Twist Rate
For best performance, the barrel should have a twist rate sufficient to spin stabilize any bullet that it would reasonably be expected to fire, but not significantly more. Large diameter bullets provide more stability, as the larger radius provides more gyroscopic inertia, while long bullets are harder to stabilize, as they tend to be very backheavy and the aerodynamic pressures have a longer "lever" to act on. The slowest twist rates are found in muzzleloading firearms meant to fire a round ball; these will have twist rates as low as 1 in 60 inches (1,500 mm), or slightly longer, although for a typical multi-purpose muzzleloader rifle, a twist rate of 1 in 48 inches (1,200 mm) is very common. The M16A2 rifle, which is designed to fire the 5.56x45mm NATO SS109 ball and L110 tracer bullets, has a 1 in 7-inch (177.8 mm) or 32 calibers twist. Civilian AR-15 rifles are commonly found with 1 in 12 inches (304.8 mm) or 54.8 calibers for older rifles and 1 in 9 inches (228.6 mm) or 41.1 calibers for most newer rifles, although some are made with 1 in 7 inches (177.8 mm) or 32 calibers twist rates, the same as used for the M16 rifle. Rifles, which generally fire longer, smaller diameter bullets, will in general have faster twist rates than handguns, which fire shorter, larger diameter bullets.
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Famous quotes containing the words twist and/or rate:
“The duce of any other rule have I to govern myself by in this affair—and if I had one ... I would twist it and tear it to pieces, and throw it into the fire when I had done—Am I warm? I am, and the cause demands it—a pretty story! is a man to follow rules—or rules to follow him?”
—Laurence Sterne (1713–1768)
“I don’t know but a book in a man’s brain is better off than a book bound in calf—at any rate it is safer from criticism. And taking a book off the brain, is akin to the ticklish & dangerous business of taking an old painting off a panel—you have to scrape off the whole brain in order to get at it with due safety—& even then, the painting may not be worth the trouble.”
—Herman Melville (1819–1891)