-markers with the center
vertical hairline constitute first, second, third and fourth
alternative approximate bullet impact points, respectively, at
ranges of 300, 400, 500 and 600 yards, respectively.
5. The reticle in accordance with claim 4 wherein the approximate
bullet impact points in the preceding claim are operable for a
first gun type, and the intersection of the centervertical and
center horizontal hairlines constitutes a center point which
defines an approximate bullet impact point at 100 yards and the
sites of intersection of the first, second, third and fourth
range-markers with the center vertical hairline constitute first,
second, third and fourth alternative approximate bullet impact
points, respectively, at ranges of 200, 300, 400 and 500 yards,
respectively, for a second gun type different from the first gun
type.
6. The reticle in accordance with claim 1 wherein center vertical
hairline and the center horizontal line each include two radially
distal portions each forming a post having radially directed
innermost and outermost extremities.
7. The reticle in accordance with claim 6 wherein the distance
between the intersection point of the center vertical and center
horizontal hairlines and each of the innermost extremities of the
posts on the center horizontal hairline is about 25 inches.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a divisional application of U.S.
application Ser. No. 10/983,824, filed on Nov. 8, 2004, which is a
continuation of U.S. application Ser. No. 10/306,505 filed on Nov.
27, 2002, which is a continuation of U.S. application Ser. No.
10/101,819 filed on Mar. 19, 2002, now U.S. Pat. No. 6,591,537,
which is a continuation of U.S. application Ser. No. 09/152,320
filed on Sep. 14, 1998, now U.S. Pat. No. 6,357,158, all of which
are incorporated herein by reference.
INCORPORATION BY REFERENCE
[0002] The following documents are incorporated herein by
reference:
[0003] 1. MALE MAGAZINE, November 1967, Article page 11, "The Man
who Rehsed To Die";
[0004] 2. The Instruction manual previously entitled "The Perfect
Shot" and currently titled "The TDS -TRI-FACTOR Mental Ballistics
Calculator System," by Thomas D. Smith III;
[0005] 3. The Instruction manual entitled "Tactical Stress
Management," by Thomas D. Smith, III;
[0006] 4. The Instruction manual entitled "The TDS TFU-FACTOR Rifle
Scope System" by Thomas D. Smith, III; and
[0007] 5. The Instruction manual entitled "The ADINO Combat Rifle
Scope System" by Thomas D. Smith, III. adjusted by devices within
the scope attachment system (external adjustments). Method of
adjustment has no significant influence upon reticle design or
use.
[0008] By firing one or more shots and making compensatory
adjustments of the relative position of the reticle center point,
the shooting system, which is comprised of rifle, bullet type and
velocity, scope and shooter is "zeroed in" so that aiming position
of the reticle crossed hairlines or reticle center point coincides
with point of bullet impact on the target.
[0009] In certain scope sighting systems, the reticle has a series
of evenly-spaced secondary horizontal hairlines that intersect the
vertical hairline below the center horizontal hairline. In those
systems, the respective points of intersection of the secondary
hairlines with the vertical hairline are typically used to estimate
bullet impact points at distances progressively greater than that
at which the rifle was "zeroed in" with the main (center)
horizontal crosshair. However, in order to utilize these secondary
horizontal crosshairs with accurate and predictable results, the
shooter must know distance from gun to target with a significant
degree of precision.
[0010] Various types of range finder systems have been disclosed
for telescopic gunsights. For example, U.S. Pat. No. 1,190,121 to
Critchett discloses a reticle having a series of target-spanning
rulings disposed above a baseline, the rulings corresponding to
associated shooting distances. In use, the shooter ascertains which
ruling above the baseline makes the most closely embracing fit on
the target, thereby determining the shooting distance (target
range). A separate crosshair aiming point is included in the
reticle for use in association with each chosen ruling above the
baseline.
[0011] The principle of the Critchett target-spanning rulings is
that certain targets are of known, or at least estimable size. For
instance, it is a fairly accurate estimate that for mature deer or
antelope, the distance between the top of the back at the shoulders
and the bottom of the chest cavity is about 18 inches. The
target-spanning rulings are spaced apart such as to span a known
target size at a known range. This manner of distance measurement
is consistent with conventional trigonometric considerations
wherein the triangle defined by the height of the target and the
viewing angle through the telescope's optical system can be
considered a right triangle, which accordingly establishes the
length of the base line distance to the distal side of the
triangle, namely the distance to the target.
