What is the name for the helical grooves in the barrel of a gun designed to impart spin on the projectile to improve its aerodynamic stability and accuracy?
"over an overshot card, and hand tools for putting a roll crimp on a paper shell were readily available and very inexpensive. Saboted slugs are shotgun projectiles smaller than the bore of the shotgun and supported by a plastic sabot. The sabot is traditionally designed to engage the rifling in a rifled shotgun barrel and impart a ballistic spin onto the projectile. This differentiates them from traditional slugs, which are not designed to benefit from a rifled barrel (though neither does the other any damage). Due to the fact that they do not contact the bore, they can be made"
"firearm. For this purpose, the traditional tool of the firearms examiner has been what is often called the ballistics comparison microscope. The interior of a gun's barrel is machined to have grooves (called rifling) that force the bullet to rotate as it travels along it. These grooves and their counterpart, called ""lands"" imprint groove and land impressions on the surface of the bullet. Together with these land and groove impressions, imperfections on the barrel surface are incidentally transferred to the bullet's surface. Because these imperfections are randomly generated, during manufacture or due to use, they are unique to each barrel."
"spin rate is beneficial to a fin-stabilized projectile, averaging out aerodynamic imbalances and improving accuracy. Even smooth-bore fired APFSDS projectiles incorporate fins that are slightly canted to provide some spin rate during flight; and very low twist rifled barrels have also been developed for the express purpose of firing APFSDS ammunition. Another reason for the use of smoothbore, and very low twist rate guns is that the most effective precision shaped charge designs, HEAT munitions, lose armor penetrating performance when rotating too fast. These deep penetrating shaped charges also require fin stabilization; (although less precise and less effective ""spin compensated"""
"Helical railgun Helical railguns are multi-turn railguns that reduce rail and brush current by a factor equal to the number of turns. Two rails are surrounded by a helical barrel and the projectile or re-usable carrier is also helical. The projectile is energized continuously by two brushes sliding along the rails, and two or more additional brushes on the projectile serve to energize and commute several windings of the helical barrel direction in front of and/or behind the projectile. The helical railgun is a cross between a railgun and a coilgun. They do not currently exist in a practical, usable"
"encountered with a ""gain twist"", where the rate of spin increases from chamber to muzzle. While intentional gain twists are rare, due to manufacturing variance, a slight gain twist is in fact fairly common. Since a reduction in twist rate is very detrimental to accuracy, gunsmiths who are machining a new barrel from a rifled blank will often measure the twist carefully so they may put the faster rate, no matter how minute the difference is, at the muzzle end. A barrel of circular bore cross-section is not capable of imparting a spin to a projectile, so a rifled barrel"
"Smoothbore A smoothbore weapon is one that has a barrel without rifling. Smoothbores range from handheld firearms to powerful tank guns and large artillery mortars. The majority of shotguns are smoothbores and the term can be synonymous. Early firearms had smooth barrels that fired projectiles without significant spin. To minimize inaccuracy-inducing tumbling during flight their projectiles required stable shape, such as a sphere. However, the Magnus effect causes even spheres rotating randomly during flight to curve when spinning on any axis not parallel to the direction of travel. Rifling a barrel with spiral grooves or polygonal rifling imparts a stabilizing"
"protrude more or less into the barrel, so that backspin is increased or reduced. Ideally, the hop-up should be adjusted so that the pellets fly as far as possible in a straight line without curving upward too far, or dropping to the ground too quickly. Hop-Up does decrease the velocity of the projectile (a gun firing with the hop fully unwound can drop to as low as ). Ease and location of adjustment varies by gun design; some equipment provide controls that can be adjusted quickly during gameplay, while others may require partial dis-assembly. For example, a common location for"
"barrel, placed between the propellant charge and the projectile. The name ""sabot"" (pronounced in English usage) is the French word for clog (a wooden shoe traditionally worn in some European countries). Concentration of force into a smaller area was initially attained by replacing the single metal (usually steel) shot with a composite shot using two metals, a heavy core (based on tungsten) inside a lighter metal outer shell. These designs were known as armour-piercing composite rigid (APCR) by the British, high-velocity armor-piercing (HVAP) by the US, and ""hartkern"" (hard core) by the Germans. On impact, the core had a much"
