No, there definitely was no drilling of barrels before ca. 1430, a time when they were mounted first with hooks, but not yet wrought integrally.
As I wrote, I surmised that both the Berne gun and my barrel were drilled out somewhen in their later working life, which may have been during the 15th century.
As you know I have a Nuremberg wrought iron haquebut barrel which cannot have been made before ca. 1490/1500 but the inner surface of which has never been drilled! Not only is it of totally irregular 'bore'
at the muzzle but one can look inside and see heavy distortions going on down to the rear! The only ammunition it could have possibly fired would be some kind of shot ... I am sure you recall seeing it in my collection when you were here in August.
Attached please find images. It is the second last in the first pic and the one on the right in the row of muzzles.