U.S. patent application number 14/601363 was filed with the patent office on 2016-07-21 for shotgun tube having gain twist rifling.
The applicant listed for this patent is Lawrence Wilson Smith. Invention is credited to Lawrence Wilson Smith.
Application Number | 20160209146 14/601363 |
Document ID | / |
Family ID | 56407594 |
Filed Date | 2016-07-21 |
United States Patent
Application |
20160209146 |
Kind Code |
A1 |
Smith; Lawrence Wilson |
July 21, 2016 |
Shotgun Tube Having Gain Twist Rifling
Abstract
This invention relates to a shotgun tube, either an
inserted/attached short section that replaces a conventional choice
device, or one that forms an integral section of the shotgun
barrel. It is designed to provide major advances in two performance
features of shotguns: (1) It provides an extremely uniform expanded
shot pattern at short ranges 10 to 20 feet and (2) it provides
rotational stabilization for both rifled slugs and sabot encased
sub-caliber projectiles that significantly improves accuracy at
longer ranges.
Inventors: |
Smith; Lawrence Wilson;
(Tijeras, NM) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Smith; Lawrence Wilson |
Tijeras |
NM |
US |
|
|
Family ID: |
56407594 |
Appl. No.: |
14/601363 |
Filed: |
January 21, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F41A 21/18 20130101;
F41A 21/40 20130101 |
International
Class: |
F41A 21/18 20060101
F41A021/18 |
Claims
1. A shotgun barrel comprising: a screw-in device that mates to
industry-standard threads for installation of standard chokes; said
screw-in device having a nominal rifled length of about 4 inches;
and said screw-in device having a slope of the rifling twist that
starts at the chamber end of the unit with a low angular twist,
typically near to zero degrees.
2. A shotgun barrel according to claim 1, wherein the slope of the
rifling twist increases continually toward the muzzle end of the
barrel.
3. A shotgun barrel according to claim 1, wherein the final rifling
slope at the muzzle end of the barrel can be made to be any desired
larger angle, of about 30 degrees.
4. A shotgun barrel according to claim 1, wherein the groove depth
of such gain twist rifling is about 0.010 inches.
5. A shotgun barrel according to claim 1, wherein the groove width
of such gain twist rifling is about 0.125 inches.
6. A shotgun barrel according to claim 1, wherein the land width of
such gain twist rifling is about 0.125 inches.
7. A shotgun barrel according to claim 1, wherein the device can be
secured to the muzzle end of a shotgun by soldering.
8. A shotgun barrel according to claim 1, wherein the device can be
secured to the muzzle end of a shotgun by clamping.
9. A shotgun barrel according to claim 1, Wherein the grooves and
lands of the gain twist rifling are designed to function properly
with shotgun shells having a plastic shot cup.
10. A shotgun barrel according to claim 1, wherein the grooves and
lands of the gain twist rifling are designed to stabilize and
improve long range accuracy of rifled slugs and saboted sub-caliber
slugs.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field of the Invention
[0002] This invention relates to a shotgun tube, either an
inserted/attached short section that replaces a conventional choke
device or one that forms an integral section of the shotgun barrel.
It is designed to provide major advances in two performance
features of shotguns: (1) It provides an extremely uniform expanded
shot pattern at short ranges 10 to 20 feet and (2) it provides
rotational stabilization for both rifled slugs and sabot encased
suo-caliber projectiles that significantly improves accuracy.
[0003] 2. Discussion of the Prior Art
[0004] There have been numerous patents that bear on the subject of
improving the performance of shotguns especially in
improvement/modification of spread pattern of the shot charge. Most
patents are directed to choke tubes that are short cylindrical
tubes with different internal diameters, or chokes, on the shotgun
muzzle region. Hence the generic designation of the "choke" of the
shotgun being "full" for large constrictions and "modified" and
"cylinder" etc., as the constriction is eased.
[0005] An early patent for a changeable choke device is U.S. Pat.