[0012] U.S. Pat. No. 3,392,450 to Herter et. al. discloses a
reticle having a series of target-spanning circles of different
diameters which correspond to associated shooting distances.
Employing the same basic distance-measuring concept as Critchett,
the shooter employs for aiming purposes, that crosshair which
corresponds to the selected circle.
[0013] U.S. Pat. No. 3,190,003 to O'Brien concerns a range-finding
reticle for a telescopic gunsight having single centered vertical
and horizontal hairlines. The portion of the vertical hairline
below the horizontal centerline is provided with widened bar
regions extending various lengths below the centerline. Each bar
subtends a target of known size. By finding which widened region
corresponds to the height of the target, the shooting distance is
estimated.
[0014] U.S. Pat. No. 3,431,652 to Leatherwood discloses a
telescopic gunsight wherein the distance to the target is
determined by movement of upper and lower horizontal hairlines
along a fixed vertical hairline in a manner so as to bracket the
target. Once bracketed, the intersection of the lower horizontal
hairline with the vertical hairline serves as the crosshair aiming
point. In this aiming process, the alignment of the scope changes
with respect to the gun barrel, whereby the allowance for distance
is achieved when the centered crosshair is sighted directly on the
target.
[0015] U.S. Pat. No. 3,492,733 to Leathenvood discloses a distance
measuring system for a variable power telescopic sight that is
pivotally moveable in a vertical plane with respect to the gun
barrel upon which it is mounted. Cams within the scope and
rotatable by external means achieve vertical movement of the scope
so that horizontal framing hairlines will fit the target. A
specialized cam must be installed into the scope for each
particular type of ammunition employed.
[0016] U.S. Pat. No. 3,948,587 to Rubbert concerns a variable power
telescopic sight having a reticule provided with a vertical
hairline, a center horizontal hairline and three horizontal framing
lines disposed below the center horizontal hairline. Aiming is
achieved by positioning either the center crosshair or lower
crosshairs on the target, as dictated by the observed fit of the
target within the framing lines.
[0017] U.S. Pat. No. 4,403,421 to Shepherd discloses a telescopic
gunsight having spaced apart primary and secondary reticles which
are moveable relative to each other. The secondary reticle is also
moveable vertically and horizontally within the plane of the
reticle. The moveable two reticle system facilitates adjustments
for windage and elevation. Distance to the target is ascertained by
framing indicia on the secondary reticle.
[0018] The telescopic sights disclosed in the aforementioned prior
art patents are often of limited usefulness insofar as they do not
address many of the several factors that need to be considered in
the accurate aiming of a rifle under field conditions. Such factors
include: [0019] a) distance to target [0020] b) drop of bullet
caused by force of gravity [0021] c) hold-over or hold-under aiming
points [0022] d) wind drift correction [0023] e) correction for
phenomenon associated with gyroscopic forces on a gyroscopically
stabilized bullet (sometimes referred to as) [0024] 1) Yaw of
Repose effects (vertical displacements) [0025] 2) Magnus effects
(horizontal displacements)
[0026] These latter result from the effect of cross-wind or
shooting either up-hill or down-hill.
[0027] Older reticle systems often require that the shooter look
away from the target in order to make compensating adjustments and
almost always require complicated mental or physical manipulations.
Some of these designs may render the scopes difficult or slow to
use, and some require moveable mounting on the rifle, a situation
which typically subjects the scope to inaccuracy after repeated use
or abuse in rugged field conditions. Moreover, correct use of any
of these systems always requires the shooter to manage
extraordinary mental work in what can already be a stressful
situation. It is proven that such additional stress is associated
with decreased performance potential.
SUMMARY OF THE INVENTION
[0028] The present invention is embodied in a reticle design
concept for a gunsight and "sticker" system. By firing shots to
perform a simple drop test, the shooter can know which sticker to
choose in order to automatically calibrate this reticle to measure
distance to any size target, to provide precise drop compensation
aiming points for specific measured ranges beyond the normal
point-blank (zero) range for any bullet, to automatically provide
precise aiming points compensating for cross-winds and up-hill or
downhill shooting conditions, and to provide an accurate lead point
aiming corrections for moving targets, thereby providing an
accurate and effective method for aiming the rifle, all with
relatively simple and fast mental work that does not require
extraordinary effort by the shooter or any knowledge of the
particular ballistic characteristics of load or gun to which this
system is applied.
