Ottoman bulbous barel wall musket

[Oliver Pinchot]

Great find, Eftihis.
It retains most of the characteristics of the Catalonian guns from which it is derived. This form of muzzle is called "lale" (la-LEH) or tulip. Most barrels were heavily reinforced at breech and muzzle to keep them from exploding in use; past a certain point, it simply became stylistic. Persian, Indian, and other barrels often show this trait as well (or similarly, a substantial flare, with or without some sort of animal or monster head.)

Please show a pic of the right side of the butt all the way up to the lock.