The longer the gun barrel, the greater the velocity of the projectile. Other factors that affect muzzle velocity are weapon caliber and ammunition type. The general rule of thumb is that 25 feet per second is lost for each inch taken away from the barrel.
There is some debate around this rule in the firearms community, but academic studies and clinical tests provide enough empirical data to support the 25 feet per second average. There are, however, many in hunting and firearm circles who think the studies are incorrect. Individual users cite personal tests performed at private ballistic ranges and state average losses well below the 25 feet per second rule, but fail to provide hard data to back up their statements.
Greater accuracy and flatter bullet trajectory are the other benefits of long barreled weapons. However, larger barrel size is not always desirable. It tends to make the weapon heavier and less maneuverable. Short-barreled weapons are lighter and offer increased mobility, but they have decreased accuracy and much louder reports when fired. The loudness of a shorter barrel’s report is thought to be due to the propellant’s charge, which is still expanding with the projectile as it exits the barrel. This gaseous expansion can be seen when the gun is fired and is known as muzzle blast.
Hunting rifles, such as the Remington 798, are long barreled weapons. Carbines, such as the M4, are short barreled rifles with military applications. They are effective in close quarters and urban settings. Handguns, including the Colt .45 and the Glock 9mm, have short barrels and low muzzle velocities. They have many uses in law enforcement and personal defense.