tail covert (of a bird); tail pipe (of a turbine); receiver (of a rifle)
canteen; flask; water bottle; thermos
(warning) flare (esp. used on roads and railways)
single barrel; single-barrelled
stun grenade (esp. the M84 stun grenade); flashbang
(chlorine) feeder tube; (ammunition) cartridge
cartridge (for a firearm)
multiple barrels; multi-barrel