# Gun chronograph

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A Down Range chronograph with storage and statistical tools.

A gun chronograph or shooting chronograph is an instrument used to measure the velocity of a projectile fired by a gun.

## History

Benjamin Robins (1707–1751) invented the ballistic pendulum that measures the momentum of the projectile fired by a gun. Dividing the momentum by the projectile mass gives the velocity. Robbins published his results as New Principles of Gunnery in 1742. [1] [2] The ballistic pendulum could make only one measurement per firing because the device catches the projectile. [3] The gun's accuracy also limited how far down range a measurement could be made. [4]

Benjamin Robins was a pioneering English scientist, Newtonian mathematician, and military engineer.

A ballistic pendulum is a device for measuring a bullet's momentum, from which it is possible to calculate the velocity and kinetic energy. Ballistic pendulums have been largely rendered obsolete by modern chronographs, which allow direct measurement of the projectile velocity.

In Newtonian mechanics, linear momentum, translational momentum, or simply momentum is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction in three-dimensional space. If m is an object's mass and v is the velocity, then the momentum is

An early chronograph that measures velocity directly was built in 1804 by Grobert, a colonel in the French Army. This used a rapidly rotating axle with two disks mounted on it about 13 feet apart. The bullet was fired parallel to the axle, and the angular displacement of the holes in the two disks, together with the rotational speed of the axle, yielded the bullet velocity. [5]

Grobert is a surname. Notable people with the surname include:

Ingalls (1886 , p. 18) describes Bashforth's chronograph that could make many measurements over long distances:

In 1865 the Rev. Francis Bashforth, M. A., who had then been recently appointed Professor of Applied Mathematics to the advanced class of artillery officers at Woolwich, began a series of experiments for determining the resistance of the air to the motion of both spherical and oblong projectiles, which he continued from time to time until 1880. As the instruments then in use for measuring velocities were incapable of giving the times occupied by a shot in passing over a series of successive equal spaces, he began his labors by inventing and constructing a chronograph to accomplish this object, which was tried late in 1865 in Woolwich Marshes, with ten screens, and with perfect success.

The Bashforth screens were made with several threads and series connected switches. A projectile passing through a screen would break one or more threads, the broken thread caused a switch to momentarily (about 20 ms) interrupt a current as the switch arm moved from its weighted position to its unweighted position, and the momentary interruption would be recorded on a paper chart. [6]

## Modern chronograph

The modern chronograph consists of two sensing areas called chronograph screens, which contain optical sensors that detect the passage of the bullet. The bullet is fired so it passes through both screens, and the time it takes the bullet to travel the distance between the screens is measured electronically.

Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. A photo detector has a p–n junction that converts light photons into current. The absorbed photons make electron–hole pairs in the depletion region. Photodiodes and photo transistors are a few examples of photo detectors. Solar cells convert some of the light energy absorbed into electrical energy.

The first electronic ballistic chronograph was invented by Kiryako ("Jerry") Arvanetakis in the 1950s.[ citation needed ] As consulting engineer under contract by NACA (later NASA), he was asked to find a way to accurately measure the velocity of various projectiles fired at hyper-velocities into a variety of engineered materials in anticipation of manned space flight. His first design was an open rectangular frame of square aluminum tubing with a screen of fine copper wire at both ends. Breaking the first wire started charging a capacitor, breaking the second wire stopped it. Measuring the accumulated voltage and knowing the rate of charge the elapsed time could be accurately calculated.

The National Aeronautics and Space Administration is an independent agency of the United States Federal Government responsible for the civilian space program, as well as aeronautics and aerospace research.

A capacitor is a passive two-terminal electronic component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The capacitor was originally known as a condenser or condensator. The original name is still widely used in many languages, but not commonly in English.

## Related Research Articles

A rifle is a portable, long-barrelled firearm designed for long-range precision shooting, to be held with both hands and braced against the shoulder for stability during firing, and with a barrel that has a helical pattern of grooves ("rifling") cut into the bore walls. The term was originally rifled gun, with the word "rifle" referring to the machining process of creating grooving with cutting tools, and is now used for any long handheld device designed for aimed discharge activated by a trigger, such as air rifles and the personnel halting and stimulation response rifle. Rifles are used in warfare, law enforcement, hunting and shooting sports.

A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force acting on the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. The period depends on the length of the pendulum and also to a slight degree on the amplitude, the width of the pendulum's swing.

Recoil is the backward movement of a gun when it is discharged. In technical terms, the recoil momentum acquired by the gun exactly balances the forward momentum of the projectile and exhaust gases (ejecta), according to Newton's third law, known as conservation of momentum. In hand-held small arms, the recoil momentum is transferred to the ground through the body of the shooter; while in heavier guns such as mounted machine guns or cannons, recoil momentum is transferred to the ground through the mount.

