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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]
= where is the muzzle velocity and is the twist rate. [15] For example, an M4 Carbine with a twist rate of 1 in 7 inches (177.8 mm) and a muzzle velocity of 3,050 feet per second (930 m/s) will give the bullet a spin of 930 m/s / 0.1778 m = 5.2 kHz (314,000 rpm).
The Model 1868 was also the first trapdoor conversion to use the cartridge extractor covered by U.S. Patent No. 68,009, issued August 27, 1867 to W.H. & G.W. Miller. The Model 1868 had an overall length of 51 7 ⁄ 8 inches. [1] Over 50,000 Model 1868 rifles were manufactured, chambered for the .50-70 450 cartridge.
Firearm muzzle velocities range from approximately 120 m/s (390 ft/s) to 370 m/s (1,200 ft/s) in black powder muskets, [3] to more than 1,200 m/s (3,900 ft/s) [4] in modern rifles with high-velocity cartridges such as the .220 Swift and .204 Ruger, all the way to 1,700 m/s (5,600 ft/s) [5] for tank guns firing kinetic energy penetrator ammunition.
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 ]
Springfield Model 1866 breech. The Springfield Model 1866 was the second iteration of the Allin-designed trapdoor breech-loading mechanism. Originally developed as a means of converting rifle muskets to breechloaders, the Allin modification ultimately became the basis for the definitive Springfield Model 1873, the first breech-loading rifle adopted by the United States War Department for ...
The second reference drag curve is adjusted to equal the Siacci/Mayevski retardation rate function at a projectile velocity of 2600 fps (792.5 m/s) using a .30-06 Springfield Cartridge, Ball, Caliber .30 M2 152 grains (9.8 g) rifle spitzer bullet with a slope or deceleration constant factor of 0.5 in the supersonic flight regime. In other ...
Rate of fire may also be affected by ergonomic factors. For rifles, ease-of-use features such as the design of the bolt or magazine release can affect the rate of fire. For artillery pieces, a gun on a towed mount can usually achieve a higher rate of fire than the same weapon mounted within the cramped confines of a tank or self-propelled gun ...