[0029] It is critical to note that the TDS system combines three
critical factors: [0030] 1) specially designed reticle; [0031] 2)
specially designed stickers (durable visual keys intended to be
attached to the gun); [0032] 3) test firing to prove required
sticker for the system and use.
[0033] The telescopic sighting system incorporates an optical
system comprised of a forward objective lens element, a rear
eyepiece lens element and intervening erector lens element, the
elements being protectively confined within an elongated tubular
housing adapted to be affixed to a firearm, such as a hunting rifle
(but not restricted to such use and application--with proper
adjustments, this system can just as well be applied to the
sighting system on a bow, handgun, artillery piece, airplane or
other instrument). The improvement provided by the present
invention comprises addition into said optical system within said
housing of a transparent reticle having indicia which
simultaneously provides accurately both the function of distance
measuring, range-specific aiming as well as wind related and other
trajectory corrections. The reticle is positioned between the
objective lens element and the erector lens element. The indicia
incorporates orthogonally intersecting center vertical and
horizontal hairlines, and four (or more or less) horizontal
combination range-marker and wind bar lines, which are disposed
below the center horizontal hairline with very specific vertical
spacings and intersecting in a bisected relation the center
vertical hairline.
[0034] Note that other carrier systems and other specific designs
for any means of achieving the same aiming goals through the same
basic functionality, which is derived from recognition of the
parabolic nature of a projectile trajectory, are envisioned and are
specifically recognized and claimed as intellectually and
functionally similar and therefore also protected by this
application.
[0035] The specific and precise configuration and positioning of
the range marker and wind bar lines enables the shooter to mentally
compute the range to the target and allow for bullet drop, wind
drift, gyroscopic effects, up-hill or down-hill angle shots and
target lead. With modest practice, a typical shooter can learn to
accomplish these tasks within in a split-second. The specific ratio
of the spacings of these secondary indicia is critical to the
functionality of this system. The accuracy achieved by this reticle
promotes shooter confidence which in turn leads to shooter
proficiency. Similarly, the simplicity of the basic member of this
system, as described herein, leads to simplicity of precise
application.
[0036] This system can also include range marker bars that
intersect the vertical axis at a slight angle. The purpose of this
characteristic is to automatically correct for the elevation
component of wind drift. It is a recognized fact that crosswinds do
cause bullets to raise or drop relative to the trajectory that
would occur without a crosswind. This characteristic is not
described in the drawings but is a recognized potential feature
that can have significant value in specific applications, such as
airplane and artillery sights, but is not limited to such
applications.
[0037] The basic reason that this system works relates to the
following facts. First, all projectiles fired in the gravitational
field and atmosphere of the Earth travel in a parabolic trajectory.
Shape of the curve described by this trajectory depends upon angle
of fire (with respect to the horizontal), atmospheric conditions
and gravitational factors, projectile exit velocity and the
ballistic efficiency of the projectile (which is described as
ballistic coefficient, or BC, for bullets). It is a fact that to a
reasonable approximation, all such curves contain a section near
the beginning (within the typical useful range of any projectile
launching device) that is shaped very similar to a similar a like
section from any other trajectory curve. By applying an expansion
in the longitudinal direction and possibly a rotation about the
vertical and horizontal axis to the curve represented by the slower
projectile, to a first approximation (and close enough for
practical purposes), such sections of the two curves will follow
indistinguishable paths. Refer to FIG. 12.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a side elevation view of a telescopic sight
embodying the preferred type of the present invention mounted upon
a gun of the type commonly used for hunting, target shooting and
related practices.
[0039] FIG. 2 is a schematic illustration of the internal
components of a variable power telescopic sight of the type shown
in FIG. 1.
[0040] FIG. 3 is an enlarged view showing an aiming reticle
component of the sight of FIG. 1 as it appears to the user of the
sight.
[0041] FIGS. 4A, 4B and 4C illustrate the use of calibration grids
for learning the use of the scope of this invention.
[0042] FIG. 5 illustrates the use of the scope of this invention on
large targets.
[0043] FIGS. 6A and 6B illustrate the use of the scope of this
invention on a small target.
[0044] FIGS. 7-11 exemplify sighting images perceived by the
shooter in various shooting situations.
