Wiktionary
n. A ventilated covering for the barrel of a firearm that prevents accidental burns to the operators
Wikipedia
A barrel shroud is a covering attached to the barrel of a firearm, that partially or completely encircles the barrel which prevents operators from injuring themselves on a hot barrel. Slides, extensions of the stock that do not fully encircle the barrel, and the receiver (or frame) of a firearm itself are generally not described as barrel shrouds, though they in fact do act as such. Barrel shrouds are commonly featured on air-cooled machine guns, where sustained rapid or automatic fire leave the barrel extremely hot and dangerous to the operator. However, shrouds can also be utilized on semi-automatic firearms, as even a small number of shots can heat up a barrel enough to injure an operator in certain circumstances.
Barrel shrouds are also used on pump-action shotguns. The military trench shotgun features a ventilated metal handguard with a bayonet attachment lug. Ventilated handguards or heat shields (usually without bayonet lugs) are also used on police riot shotguns and shotguns marketed for civilian self-defense. The heat shield also serves as an attachment base for accessories such as sights or sling swivels.
Usage examples of "barrel shroud".
The barrel shroud had a faint rainbow pattern from one of the times she'd used it in rain heavy enough to quench the hot steel.
In the middle of taking down the target Mike had noticed, from the ribbed feel of the barrel shroud, that the weapon was an MP-5 SD, one of the quietest silenced sub-guns in the world.
Unable to properly fidget because of the suit, he kicked a bit of detritus on the floor at his feet then recognized it as the barrel and barrel shroud of an M-16A2.