"even higher muzzle velocity than could be achieved with stubbier APDS projectiles. Armour-piercing discarding sabot (APDS) was initially the main design of the kinetic energy (KE) penetrator. The logical progression was to make the shot longer and thinner to concentrate the kinetic energy in a smaller area. However, a long, thin rod is aerodynamically unstable; it tends to tumble in flight and is less accurate. Traditionally, rounds were given stability in flight from the rifling of the gun barrel, which imparts a spin to the round. Up to a certain limit, this is effective, but once the projectile's length is"
"third attempt to replace the aging M2 Bradley. India has successfully tested their own railgun. Russia, China, and Turkey's defence company ASELSAN are also developing railguns. Helical railguns are multi-turn railguns that reduce rail and brush current by a factor equal to the number of turns. Two rails are surrounded by a helical barrel and the projectile or re-usable carrier is also helical. The projectile is energized continuously by two brushes sliding along the rails, and two or more additional brushes on the projectile serve to energize and commute several windings of the helical barrel direction in front of and/or"
"certain rpm before centrifugal forces cause a safety feature to disengage or move an arming mechanism to its armed position. Artillery shells are fired through a rifled barrel, which forces them to spin during flight. In other cases the bomb, mine or projectile has a fuze that prevents accidental initiation e.g. stopping the rotation of a small propeller (unless a lanyard pulls out a pin) so that the striker-pin cannot hit the detonator even if the weapon is dropped on the ground. These types of fuze operate with aircraft weapons, where the weapon may have to be jettisoned over ""friendly"""
"all for a fairly small gain in velocity and energy over other .22 caliber cartridges. Nearly all small bore firearms, with the exception of shotguns, have rifled barrels. The rifling imparts a spin on the bullet, which keeps it from tumbling in flight. The rifling is usually in the form of sharp edged grooves cut as helices along the axis of the bore, anywhere from 2 to 16 in number. The areas between the grooves are known as lands. Another system, polygonal rifling, gives the bore a polygonal cross section. Polygonal rifling is not very common, used by only a"
"steadily moving the target from where it was at launch time. Two methods can be employed to stabilize non-spherical projectiles during flight: The effect of gravity on a projectile in flight is often referred to as projectile drop or bullet drop. It is important to understand the effect of gravity when zeroing the sighting components of a gun. To plan for projectile drop and compensate properly, one must understand parabolic shaped trajectories. In order for a projectile to impact any distant target, the barrel must be inclined to a positive elevation angle relative to the target. This is due to"
"any rifled gun. However, the centrifugal force of a spinning shell disperses the charged jet. Thus, most hollow charge projectiles are fin-stabilized and not spin-stabilized. In recent years, it has become possible to use shaped charges in spin-stabilized projectiles by imparting an opposite spin on the jet so that the two spins cancel out and result in a non-spinning jet. This is done either using fluted copper liners, which have raised ridges, or by forming the liner in such a way that it has a crystalline structure which imparts spin to the jet. Besides spin-stabilization, another problem with any barreled"
"gyroscopic spin to a projectile that prevents tumbling in flight. Not only does this more than counter Magnus-induced drift, but it allows a longer, heavier round to be fired from the same caliber barrel, increasing both range and power. In the eighteenth century, the standard infantry arm was the smoothbore musket; although rifled muskets were introduced in the early 18th century and had more power and range, they did not become the norm until the middle of the 19th century, when the Minié ball increased their rate of fire to match that of smoothbores. Artillery weapons were smoothbore until the"
"the rifling grooves, unlike the loose-fitting and inaccurate musket ball. This was achieved by including a deep cavity in the rear, into which fitted (initially) an iron hemispherical cup, later a conical clay or timber plug, which caused the base of the projectile to expand upon firing, sealing the skirt to the bore, allowing an undersized projectile to be used for ease of loading without a patch. (Eventually it was found that the pressure of the powder gases expanded the base to fit the bore, without any plug or filler.) Another was a number of grooves around the projectile, the"
