Handguard

A handguard on firearms is a guard attached to the front of a firearm to grip the weapon from the front. It allows the user protection from the barrel, which may become very hot when firing. It also gives room for more attachments to the weapon itself, such as an M203 grenade launcher.

A handguard (also known as the quillons, crossguard or crosstree) is also a part of a sword or knife that is just above the handle. It protects the wielder's hands from an opponent's blade should it happen to slide down the blade.

...
Wikipedia