i Register
In some senses, musketoon is marked as obsolete, historical. Watch for register when choosing this word.
noun
A firearm, similar to a musket but with a shorter barrel and a large bore.
And d'Artagnan set the example. Then, turning toward Planchet, he made him a sign to uncock his musketoon. The Englishmen, convinced of these peaceful proceedings, sheathed their swords grumblingly.
One who is armed with such a musket.