What makes bullet spin

The location and dimensions of the vane surfaces may be selected to balance the torque on the bullet to avoid wobble. The bullet may have a single vane surface, for example indented in an otherwise planar base end, which forms a plane perpendicular to the flight axis The tip 16 may have a suitable shape such as a closed circular end, a cone, a bicone, an ogive, or others.

The base 14 may have the shape of a stepped cam disc. The vane surfaces may be arranged in a ring form about the axis In some cases the base 14 does not extend laterally beyond a maximum lateral width of the cylindrical body A smoothbore barrel may lack rifling grooves along a portion or the entirety of the axial length of a bullet travel portion of the interior cylindrical surface of the barrel.

A smoothbore barrel 19 may have a continuous interior diameter along the axial length of the barrel, although in some cases the barrel 19 may taper or otherwise change in diameter along a part or all of the axial length. A barrel with helical grooves or polygonal rifling imparts a stabilizing gyroscopic spin to a projectile that prevents tumbling in flight and improves accuracy. Thus, rifled barrels are used in preference over smoothbore barrels.

However, the shaped base 14 of the bullet 10 disclosed here imparts a torque that causes the bullet 10 to spin in a rotational direction 42 as it passes through even a smoothbore barrel Thus, bullet 10 may still achieve spin, and hence improved flight stability and accuracy, despite the lack of rifling in the barrel. A smoothbore barrel 19 may improve the efficiency of force transfer to the bullet from compression of gas pressure behind bullet 10, by sizing the bullet diameter 56 and bore diameter 54 of the barrel 19 to correspond to one another, in order to reduce or eliminate the formation of axial air gaps that may otherwise form between bore wall 62 and bullet 10 adjacent rifling grooves.

Smoothbore barrel 19 may be sized to reduce or eliminate friction and in some cases to reduce or eliminate direct contact, with the bullet 10, during firing relative to a rifled barrel embodiment. A rifled barrel may have a narrower inner diameter than the bullet, in order to force the bullet to contact, and rotate relative to, the rifling grooves, however, when a smoothbore barrel is used, rotation does not depend on the presence of rifling grooves, so the inner diameter of the smoothbore barrel 19 may be increased relative to a rifled barrel, thus reducing friction on the bullet and relatively increasing muzzle velocity.

The indefinite articles "a" and "an" before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims. A bull et compri sing :. The bullet of claim 1 in which the base is shaped to cause the bullet to spin in a clockwise direction when viewing a base end of the bullet down the flight axis.

The bullet of any one of claim 1 - 2 in which the base is a closed circular end of the cylindrical body. The bullet of claim 3 in which the base defines a vane surface radially spaced from the flight axis and sloped relative to a plane defined perpendicular to the flight axis such that exposure, on the vane surface, to the axial force imparts a torque on the bullet in the rotational direction.

The bullet of claim 4 in which the base defines a plurality of vane surfaces angularly distributed about the flight axis relative to one another and each being respectively sloped relative to the plane defined perpendicular to the flight axis such that exposure, on each vane surface, to the axial force imparts a torque on the bullet in the rotational direction. The bullet of claim 5 in which the plurality of vane surfaces are angularly distributed about at least a periphery of the base.

The bullet of claim 6 in which a circumferential edge, defined between the base and the cylindrical body, follows the sloping of the plurality of vane surfaces.

The bullet of any one of claim 6 - 7 in which the plurality of vane surfaces connect radial end to radial end in a stepped fashion. The bullet of any one of claim 5 - 8 in which each vane surface forms a circular sector.

The bullet of claim 9 in which the plurality of vane surfaces comprises two semicircular sectors. The bullet of any one of claim 4 - 10 in which each vane surface is sloped with a helical shape. The bullet of any one of claim 4 - 10 in which each vane surface is sloped with a planar shape. The bullet of any one of claim 4 - 10 in which each vane surface is sloped with the shape of a cylindrical wall.

