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So, the muzzle velocity of a 2-inch (51 mm) barrel is less than that of a 4-inch (100 mm) barrel, which is less than that of a 6-inch (150 mm) barrel. Large naval guns will have high length-to-diameter ratios, ranging between 38:1 to 50:1. This length ratio maximizes the projectile velocity.
Since barrel length is limited by practical concerns to about arm's length for a rifle and much shorter for a handgun, increasing bore diameter is the normal way to increase the efficiency of a cartridge. The limit to bore diameter is generally the sectional density of the projectile (see external ballistics).
The length of the barrel (especially for larger guns) is often quoted in multiples of the caliber, used, for example, in US naval rifles 3 in (76 mm) or larger. [2] The effective length of the barrel (from breech to muzzle) is divided by the barrel diameter to give a dimensionless quantity.
The powder used in the Stinger increases velocity up to the longest .22 barrel length tested by the NRA, 26 in (660 mm). [23] Later hyper-velocity rounds were introduced by other makers, based on the long rifle case with lighter bullets in the 30-gr weight range and slow-burning rifle powder loadings. The overall length of many of these ...
Muzzle energy is dependent upon the factors previously listed, and velocity is highly variable depending upon the length of the barrel a projectile is fired from. [2] Also the muzzle energy is only an upper limit for how much energy is transmitted to the target, and the effects of a ballistic trauma depend on several other factors as well.
The M4's 14.5" barrel length reduces muzzle velocity to about 2900 ft/s. [193] This reduced wounding ability is one reason that, despite the Army's transition to short-barrel M4s, the Marine Corps has decided to continue using the M16A4 with its 20″ barrel as the 5.56×45mm M855 is largely dependent upon high velocity to wound effectively.
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%.
A 7.62 NATO round reaches 50 percent of its velocity within 80 mm (3.1 in) of the barrel when fired, so decreasing the barrel length for close quarters combat results in increased muzzle pressure and greater noise and muzzle flash.