The ballistic coefficient jsb (abbreviated BC) of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to negative acceleration: a larger number indicates less negative acceleration, and the projectile's drag is directly proportional to its mass.
A little story
In 1537, Niccolò Tartaglia fired several test shots to determine the maximum angle and range of a bullet. Tartaglia came to the conclusion that the angle is 45 degrees. The mathematician noted that the trajectory of the shot is constantly bending.
In 1636, Galileo Galilei published his results in Dialogues on the Two New Sciences. He discovered that a falling body has a constant acceleration. This allowed Galileo to show that the trajectory of the bullet was curved.
Around 1665, Isaac Newton discovered the law of air resistance. Newton used air and liquids in his experiments. He showed that the resistance to a shot increases in proportion to the density of the air (or liquid), the cross-sectional area, and the weight of the bullet. Newton's experiments were carried out only at low speeds - up to about 260 m/s (853ft/s).
In 1718, John Keel challenged Continental Mathematics. He wanted to find the curve that the projectile could describe in the air. This problem assumes that air resistance increases exponentially with projectile speed. Keel could not find a solution to this difficult task. But Johann Bernoulli undertook to solve this difficult problem and soon after found the equation. He realized that air resistance varied like "any force" of speed. Later this proof became known as "Bernoulli's equation". It is this that is the forerunner of the concept of the "standard projectile".
Historical inventions
In 1742, Benjamin Robins created the ballistic pendulum. It was a simple mechanical device that could measure the speed of a projectile. Robins reported bullet velocities from 1400 ft/s (427 m/s) to 1700 ft/s (518 m/s). In his book New Principles of Shooting, published the same year, he used Euler's numerical integration and found that air resistance "varies as the square of the projectile's speed."
In 1753, Leonhard Euler showed how theoretical trajectories could be calculated using Bernoulli's equation. But this theory can only be used for resistance, which changes as the square of speed.
In 1844, the electroballistic chronograph was invented. In 1867, this device showed the time of flight of a bullet with an accuracy of one tenth of a second.
Test run
In many countries and their armedforces since the mid-18th century, test shots have been carried out using large ammunition to determine the resistance characteristics of each individual projectile. These individual test experiments were recorded in extensive ballistic tables.
Serious tests were carried out in England (Francis Bashforth was the tester, the experiment itself was carried out on Woolwich Marshes in 1864). The projectile developed a speed of up to 2800 m / s. Friedrich Krupp in 1930 (Germany) continued testing.
The shells themselves were solid, slightly convex, the tip had a conical shape. Their sizes ranged from 75 mm (0.3 inches) with a weight of 3 kg (6.6 pounds) to 254 mm (10 inches) with a weight of 187 kg (412.3 pounds).
Methods and standard projectile
Many militaries before the 1860s used the method of calculus in order to correctly determine the trajectory of a projectile. This method, which was suitable for calculating only one trajectory, was performed manually. In order to make calculations much easier and faster, research has begun to create a model of theoretical resistance. Research has led to a significant simplification of experimental processing. This was the "standard projectile" concept. Ballistic tables were compiled for a contrived projectile with a given weight and shape, specific dimensions and a certain caliber. This made it easier to calculate the ballistic coefficient of a standard projectile that could move through the atmosphere according to a mathematical formula.
Tableballistic coefficient
The above ballistic tables usually include such functions as: air density, time of flight of the projectile in range, range, degree of departure of the projectile from a given trajectory, weight and diameter. These figures facilitate the calculation of ballistic formulas, which are needed in order to calculate the muzzle velocity of the projectile in the range and flight path.
Bashforth barrels from 1870 fired a projectile at a speed of 2800 m/s. For calculations, Mayevsky used the Bashfort and Krupp tables, which included up to 6 restricted access zones. The scientist conceived a seventh restricted zone and stretched the Bashfort shafts up to 1100 m/s (3,609 ft/s). Mayevsky converted the data from imperial units to metric (currently SI units).
