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Miller twist rule is a mathematical formula derived by American physical chemist and historian of science Donald G. Miller (1927-2012) to determine the rate of twist to apply to a given bullet to provide optimum stability using a rifled barrel. [1]
Example of a ballistic table for a given 7.62×51mm NATO load. Bullet drop and wind drift are shown both in mrad and MOA.. A ballistic table or ballistic chart, also known as the data of previous engagements (DOPE) chart, is a reference data chart used in long-range shooting to predict the trajectory of a projectile and compensate for physical effects of gravity and wind drift, in order to ...
Barrel time - the time from when the projectile starts to move until it exits the barrel. Diagram of internal ballistic phases. The burning firearm propellant produces energy in the form of hot gases that raise the chamber pressure which applies a force on the base of the projectile, causing it to accelerate. The chamber pressure depends on the ...
Dynamic pressure: Stagnation pressure: 0: Formula Result of #3 minus #2: Difference between #3 and #1: Sum of #1 and #2 Description What is typically understood as "pressure"; not influenced by velocity. Potential for pressure rise in fluid due to kinetic energy.
The energy conversion efficiency of a firearm strongly depends on its construction, especially on its caliber and barrel length. However, for illustration, here is the energy balance of a typical small firearm for .300 Hawk ammunition: [1] Barrel friction 2%; Projectile motion 32%; Hot gases 34%; Barrel heat 30%; Unburned propellant 1%.
However, the pressure rating used to determine if a round is +P is the peak pressure, which is not an accurate indication of the velocity, since it is the area under the pressure curve that determines the total energy imparted to the bullet (see internal ballistics). A large number of factors can impact the peak pressure of a load, such as:
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The external ballistics uses so-called initial velocity Vo, which is not the same as the real muzzle velocity. The initial velocity Vo is calculated via an extrapolation of the decaying part of velocity curve to the position of the muzzle (to). The difference between these two velocities is visible in the chart. [7]