As the tank's primary armament, they are almost always employed in a direct fire mode to defeat a variety of ground targets at all ranges, including dug-in infantry, lightly armored vehicles, and especially other heavily armored tanks. They must provide accuracy, range, penetration, and rapid fire in a package that is as compact and lightweight as possible, to allow mounting in the cramped confines of an armored gun turret. Tank guns generally use self-contained ammunition, allowing rapid loading (or use of an autoloader). They often display a bulge in the barrel, which is a bore evacuator, or a device on the muzzle, which is a muzzle brake.