No. 2,098,617 issued to R. M. Cutts and titled "Spreader Tube". It
describes the famous "Cutts Compensator" set of variable chokes. It
is not a rifled type of choke.
[0006] U.S. Pat. No. 8,458,945, U.S. Pat. No. 8,276,305, and U.S.
Pat. No. 7,523,581, propose to use types of propellant gas bypass
devices to interrupt the shot column. Their efficacy has not been
otherwise documented.
[0007] U.S. Pat. No. 4,711,048 and U.S. Pat. No. 3,492,750 relate
to muzzle attachments that provide a very large short constriction
at the shotgun muzzle, which would impart a significant inward
component to the shot column as it exits the muzzle. This inward
velocity should then provide a spreading component and result is
larger shot spreading. Again, the efficacy of this approach has not
been documented.
[0008] U.S. Pat. No. 4,071,971 describes a method of rifling a
removable choke tube at a small fixed angle of about 4 degrees with
respect to the bore axis. This is proposed to provide a pattern at
distances relative to skeet shooting, about 30 yards or 90 feet.
The patent also applies to rifling of the final 4 inches or so of
the complete shotgun barrel.
[0009] U.S. Pat. No. 2,484,988 uses a very short, less than one
inch, angled rifled section at the muzzle end of one embodiment of
a set of devices for controlling the shot pattern of a shotgun.
Again, the rifling is of constant twist and is slanted at an
undefined small angle relative to the device bore.
[0010] Both patents that use rifling near the muzzle make no
mention of the shot charge being encased in a plastic shot cup.
Since all current shotgun shells use such a shot cup, our gain
twist rifling is designed to be effective in spreading the shot
pattern from shells that have a plastic shot cup.
[0011] None of the patents cited here claim to produce uniform,
expanded patterns of shot at short ranges (10-20 feet) and
stabilize slugs, to improve accuracy at longer ranges (75-100
yds.),
SUMMARY OF THE INVENTION
[0012] Twist is the descriptor that describes the rate at which the
rifling of the barrel of a weapon rotates along the barrel length,
it is conventionally described as the length along the barrel in
inches that causes a full rotation (360 degrees) of the projectile.
The "twist" is then, for example, "1 in 9 or 1/9" for such a
rifling twist that completes a complete 360 degree revolution in 9
inches of travel along the length of the barrel. Conventionally,
the twist remains constant along the barrel length for almost all
firearms.
[0013] "Gain-twist" describes the situation where the twist becomes
more sloped relative to the barrel bore as the distance along the
bore goes from breech to muzzle. That is, when the twist at the
chamber end is, for example, 1 in 12 and it changes smoothly to
become 1 in 9 at the muzzle. Alternatively the description could be
that the angular slope of the rifling at the chamber has a given
value and the slope at the muzzle has a larger value.
[0014] We have applied this concept to produce a shotgun tube that
has a rifling slope significantly less than one degree at the
chamber end of the tube. This value changes smoothly and
consistently to a value as large as 30 degrees or more at the
muzzle end of the tube. This already designed and fabricated
shotgun tube is a screw-in type and has an overall length of about
4 inches.
[0015] Test firing of a shotgun having one of these devices
confirms that short-range (10 feet) patterns that are very uniform
with diameters of 15 plus inches can readily be achieved.
Similarly, patterns of smaller and larger diameters have been
derived from variations in the tube fabrication with various exit
angles for the gain twist.
[0016] This device can be made in shotgun gages, 410/20/16/12/10
and to fit shotgun barrels that are threaded to accept industry
standard screw-in chokes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1A An illustration of the device with serrated end.
[0018] FIG. 1B An illustration of the device without serrated
end.
[0019] FIG. 1C An end view of device with serrations and radial
rifling.
[0020] FIG. 1D An end view of device with radial rifling and no
serrations.
[0021] FIG. 2 An illustration of "Gain Twist" rifling.
[0022] FIG. 3A An end view of rifling with flat grooves and
lands.
[0023] FIG. 3B An end view of rifling with radial grooves and sharp
pointed "lands".
