You say they're 17th century stopes, but how certain are you about a) the age and b) whether they're a secure context?
On the first point, sometimes relatively modern workings were done using methods that were long outdated by miners of, shall we say, limmted resources that have the feel of something much older. As an example, there are some small levels in the Via Gellia with very small shotholes, of the size you'd expect from early 18th century powder work, and wooden tramways of the sort that the textbooks tell you are very early, but in fact they were driven a century or so later by particularly impoverished miners using small drills because they couldn't afford much powder or iron rails.
On the second point, if the workings you found this in are linked to workings of known later date, even if you've dug through a blockage to get in then you can't automatically assume this item is contemporary with the workings.
I have heard of tubular scoops being used to get powder into upwards shotholes and have a memory of seeing an illustration of one somewhere, but as Mr. Mike says, you wouldn't use iron for one because of the spark risk.
Follow the horses, Johnny my laddie, follow the horses canny lad-oh!