[0045] FIG. 12 illustrates the reticle depicted in the form of a
decal for taping upon the objective extremity of the scope or some
other handy location. The left-hand Grid Line column serves as a
reminder to denote the actual number of lines with which to divide
into the animal's or target's outline for height measurement. When
determining distance to target, the upper right column, Aiming
Point at level angle, denotes bullet impact point for a "6 Factor"
gun zeroed or sighted-in at 200 yards. Using the grid-line center
point, at 100 yards the bullet impact will be 1.84 inches (about 2
inches) high, and at 200 yards the impact point will be on target
(zeroed)--200 yards is a typical "zeroing" range for such a gun and
load. At 300 through 600 yards the lower indicia (crosshairs)
provide a precise aiming point at each respective stated distance
(progressively, 300, 400, 500 and 600 yards) to give the desired
impact point. The upper center column, Aiming Point Grid Line at 45
degree Angle, denotes the angle correction when shooting uphill or
downhill. For a "6 Factor" gun, simply move up the equivalent of
one crosshair (about 2'' of angle subtention) for a 45.degree.
angle shot.
[0046] FIG. 12 illustrates the fundamental reason that this system
works: Sections of significantly different trajectories forced into
relative correspondence through the simple expedient of rotation
and horizontal scaling.
[0047] FIG. 12 (Rotation and horizontal scaling yields similar
sections for all trajectory curves).
[0048] FIGS. 12-26 provide additional description of the present
invention.
DESCRIPTION OF PREFERRED EMBODIMENT
(for the Purposes of Clarification Only)
[0049] Referring to FIGS. 1-3, a telescopic sight 10, embodying
this invention is shown attached by a suitable mount 35 to a gun
12. The sight 10 is formed by a tubular housing 11 containing a
forwardly positioned objective lens element 13, a rearwardly
positioned ocular or eyepiece lens element 14, an intervening
erector lens element 15, and a reticle 16 disposed between the
objective lens element 13 and the erector lens element 15. In the
case of vari-focal or zoom scopes, a positionally adjustable
magnifying lens 17 is associated with the erector lens element 15.
The exterior of the housing 11 may be equipped with rotationally
moveable features 36 for adjusting focus, parallax, magnification
ratio, windage and elevation. Each of the various lens elements may
be single lenses or combinations of lenses, either aligned in
proximity or glued together or a combination of these
compositions.
[0050] The reticle 16 is a circular, planar or flat transparent
panel or disk mounted within the housing 11 in perpendicular
relationship to the optical axis or line-of-sight 18 through the
scope, and is positioned between the objective lens element 13 and
the erector lens element 15, typically at a site considered to be a
front focal plane of the optical system within the housing. The
reticle 16 contains fine etched lines or hairline indicia
comprising a center vertical hairline 19 and a center horizontal
hairline 20, which orthogonally or perpendicularly intersect at a
center point 26. The reticle further defines first, second, third
and fourth horizontal range and aiming marker hairlines 21, 22, 23
and 24 (or other designs as may be appropriate to specific
applications) respectively intersecting the vertical hairline below
the center point 26 and vertically spaced apart and of sequentially
increasing length. Each such range and aiming marker hairline 21,
22, 23, and 24 is bisected by the center vertical hairline 19, in
the present design in a horizontal manner but potentially in an
angled manner as necessary to account to the vertical component of
wind drift, etc.).
[0051] We must also note that it is feasible to present a virtual
reticle into the sighting system by other means, chiefly
electronically, and that the absence of a physical reticle in no
way alters the functionality of the present invention; therefore,
any means of generating aiming points that achieves the same goal
as that described herein is fundamentally identical in nature and
is also claimed.
[0052] Each combination of a gun and bullet or cartridge must be
initially sighted in at 200 yards, or other selected basic zero
range, which depends critically upon the ballistic characteristics
of the specific bullet (refer to FIG. 12). The center point 26 then
represents the basic sighted-in bullet impact point. The points of
intersection of said first, second, third and fourth range marker
lines 21, 22, 23, and 24 with said vertical hairline, designated
first, second, third and fourth alternative aiming points 30, 31,
32 and 33, respectively, represent sighted-in bullet impact points
at distances that are a function of bullet trajectory for the
specific load used. For example, for a bullet and gun determined to
be a "6 factor" system, as will be explained, the aiming points are
for distances of 300, 400, 500 and 600 yards, respectively.