"Rotation of ammunition Rotation of ammunition is a term used with reference to guns. Projectiles intended for RML (rifled muzzle-loading) guns were at first fitted with a number of gun-metal studs arranged around them in a spiral manner corresponding to the twist of rifling. This was defective, as it allowed, as in the old smooth-bore guns, the powder gas to escape by the clearance (called ""windage"") between the projectile and the bore, with a consequent loss of efficiency; it also quickly eroded the bore of the larger guns. Later the rotation was effected by a cupped copper disc called an"
"numerous bullets strike. Synchronization gear A synchronization gear, or a gun synchronizer, sometimes rather less accurately called an interrupter, is attached to the armament of a single-engine tractor-configuration aircraft so it can fire through the arc of its spinning propeller without bullets striking the blades. The idea presupposes a fixed armament directed by aiming the aircraft in which it is fitted at the target, rather than aiming the gun independently. There are many practical problems, mostly arising from the inherently imprecise nature of an automatic gun's firing, the great (and varying) velocity of the blades of a spinning propeller, and"
"form. A helical railgun was built at MIT in 1980 and was powered by several banks of, for the time, large capacitors (approximately 4 farads). It was about 3 meters long, consisting of 2 meters of accelerating coil and 1 meter of decelerating coil. It was able to launch a glider or projectile about 500 meters. Helical railgun Helical railguns are multi-turn railguns that reduce rail and brush current by a factor equal to the number of turns. Two rails are surrounded by a helical barrel and the projectile or re-usable carrier is also helical. The projectile is energized continuously"
"considerably better aerodynamics than the original; its spin was moderated by fins on the shell rather than by rifling in the barrel only and the round was supported in the gun barrel by four aerodynamic nubs allowing the middle of the shell to be elongated and thus reducing drag. The shell was initially spun in the same way as conventional artillery rounds with a driving band towards the base. The result was a gun that could out-range the original by as much as 30%, while at the same time being much more accurate. Standard NATO and US artillery of the"
"The primary factors affecting the aerodynamics of a bullet in flight are the bullet's shape and the rotation imparted by the rifling of the gun barrel. Rotational forces stabilize the bullet gyroscopically as well as aerodynamically. Any asymmetry in the bullet is largely canceled as it spins. However, a spin rate greater than the optimum value adds more trouble than good, by magnifying the smaller asymmetries or sometimes resulting in the bullet exploding midway in flight. With smooth-bore firearms, a spherical shape was optimum because no matter how it was oriented, it presented a uniform front. These unstable bullets tumbled"
"differentiated to fire either single or multiple projectiles. Single projectiles were used for larger game, though shot could be loaded as needed for small game and birds. As firearms became specialized and differentiated, shotguns were still able to fire round balls though rifled muskets were far more accurate and effective. Modern slugs emerged as a way of improving on the accuracy of round balls. Early slugs were heavier in front than in the rear, similar to a Minié ball to provide aerodynamic stabilization. Rifled barrels, or rifled choke tubes were developed later to provide gyroscopic spin stabilization in place of"
"Hop-up (airsoft) Hop-up is the back-spin put on airsoft pellets and BBs to increase their range via the Magnus effect. Hop-up devices apply backspin to the projectile reducing the air pressure on its top side. This causes the plastic pellet to fall less over a given distance than it would without the spin applied, extending the effective range of the weapon without increasing velocity. In airsoft guns, this is usually implemented as a projection (called a bucking) into the path of the projectile, on the top of the barrel. The bucking momentarily hinders the top side of the projectile, imparting"
"monoblock steel cannon. HEAT warheads suffer when spin stabilized, a product of rifled barrels, causing the French to develop the Obus G, (Gresse). This projectile was composed of two major parts, including the outer shell and a suspended inner shell, divided by ball bearings. This allowed the projectile to be spin-stabilized, and therefore more accurate than a normal fin-stabilized HEAT-round, while the inner shell did not move, allowing the warhead to work at maximum efficiency. The warhead, containing 780 gram hexolite, could penetrate up to of steel armour and was effective against tanks at up to . As it combined"
"confusion; for example, the projectiles of the .303 British are actually slightly larger in diameter than the projectiles of the .308 Winchester, because the "".303"" refers to the bore diameter in inches (bullet is .312), while the "".308"" refers to the bullet diameter in inches (7.92 mm and 7.82 mm, respectively). Despite differences in form, the common goal of rifling is to deliver the projectile accurately to the target. In addition to imparting the spin to the bullet, the barrel must hold the projectile securely and concentrically as it travels down the barrel. This requires that the rifling meet a"