DETAILED DESCRIPTION OF THE INVENTION
[0024] "Gain Twist" describes the situation where the twist becomes
more sloped relative to the barrel bore as the distance along the
bore goes from breech to muzzle. That is, when the twist at the
chamber end is, for example, 1 in 12 and it changes smoothly to
become 1 in 9 at the muzzle. Alternatively the description could be
that the angular slope of the rifling at the chamber end has a
given value and the slope at the muzzle has a larger value.
[0025] The gain twist rifling of this invention is shown in FIG. 2,
[200]. The slope of the rifling with respect to the tube bore axis
increases as the distance along the bore increases from the chamber
end [202] to the muzzle end [204]. The dotted line straight line
[208] illustrates the non-linear character of the gain twist
rifling. Such a variable is readily programmed into a computer
numerically controlled (CNC) lathe or milling machine, thus
simplifying the production of such a device.
[0026] This slope is programmed as a quadratic equation (an
algebraic function dependent on the square of the length along the
bore of the tube from the chamber end) of groove offset from the
starting point at the chamber end of the tube as the length along
the bore axis increases. Such a function provides a smooth and
repeatable increasing groove slope angle [206] along the bore
axis.
[0027] Other functionality of the gain twist rifling can readily be
used for this purpose.
[0028] FIG. 3a and FIG. 3b illustrate the type of rifling that is
used here. FIG. 3a [302] shows a section of tube with both lands
[304] and grooves [306], both of which have flat surfaces. In this
type of rifling there are 12 lands and 12 grooves around the tube
inner diameter. The number of lands and grooves can be as small as
2 or as large as 24. The depth of each groove is about 0.010 inches
deep. Generally the width of grooves and the width of lands are
equal, although this convention is not universal, and this
invention functions with unequal groove and land widths.
[0029] FIG. 3b [320] illustrates a second type of rifling that has
been demonstrated. In this case the grooves are cut in the form of
a circular configuration with a radius of approximately 0.125
inches and forms circular grooves [322] that are again about 0.010
inches deep. They are cut so that the lands [324] form a sharp edge
and have essentially zero width.
[0030] Tubes of both groove types formed with an exit groove angle
at the muzzle end [204] of 30 degrees has produced an extremely
uniform pattern of some 20 inches diameter incident on a paper
target at a distance of 20 feet when #4 shot, #6 shot or #4
buckshot was tested. Tests with 00 buckshot showed a hollow ring
pattern that is undoubtedly caused by the small number of pellets
in the shell (9 pellets). All tests were performed using shotgun
shells that have a plastic shot cup encasing the shot charge.
HOW TO USE THE INVENTION
[0031] Similar results would be obtained if this type of gain twist
rifling were to be fabricated as manufactured for shotgun barrels
directly rather than as a screw-in removable tube.
[0032] Tubes with 6 degree, 12 degree, 20 degree and 30 degree exit
rifling slope were fabricated and tested. This illustrates that
such a gain twist tube can be designed and fabricated to match any
dispersion pattern that is desired for specific uses, such as
optimized for skeet shooting from specific stations, etc.
[0033] A second benefit that is derived from the gain twist tube is
that shotgun slugs are better stabilized when fired, using the gain
twist tube. Both conventional rifled slugs and sabot mounted
sub-caliber projectiles demonstrated improved accuracy and grouping
characteristics as compared to either smooth bored shotguns or with
conventional slug filing rifled shotguns.
[0034] This invention is designed to be effective in close range
home defense. Military and police should find this device useful in
room clearing maneuvers and fast moving targets.
[0035] When serrations consisting of 8 slots approximately 0.300
inch deep.times.60 degrees included angle are cut across the muzzle
end of this device creates very sharp points, which are useful for
breeching doors, windows etc., and is a very effective hand to hand
combat weapon.
BEST MODE OF THE INVENTION
[0036] FIG. 1B represents the best mode of the invention
contemplated by the inventor for carrying out the invention.
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