[0053] A "6-factor" gun and bullet combination is a system that
produces a 6 inch drop from a "sight-in" impact zero point at 200
yards to the bullet impact point when the same combination of gun,
bullet and scope adjustment settings is fired at 300 yards, using
the center point 26 as the aiming point. Bullets of different
characteristics and velocity (different gun and bullet
combinations) will produce different "factors." Thus the aiming
points 30, 31, 32 and 33 will correspond to different distances or
ranges, which the shooter, knowing the characteristics of the
bullet, will take into consideration when aiming and firing.
[0054] The aiming points 30, 31, 32 and 33 are useful because the
trajectory curves of different bullets are similar, even though the
bullets travel different distances--some similar-length section of
each curve, whether closer to the gun or further from the gun, will
have a sufficiently similar shape to allow accurate use of this
system (refer to FIG. 12).
[0055] The radially outer or distal portions of the center vertical
hairline 19 and center horizontal hairline 20 are widened to form
relatively wider or heavy posts 25 whose radially directed
innermost extremities 28 are disposed on a circular locus about the
center point 26. However, this is not a design limitation of this
system, the main horizontal and vertical crosshairs can be of any
particular design, as might be necessary to provide the best
performance in any particular application and could even be
partially or fully absent as when only a central dot is used.
[0056] The various dimensions and spacings of the indicia on the
reticle 16 are conveniently expressed as inches of subtention or
angle at 100 yards, rather than the actual engraved dimensions on
the reticle lens itself. Accordingly, the width of each of the
posts 25 is 5.5 inches of subtention, and the width of the hairline
portions of the center vertical and center horizontal hairlines 19
and 20, respectively, is 0.6 inches of subtention. The distance
between the center point 26 and the innermost extremities 28 of the
posts 25, that is the length of the center vertical and horizontal
hairlines 19, 20, respectively, is 25 inches of subtention.
However, it must be noted that these specific dimensions and ratios
of dimensions are not the only possible useful designs. The
important issue is usefulness in the specific application.
[0057] The distances or width of the separation between the
horizontal hairline 20 to and the first, second, third and fourth
range lines 21, 22, 23, and 24 below the center point 26 are 2.0,
4.8, 7.5 and 10.5 inches of subtention, respectively--but other
designs are feasible for other applications. Typically four, marker
lines are typically of equal 0.3 inch width of subtention and are
typically straight and orthogonally or perpendicularly bisected by
the lower half or lower portion of the center vertical hairline 19;
however, other line thicknesses and non-orthogonal intersections
with the vertical line are feasible and may be preferable in some
applications. When four such lines are used, the lengths of the
first, second, third and fourth range marker lines are 4.12, 5.90,
8.32 and 9.72 inches of subtention, respectively; however, other
lengths are feasible and may be preferable in some
applications--the lengths specified above correspond to required
corrections for a 10 mile per hour true crosswind component, which
is a wind speed to which many experienced shooters can recognize
and relate.
[0058] The foregoing dimensions are empirically derived and are
critical to the accuracy and ease of use of this system in the
standard application (such as a hunting rifle)--these datum are
fundamental to the concept. However, one can also envision more
complex systems that might be used for other applications wherein
the extended range elevation aiming lines might be thinner, longer
and include enlarged "dots" at specific intervals to indicate
corrections for various true crosswind velocities such as 5, 10, 15
and 20 miles per hour, etc. Moreover, for other applications, this
basic concept could be extended to include designs having more than
four range marker bars. No such application and embodiment should
be considered to fall outside the basic tenants of this concept and
therefore, this application is not limited to the specific design
described herein; rather, this concept should be understood to
cover any application wherein the spacings and lengths of the range
lines incorporate the required characteristics so as to correspond
to the parabolic nature of a projectile trajectory at any specific
incremental (or other useful) range interval and wind condition.
The central point of this art is that it uniquely recognizes the
parabolic drop and crosswind deflections characteristics of real
projectiles.
[0059] As noted elsewhere, in the particular embodiment described
herein, the "factor" for a particular gun and bullet combination is
determined by sighting it in at 200 yards using the center point of
the reticle. Using the same 200 yard sight center point, a group of
shots is then fired at 300 yards and average drop (in inches) is
measured. This figure becomes the "factor" that is used to compute
vertical bullet drop, wind drift deflection, both horizontally and
vertically, and gravity correction for both uphill and downhill
angle correction for that particular gun and loading.