Ballistics is the field of mechanics that deals with the launching, flight, behavior, and effects of projectiles, especially bullets, unguided bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.

External ballistics or exterior ballistics is the part of ballistics that deals with the behavior of a projectile in flight. The projectile may be powered or un-powered, guided or unguided, spin or fin stabilized, flying through an atmosphere or in the vacuum of space, but most certainly flying under the influence of a gravitational field.

A gun barrel is a crucial part of gun-type ranged weapons such as small firearms, artillery pieces and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high-pressure gas(es) is introduced behind a projectile in order to propel it out of the front end (muzzle) at a high velocity. The hollow interior of the barrel is called the bore. The measurement of the diameter of the bore is called the caliber. Caliber is usually measured in inches or millimetres.

A gunshot is a single discharge of a gun, typically a man-portable firearm, producing a visible flash, a powerful and loud shockwave and often chemical gunshot residue. The term can also refer to a ballistic wound caused by such a discharge.

Body armor/armour, personal armor/armour, suits of armour or coats of armour all refer to protective clothing, designed to absorb and/or deflect slashing, bludgeoning and penetrating attacks by weapons. It was historically used to protect military personnel, whereas today, it is also used to protect various types of police, private citizens, private security guards or bodyguards. Today there are two main types: regular non-plated personal armor and hard-plate reinforced personal armor, which is used by combat soldiers, police tactical units, private citizens, and hostage rescue teams.

In ballistics, the elevation is the angle between the horizontal plane and the axial direction of the barrel of a gun, mortar or heavy artillery. Originally, elevation was a linear measure of how high the gunners had to physically lift the muzzle of a gun up from the gun carriage to compensate for projectile drop and hit targets at a certain distance.

In ballistics, the ballistic coefficient (BC) of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to the negative acceleration: a high number indicates a low negative acceleration—the drag on the vehicle or projectile is small in proportion to its mass.

Gun laying is the process of aiming an artillery piece, such as a gun, howitzer, or mortar, on land or at sea, against surface or air targets. It may be laying for direct fire, where the gun is aimed similarly to a rifle, or indirect fire, where firing data is calculated and applied to the sights. The term includes automated aiming using, for example, radar-derived target data and computer-controlled guns.

The .41 Rimfire Cartridge was first introduced by the National Arms Company in 1863 and was also known as the .41 Short and the .41-100. In most designations like this, the second number refers to the black powder load, though in this case it means "41 hundredths of an inch".

The .408 Cheyenne Tactical designated 408 Chey Tac (10.36×77mm) by the C.I.P. is a specialized rimless, bottlenecked, centerfire cartridge for military long-range sniper rifles that was developed by Dr. John D. Taylor and machinist William O. Wordman. The round was designed with a possible military need for a cartridge for anti-personnel, anti-sniper and anti-materiel roles with a (supersonic) precision range of 2,200 yards. It is offered as a competitor to the most common military NATO long-range service cartridges such as .338 Lapua Magnum and the .50 BMG.

QuickLOAD is an internal ballistics predictor computer program for firearms.

The spitzer bullet, also commonly referred to as a spire point bullet, is primarily a small arms ballistics development of the late 19th and early 20th century, driven by military desire for aerodynamic bullet designs that will give a higher degree of accuracy and kinetic efficiency, especially at extended ranges. To achieve this, the projectile must minimize air resistance in flight.

The Aberdeen chronograph was the first portable gun chronograph, an instrument for measuring the muzzle velocity and striking power of a projectile fired by a gun. It was invented in 1918 by Alfred Lee Loomis at the U.S. Army's Aberdeen Proving Ground.

A gun is a ranged weapon typically designed to pneumatically discharge projectiles that are solid but can also be liquid or even charged particles and may be free-flying or tethered.

Francis Bashforth was a British applied mathematician who studied ballistics.

## References

1. Ingalls 1886 , p. 17
2. Robins, Benjamin (1805), New Principles of Gunnery (New ed.), F. Wingrave
3. Bashforth 1866 , p. 3, "only one observation on each round".
4. Bashforth 1866 , p. 3, "Beyond 295 feet the gun was not sufficiently accurate".
5. Prony (1805), "Report of a method of measuring the initial Velocity of Projectiles discharged from Fire-arms, both horizontally and with different Elevations, made to the Physical and Mathematical Class of the National Institute", in Nicholson, William, A Journal of Natural Philosophy, Chemistry and the Arts, XI, London at page 42
abridged from Journal des Mines No 92 p. 117, May 1804.
6. Bashforth 1866 , pp. 12–13