The bullet of any one of claim 1 - 13 in which the cylindrical body has a boat tail shape adjacent the base. A combination comprising a gun and the bullet of any one of claim 1 - 14 loaded in the gun, the gun having a barrel with a rifling path defined on an interior surface of the barrel, in which the rotational direction matches a twist direction of the rifling path.

A combination comprising a gun and the bullet of any one of claim 4 - 13 loaded in the gun, the gun having a barrel with a rifling path defined on an interior surface of the barrel, in which the rotational direction matches a twist direction of the rifling path, and each vane surface is sloped to form an angle of ninety degrees or less, with respect to a longitudinal leading edge of the rifling path, the angle being defined moving in the rotational direction from the longitudinal edge to the vane surface.

The combination of claim 16 in which each vane surface is sloped to form an angle of ninety degrees with respect to the longitudinal leading edge of the rifling path. A combination comprising a gun and the bullet of any one of claim 1 - 14 loaded in the gun, the gun having a smoothbore barrel.

A method comprising initiating a propellant explosion adjacent a base of a bullet loaded in a gun to propel the bullet down a barrel of the gun, in which the propellant explosion creates an axial force that acts upon a vane surface defined by the base of the bullet to generate a torque that causes the bullet to spin in a rotational direction about a flight axis defined by the bullet. The method of claim 19 in which the barrel comprises a rifling path whose twist direction matches the rotational direction.

USP true USA1 en. WOA1 en. USB2 en. USA en. USB1 en. PTE en. JPB2 en. Finless training projectile with improved flight stability over an extended range. A barrel will produce individual markings in addition to a bullet's land and groove impressions as the bullet passes through, and it is these unique markings that an examiner evaluates to determine whether a given bullet was fired from a particular firearm. To figure out if a bullet could have originated from a specific firearm, however, a forensic firearm and toolmark examiner uses an instrument called a comparison microscope to compare a questioned bullet one recovered from a crime scene, for example to bullets test fired from a suspect firearm.

Examiners generally test fire into a water recovery tank to obtain comparison bullets for evaluation under the microscope. A comparison microscope comprises two compound microscopes joined by an optical bridge and one set of eyepieces, or oculars. The configuration is such that the examiner can evaluate items on each of the microscope stages at the same time. A dividing line separates the two items in the field of view, and allows the examiner to vary how much of each item is observed simultaneously.

After evaluation of the test-fired bullets against one another for the presence of repetitive individual microscopic markings, the questioned bullet is mounted on the left stage and one of the test-fired bullets is placed on the right stage. The examiner then assesses the questioned bullet for the same repetitive marks that are present on the test projectiles. If sufficient correspondence is found between the questioned bullet and the test bullets, with no unexplainable differences, the examiner can conclude that the questioned bullet was fired from the suspect firearm.

The image above demonstrates corresponding microscopic markings consistent with two bullets having been fired from the same firearm. Sign up for our email newsletter. The earliest firearms had simple tubular bores, like a modern shotgun. In the late s, gunsmiths in what is now Germany developed a method of scraping grooves in barrels to allow room for blackpowder and lead fouling to build up, hopefully prolonging the accuracy of the barrels before they needed to be cleaned. They found, eventually, that by twisting these grooves in a barrel, they could dramatically improve its accuracy.

Rifling works by spinning the projectile about its axis, causing gyroscopic forces that spin-stabilize it throughout its flight; tighter rifling will spin a bullet faster, while looser rifling will spin a bullet slower.

The rate at which the bullet is spun is very closely tied to how stable it will be; too slow, and the bullet will tumble in the air, too fast and the bullet may break apart in flight. An M4 Carbine with a fairly new barrel firing 5.

The Firearm Blog is a news site dedicated to all things firearms related. TFB covers top stories in the firearms industry. TFB staff writers share a passion for firearms but come from a diverse background, stretching from the world of law enforcement to being deployed on the streets of Fallujah, Iraq to the woods hunting wild game. For the latest Police1 firearms product articles, check out a modern duty pistol for small cops , 10 families of great concealed carry firearms and our review of rail-mounted lights and lasers.

More Product news. More Product Originals. More Police Firearm Accessories Articles. All Distributors.