[0060] Bullet drop is progressively curvilinear (following a
parabolic curve), and is well predictable out to about 0.72 seconds
of free flight (450 yards for a .308 Winchester; 500 yards for a
30106; 600 yards for a 7 mm Remington Magnum; and 700 yards for a
301378; all when used with high energy maneuverability
bullets--traditionally known as bullets having a streamlined shape
and a relatively high ballistic coefficient). Bullet drop for a
6-factor gun and bullet combination for example, results in a
6-inch drop at 300 yards. This factor is tripled to predict
400-yard bullet drop. This 400-yard drop is doubled to predict 500
yard drop. For 600-yard drop, the 500 yard drop is doubled and ten
(inches) is subtracted from that result. This corresponds to a
formula used to determine the spacing of these indicia.
[0061] For instance, a 6-factor bullet (150 grain 7 mm. Remington
Magnum fired at 3,200 fps) computes thusly: [0062] a. 300 yard
drop: 6'' [0063] b. 400 yard drop: 3.times.6=18'' [0064] c. 500
yard drop: 18.times.2=36'' [0065] d. 600 yard drop:
36.times.2=72-10=62''
[0066] In other words, for a 6-factor gun and bullet that is zeroed
at 200 yards, the bullet drops 6''@300 yards, 18''@400 yards,
36''@500 yards, and 62''@600 yards. Other specific formula and
extensions to longer times of flight are feasible so long as those
describe useful characteristics of real projectiles.
[0067] A reticle embodying the present invention having the above
characteristics and dimensions, will produce sufficiently accurate
shots when using the respective reticle aiming points at the
determined distances. For gun and bullet combinations that have a
factor other than six, center impact distances corresponding to the
various aiming points must be calculated accordingly. See Table
I.
[0068] It is a useful fact that variable magnification scopes
(commonly referred to as variable power scopes) with the reticle
positioned in the first focal plane (in this design, adjusting the
power setting of the scope also adjusts the absolute apparent
spacing between the range indica) can be used to automatically
adjust the described reticle, as required to provide to correct
holdover for practically any "factor" gun and load by the simple
expedient of adjusting the power setting to the required value, so
as to generate the correct spacing of the indicia. In some
applications, it might be necessary to alter the basic zero range
and range increment but such correspondence will always be
feasible.
[0069] Use of a scope utilizing this invention for measuring target
distance may best be visualized by referring to the grid line
charts as shown in FIGS. 4A, 4B and 4C. Each grid line chart
consists of a series of numbered horizontal straight lines
sequentially spaced an inch apart (inch of subtention at 100 yards
or approximately one minute of angle) and assumed to be visibly
distinct in the scope at the indicated ranges. A target such as a
9-inch tall prairie dog is drawn to occupy the top nine lines of a
chart, as shown in FIG. 4A, and assumed to be placed at a range of
100 yards. The scope is then sighted onto said 100 yard target,
producing the view shown in FIG. 4B wherein the top of the prairie
dog is placed at the center point 26, and the bottom of the prairie
dog falls between the third and fourth range marker lines, namely
between 7.5 and 10.5 inches of subtention from the center point 26.
By interpolation, the bottom of the target, having an actual height
of 9 inches, is 9 inches of subtention from the center point 26. It
is accordingly ascertained that the 9-inch high prairie dog target
is located at a shooting range of 100 yards.
[0070] It should be noted that the target heights subtended by the
horizontal range marker lines increase in direct arithmetic
proportion to the distance of the target from the gun. Therefore,
at 200 yards, the first, second, third and fourth range marker
lines measure targets of 4, 10, 15 and 21 inch actual heights
(rounded), respectively. At 300 yards, the first, second, third and
fourth range marker lines measure targets of 6, 15, 22.5 and 31.5
inch actual heights (rounded) respectively. At 400 yards, the
first, second, third and fourth range marker lines measure targets
of 8, 20, 30 and 42 inch actual heights (rounded) respectively.
[0071] When the same 9-inch prairie dog target is viewed for
example at 300 yards, the view through the scope is as shown in
FIG. 4C, wherein the target appears much smaller because of the
distance at which it is located, and the range marker lines now
correspond to progressive actual heights of 6, 15, 22.5 and 31.5
inches respectively in descending order down said center vertical
hairline. Now, with the top of the head of the target at the center
point, the bottom of the target will be located between the first
and second range marker lines. This position corresponds to 3
inches actual height at 100 yards or 9 inches actual height at 300
yards. It follows, that knowing the actual height of the target,
one can easily determine target range. In other words, in order to
determine distance to target, target height is divided by inch
reading on reticle. In the example of FIG. 4C, the 9 inch target
would measure 3 inches on the reticle; accordingly, target range is
9/3=3(.times.100), or 300 yards.
