Pressure
Energy is imparted to the bullet in a firearm by the pressure of the gases produced by the burning gunpowder. While it seems to casual observers that a higher peak pressures should produce higher velocities, that is not always the case, since measures of peak pressure capture only a small fraction of the time the bullet is accelerating. To achieve maximum performance, the entire duration of the bullet's travel through the barrel must be considered.
There are hundreds of powders in existence because powders must be carefully matched to the case volume, case dimensions, bullet dimensions, bullet weight, barrel length, and special bullet features such as moly coating or driving bands. For example, long, heavy bullets are required to be seated so deep in the case that they displace powder, while at the same time requiring a slower powder which gives their greater mass more time to move down the barrel. If the bullet is banded or coated with a lubricant like moly, faster powders can be used as the bullet moves faster due to decreased friction with the barrel. All of these variables must be accommodated within the maximum pressure levels set for the platform. Finding the optimum combination is largely a trial and error process, and may take years to complete. New cartridges with significantly new internal ballistics often bring forth new powders engineered to maximize performance; examples of this are Accurate Arms 2230, designed for use in the .223 Remington, and #9, designed for use in magnum pistol cartridges.
Read more about this topic: Internal Ballistics
Famous quotes containing the word pressure:
“Much of the pressure contemporary parents feel with respect to dressing children in designer clothes, teaching young children academics, and giving them instruction in sports derives directly from our need to use our children to impress others with our economic surplus. We find “good” rather than real reasons for letting our children go along with the crowd.”
—David Elkind (20th century)
“We believe that civilization has been created under the pressure of the exigencies of life at the cost of satisfaction of the instincts.”
—Sigmund Freud (1856–1939)
“Today’s pressures on middle-class children to grow up fast begin in early childhood. Chief among them is the pressure for early intellectual attainment, deriving from a changed perception of precocity. Several decades ago precocity was looked upon with great suspicion. The child prodigy, it was thought, turned out to be a neurotic adult; thus the phrase “early ripe, early rot!””
—David Elkind (20th century)