I noticed that there is no word meaning firearm according to this site.Why is this? I've tried synonyms such as gun and pistol but none work. Has no one gotten around to making one?
It pains me to suggest that Latin Wikipedia is in error, but Latin Wikipedia is in error. The arma ignifera Nathanial suggests is in fact a word for firearm that some have used, but it's in the silva of the Morgan lexicon, not the adumbratio. The difference between the two is explained in a short piece by the lexicon's current editor, Patrick Owens:
The Morgan-Owens Latin Lexicon is found under the link entitled "adumbratio". The link entitled "silva" is a mere collection of other modern Latin dictionaries. If a term appears in the "silva" but not in the "adumbratio" it is because it has been intentionally rejected on philological grounds.
In the adumbratio, Morgan too went with sclopetum for a long gun and pistola for a short one, though I suspect fistula is better.
For "firearm" the only thing I've seen is manuballista, which is a little too broad; it's the word the Romans used for the hand-held version of the ballista, a siege engine—so essentially a crossbow. If you're willing to include crossbows in your definition of "firearms" then manuballista is actually perfect.
John C. Traupman uses sclopetum for both "gun" and "rifle" in his Conversational Latin for Oral Proficiency and Bantam New College Dictionary, but gives no entry for "pistol."