[0072] Once the shooter has determined target range, and when the
shooter knows the factor of the gun and bullet being used, the
scope can be accurately aimed by centering the appropriate indicia
along the vertical hairline upon the desired location of bullet
impact. For example, with a "6-factor" gun and bullet combination,
and having ascertained that the target is located at 300 yards, and
knowing that the main reticle center point 26 is for a 200 yard
range, the next lower aiming point, consisting of the point of
intersection 30 of the vertical crosshair 19 with the first range
marker 21, corresponding to 300 yards, is, under ideal conditions
and with a stationary target, used as the aiming point for a direct
hit.
[0073] Use of this reticle with respect to a Rocky Mountain Elk
having an estimated 25 inch chest height is illustrated in FIG. 5.
It is seen that the 25 inch chest is spanned by about 5 inches of
subtention of reticle distance. Accordingly, the range is
25/5=5(.times.100), or 500 yards, and aiming point 32 is employed
for shooting, centered upon target, again this assumes a "6-factor"
gun and bullet combination, ideal conditions and a stationary
target.
[0074] Compensation must be made for bullet deflection due to wind
drift, To this end, the gun must be pointed into the wind. This is
accomplished by moving the reticle aiming point in the opposite
direction an appropriate amount. For this purpose, the applicable
"factor" becomes the 10 mph wind correction or drift, applied in a
linear manner. [0075] a. at 300 yards the drift is 6''; [0076] b.
at 400 yards the drift is 6+6=12''; [0077] c. at 500 yards the
drift is 12+6=18''; [0078] d. at 600 yards the drift is
18+6=24''.
[0079] For a 5 mph wind, the drift values would be one-half the 10
mph values, and a 20 mph wind would require twice the 10 mph values
and similarly for other true crosswind velocities.
[0080] The sight picture for shooting at a 9-inch high prairie dog
at 100 yards is illustrated in FIG. 6A. The sight picture for
shooting at a 9-inch high prairie dog at 600 yards with a 10 mph
left crosswind is illustrated in FIG. 6B. The view through the
scope when shooting at a target at 500 yards is illustrated in FIG.
7. FIGS. 8 and 9 illustrate adjusted aiming points to compensate
for 10 mph and 20 mph right-to-left crosswinds, respectively. For
this purpose, the ends of the range marker lines, having the above
lengths, constitute aiming points to compensate for 10 mph winds at
the respective ranges. Length of the range marker bars on each side
of the vertical centerline are one half the total length or 2.06,
2.95, 4.16 and 4.86 inches of subtention at 100 yards
respectively.
[0081] Compensation must also be made for the effect on the path of
the bullet of the spinning thereof. The rifleman's idiom designates
this as a "Magnus effect." It may also be referred to as "Yaw of
Repose." these are the vertical and horizontal elements of
deflection in a crosswind when considering a gyroscopically
spinning projectile or missile.
[0082] The formula for compensating for the potential worst case
effect of Magnus is to adjust 114th the total value by sliding that
point onto the target. In the illustration of FIG. 10, there is
shown the aiming point as an interpolated point left one equal wind
bar (10 mph) and 114 above the left tip of the third range marker
line. (Unusually low-drag high-speed bullets may react to Magnus
only a small percentage of the adjustment in FIG. 10; however,
hunting bullets do not fall into this category.) The rule is to
construct a "kill zone" on the target and then hold "worst and
best" Magnus movement so that the bullet is aimed with sufficient
accuracy to intersect the kill zone.
[0083] Computing simultaneous Magnus and Yaw of Repose values and
crosswind values: [0084] 1. With conventional (right-hand) twist
barrels, these effect make the bullet rise with a right-to-left
crosswind, drop with a left-to-right crosswind. [0085] 2. Add 1/4th
the horizontal value vertically to the final aiming point using the
reticle wind bar as a transparency overlay.