In 1884, James Ingalls submitted his barrels to the US Army Ordnance Circular using Mayevsky tables. Ingalls expanded the ballistic barrels to 5000 m/s, which were within the eighth restricted zone, but still with the same value of n (1.55) as Mayevsky's 7th restricted zone. Already fully improved ballistic tables were published in 1909. In 1971, the Sierra Bullet company calculated their ballistic tables for 9 limited zones, but only within 4,400 feet per second (1,341 m / s). This zone has lethal force. Imagine a 2 kg projectile traveling at 1341 m/s.
Majewski method
We have already mentioned a little abovethis surname, but let's consider what kind of method this person came up with. In 1872 Mayevsky published a report on the Trité Balistique Extérieure. Using his ballistic tables, along with Bashforth's tables from the 1870 report, Mayevsky created an analytical mathematical formula that calculated the air resistance for the projectile in terms of log A and the value of n. Although the scientist used a different approach in mathematics than Bashforth, the resulting calculations of air resistance were the same. Mayevsky proposed the concept of a limited zone. While exploring, he discovered the sixth zone.
Around 1886, the general published the results of a discussion of the experiments of M. Krupp (1880). Although the projectiles used varied widely in calibers, they had basically the same proportions as the standard projectile, 3 meters long and 2 meters in radius.
Siacci method
In 1880 Colonel Francesco Siacci published his Balistica. Siacci suggested that air resistance and density increase as the projectile speed increases.
The Siacci method was intended for flat fire trajectories with deflection angles of less than 20 degrees. He found that such a small angle did not allow the air density to have a constant value. Using the tables of Bashforth and Mayevsky, Siacci created a 4-zone model. Francesco used a standard projectile that General Mayevsky created.
Bullet Coefficient
Bullet Coefficient (BC) is basically a measure ofhow rationalized the bullet is, that is, how well it cuts through the air. Mathematically, this is the ratio of the bullet's specific gravity to its shape factor. Ballistic coefficient is essentially a measure of air resistance. The higher the number, the lower the resistance, and the more effective the bullet is through the air.
One more meaning - BC. The indicator determines the trajectory and drift of the wind when other factors are equal. BC changes with the shape of the bullet and the speed at which it travels. "Spitzer", which means "pointed", is a more effective shape than "round nose" or "flat point". At the other end of the bullet, the boat's tail (or tapered foot) reduces air resistance compared to a flat base. Both increase bullet BC.
Bullet Range
Of course, each bullet is different and has its own speed and range. A rifle shot at an angle of about 30 degrees will give the longest flight distance. This is a really good angle as an approximation to optimal performance. Many people assume that 45 degrees is the best angle, but it's not. The bullet is affected by the laws of physics and all natural forces that can interfere with an accurate shot.
After the bullet leaves the keg, gravity and air resistance begin to work against the starting energy of the muzzle wave, and lethal force develops. There are other factors, but these two have the most impact. As soon as the bullet leaves the barrel, it begins to lose horizontal energy due to air resistance. Some people will tell you that the bullet rises when it leaves the barrel, but this is only true if the barrel was placed at an angle when fired, which is often the case. If you fire horizontally towards the ground and throw the bullet upwards at the same time, both projectiles will hit the ground at almost the same time (minus the slight differential caused by the curvature of the ground and the slight drop in vertical acceleration).
If you aim your weapon at an angle of about 30 degrees, the bullet will travel much further than many people think, and even a low-energy weapon like a pistol will send the bullet over one mile. A projectile from a high-powered rifle can travel approximately 3 miles in 6-7 seconds, so you should never shoot into the air.
Ballistic coefficient of pneumatic bullets
Pneumatic bullets were not designed to hit a target, but to stop a target or do some minor physical damage. In this regard, most bullets for pneumatic weapons are made of lead, since this material is very soft, light and gives the projectile a small initial velocity. The most common types of bullets (calibers) are 4.5 mm and 5.5. Of course, larger-caliber ones were also created - 12.7 mm. Making a shot from such pneumatics and such a bullet, you need to think about the safety of strangers. For example, ball-shaped bullets are made for recreational play. In most cases, this type of projectile is coated with copper or zinc to avoid corrosion.
