Over the years what we call a particular gun has changed.
Musket originally referred to an extra heavy two man gun that operated as flank protection on a battlefield. While not a fast shooter it covered what a SAW is used for on today’s battlefield
It evolved in to the one man smoothbore bayoneted gun, then in to the rifled pieces.
It was once the cock that carried a flint, and the hammer the frizzen.
Rifles were screw bores.
Fusil was French guns, and fusil today is often a shotgun.
The British northwest gun, trade gun was called by Americans a London Fuze in writings of the time.
Generally on this forum we say fusil to mean a French civilian gun or a civilian smoothbore in flintlock that has a long barrel and heavier construction.
Fowling gun a light fusil.
A smoothbore built on a rifle platform is a smooth rifle or rifle mounted fusil
Roll your eyes at this point.
We try to be all technical but red is red and not to be confused with scarlet or ox blood, and red isn’t pink, ( a word that wasn’t invented yet) and the Red Coats could have their reddish orange of the infinity or the deep red of the officers
If you see fusil on this forum think context
If you have sinus problems you could have a runny nose, a cardiac arrhythmia or stuff falling out of your riflemans shirt