[0086] As noted previously, it is also possible to incorporate
automatic vertical-component crosswind correction into the range
markers by aligning those at a slight angle to the horizontal so
that the sighting correction for a crosswind automatically
incorporates the required correction for the vertical component of
wind drift. While not embodied in the accompanying sketches, this
method is claimed and recognized as a logical extension and
improvement on the basic concept of this reticle design. It is
recognized that this method would require separate scopes for guns
with reverse rifling twist directions and for guns used in the
southern hemisphere and might require special angles for guns used
at certain locations. However, for the vast majority of hunting gun
applications, one basic correction angle would suffice to provide
sufficient accuracy of correction as to achieve the required shot
placement accuracy.
[0087] When shooting uphill or downhill, bullet impact point will
be higher than when shooting level at the same total target
distance. In other words, when computing uphill or downhill gravity
values, it must be noted that angle shots require less hold-over,
that is the aiming point is moved upwardly on the reticle, because
of a lesser gravity pull although bullet drag remains the same. A
sight picture and aiming point for a "6-factor" gun and bullet at a
45.degree. up-hill shot at 500 yards slant range is illustrated in
FIG. 1. The appropriate sighting adjustment in such situation is to
move up one range marker line for a 45 degree angle, twice that or
two range marker lines for a 60 degree angle, and one half that or
up one-half the distance between appropriate range marker lines for
a 30 degree angle.
[0088] The formula or adjustment for a 60'' angle shot, for
example, is as follows: [0089] a. at 200 yards, raise the aiming
point an amount equal to 2/3rds of the factor, or 4''; [0090] b. at
300 yards, double the 200-yard value, or 8''; [0091] c. at 400
yards, double the 300-yard value, or 16''; [0092] d. at 500 yards;
double the 400-yard value, or 32''.
[0093] The reticle of the present invention performs with each gun
and bullet with the same precise degree of accuracy. The shooter is
thus provided a similar but unique reticle decal for each
combination. It must be stressed that the associated decals are an
integral part of this system and as such, the concept of
application specific decals is also part of this art.
[0094] While a single reticle constructed as described above may be
used for most gun and bullet combinations, specialized reticles may
be needed for certain particular gun and bullet or cartridge
combinations, scope magnifications and unusual applications.
Therefore, the ratios of indicia spacings and lengths are not
unique and other ratios of and lengths can have value for specific
applications, so long as these correspond to range-finding
functions, etc., as describing a parabolic trajectory, the design
will be an obvious derivative of this basic concept. This is a
parametric design issue and the critical factor of interest is that
specific ratios of spacings and lengths are required to produce
useful results.
[0095] It is further to be stressed that with this design the
shooter need not divert attention from the image in the scope for
first determining distance and other corrections and second for
finding the proper aiming point.
[0096] A telescopic gunsight utilizing this invention is
particularly well suited for shooting at moving targets. It is
generally known that a deer starts running at about 12.5 mph. The
distance between the reticle center point 26 and the innermost
extremities 28 of the posts 25 compensates for a target moving at
12.5 mph. Further adjustments can be readily made for targets
moving at other estimated speeds and angles, in direct proportion
to the 12.5 mph speed adjustment.
[0097] The final sight picture provided by the reticle embodying
the present invention, corrected for range, wind, external
ballistics, and target movement results in a straight line aim and
shot at the target in the same manner as a point blank range shot.
This enables the shooter to have much more confidence in the result
and therefore to more easily achieve accurate shot placement.
[0098] Using a reticle of the present invention, observing the
target conditions, and applying the foregoing simple mental
calculations, an aiming point on the reticle is selected and
centered on the desired target impact point. This can be done
quickly with less stress or doubt, when compared to other systems.
The shooter can then concentrate on firing the gun in a relaxed
mode with a minimum of movement or "jerk" of the gun and then "look
the bullet into" the target--this is otherwise called "follow
through" and has long been recognized as critical to
marksmanship.
[0099] While particular examples of the present invention have been
shown and described, it is apparent that changes and modifications
may be made therein without departing from the invention in its
broadest aspects. The aim of the appended claims, therefore is to
cover all such changes and modifications as fall within the true
spirit and scope of this invention.
[0100] A final point of significant value revolves around the
difference between first and second focal plane reticle placement
in a variable power scope. The former design provides for a means
of making any "factor" reticle design fit any "factor" application.
The disadvantage of this method is that it requires use of the
variable power scope only at one specific power setting for the
particular application. The disadvantage of the latter method is
that it requires use of a specific "factor" reticle. Each system
has advantages and this art covers any and all such
applications.
* * * * *