gun barrel(n = noun.artifact) barrel - a tube through which a bullet travels when a gun is fired;
is a kind of tube, tubing
is a part of gun

ack-ack gun, air gun, antiaircraft gun, assault gun, barrel, barrel cactus, barrel knot, barrel maker, barrel organ, barrel process, barrel roll, barrel vault, bb gun, beer barrel, big gun, bofors gun, bren gun, browning machine gun, burp gun, electron gun, field gun, gas gun, gatling gun, golden barrel cactus, grease gun, gun, gun carriage, gun case, gun chamber, gun control, gun deck, gun dog, gun down, gun emplacement, gun enclosure, gun for, gun for hire, gun moll, gun muzzle, gun rest, gun room, gun smoke, gun trigger, gun turret, harpoon gun, high-angle gun, hired gun, hotchkiss gun, hydropneumatic gun carriage, jump the gun, krupp gun, light machine gun, machine gun, maxim gun, minute gun, naval gun, paintball gun, pickle barrel, pork barrel, quaker gun, rain barrel, rear of barrel, riot gun, set gun, smoking gun, spray gun, spring gun, squirt gun, staple gun, sten gun, stun gun, submachine gun, thompson submachine gun, tommy gun, trash barrel, vickers' gun, vickers-maxim automatic machine gun, vickers-maxim gun, water gun, whaling gun, whitworth gun, wine barrel, wire gun, wire-wound gun, zip gun