The terminology in use in the 1700's was all over the place, which is one of the reasons Samuel Johnson put together his famous dictionary...to try and standardize things. In his 1768 edition he says a fowling piece is a gun used to hunt birds, and that a musket is a hand gun used by soldiers. A pistol is defined as a small hand gun used by soldiers. Of course that was England, not necessarily the way things were termed here. In November 1756 Sir William Johnson of NY (head of the Indian Dept) ordered the following:
400, Neat Fowling pieces Barrels 4 Feet Long SubstantÃal Stocks
400, d°. a better kind distinguish'd as above.
200, d°. 3 Feet Barrell for Boys. d°. Wilson Maker
He also ordered tons of shot, 8 tons of lead bars, and "100, doz". of BuIIet Molds for the before Mention'd Arms". Papers of Sir William Johnson, Vol. 2, p. 898.
This leads me to think that these guns for the Indians would have been more lightly constructed than military muskets and would have had no provision for bayonets. While a fowling piece is perhaps "optimized" for shot, it seems to me that the inclusion of bar lead and 1200 bullet molds means that Johnson and the Iroquois intended at least some of these fowling pieces to shoot round balls....at the French and their Indian allies...F&I war going on at the time and all....and SWJ in charge of the Indian units.