Dutch guns

What I would like to be able to do is to look at a Dutch gun's shot weight and the weight of the piece, in Amsterdam pounds, and be able to estimate the gun weight. I have an idea that might not be too easy. I imagine that guns were probably not cast to the ideal thickness of metal, but were both lighter and heavier than that. We would also need to take into account that a gun was a drake or klokwijs (with a bell-shaped chamber). You also have guns that were "metael" or "ijser" (bronze or iron).