"Synchronization gear A synchronization gear, or a gun synchronizer, sometimes rather less accurately called an interrupter, is attached to the armament of a single-engine tractor-configuration aircraft so it can fire through the arc of its spinning propeller without bullets striking the blades. The idea presupposes a fixed armament directed by aiming the aircraft in which it is fitted at the target, rather than aiming the gun independently. There are many practical problems, mostly arising from the inherently imprecise nature of an automatic gun's firing, the great (and varying) velocity of the blades of a spinning propeller, and the very high"
"a throwback to the earliest types of rifling, has become popular, especially in handguns. Polygonal barrels tend to have longer service lives because the reduction of the sharp edges of the land (the grooves are the spaces that are cut out, and the resulting ridges are called lands) reduces erosion of the barrel. Supporters of polygonal rifling also claim higher velocities and greater accuracy. Polygonal rifling is currently seen on pistols from CZ, Heckler & Koch, Glock, Tanfoglio, and Kahr Arms, as well as the Desert Eagle. For tanks and artillery pieces, the extended range, full bore concept developed by"
"Chipmunk. Ventral or dorsal fins increasing the directional stability are also used as anti-spin devices. Certain air-deployed munitions, particularly ""dumb"" or unguided 500-pound bombs, are often retrofitted with bolt-on strake sets. Designed as an open collar with strakes fitted to the outside face, these strake sets are used to alter and normalize the aerodynamics of the weapon, yielding greater accuracy. As most such munitions were manufactured with only tail-mounted stabilizer fins, the addition of longitudinal strakes proves a much cleaner flow of air around the weapon during its glide, reducing the tendency to yaw and improving terminal accuracy. Strakes are"
"subjected to the greatest thermomechanical stress and therefore suffers wear the fastest. Throat erosion is often the main determining factor of a gun's barrel life. The muzzle is the front end of barrel from which the projectile will exit. Precise machining of the muzzle is crucial to accuracy, because it is the last point of contact between the barrel and the projectile. If inconsistent gaps exist between the muzzle and the projectile, escaping propellant gases may spread unevenly and deflect the projectile from its intended path (see transitional ballistics). The muzzle can also be threaded on the outside to allow"
"on the base of the bullet, which will disrupt its flight. The muzzle end of the barrel is called the ""crown"", and it is usually either beveled or recessed to protect it from bumps or scratches that might affect accuracy. A sign of a good crown will be a symmetric, star-shaped pattern on the muzzle end of the barrel, formed by soot deposited, as the powder gases escape the barrel. If the star is uneven, then it is a sign of an uneven crown, and an inaccurate barrel. Before the barrel can release the bullet in a consistent manner, it"
"on the ""Polygroove"" pattern with 24 grooves and projectiles had ""Automatic gas-checks"" attached to the base which engaged the grooves. Three planes were machined on the upper surface of the Howitzer, for use with quadrants enabling it to be elevated to 30 degrees. This enabled the gun to be sighted for indirect, or direct fire. 46- and 70 cwt guns differed in number and type of rifling grooves so studded projectiles were only available for 46 cwt guns, and different automatic gas checks were required for studless projectiles. Guns were fired using a silk bag containing a black powder propellant."
"at longer ranges (1,500–2,000 m). In an effort to gain better aerodynamics APC rounds were given a ballistic cap to improve muzzle velocity and reduce drag. The hollow ballistic cap would break away when the projectile hit the target. These rounds were classified as (APBC) or armor-piercing ballistic capped rounds. Due to the increase in armor thickness during WWII, the projectiles’ size and impact velocity had to be increased to ensure perforation. At these higher velocities, the hardened tip of the shot or shell has to be protected from the initial impact shock, or risk shattering. To raise the impact"
"whilst the pellet is still within the barrel. Spring gun recoil also has a sharp forward component, caused by the piston hitting the front end of the pump chamber when the spring has fully decompressed. These two rapid jerking movements are known to damage scopes not rated for spring gun usage. In addition, the spring vibrations are often unpredictable and can also cause accuracy to suffer. These vibrations can be controlled by adding features like close-fitting spring guides or by aftermarket tuning done by ""airgunsmiths"" who specialize in air gun modifications, a common one being the addition of viscous silicone"