A member of the art department, the armourer is the person who is in charge of the supply and supervision of all weapons on set. Weapons include things such as firearms, swords, and sometimes related items such as squibs. In most countries the armourer must hold appropriate licenses to handle these items.
More information on the job of an armourer, and the safety considerations of using firearms on set, can be found at the web site of Australian armour John Fox.