I`m not sure if this is the proper forum for such questions, as it is more firearms-oriented rather than artillery, but i have seen some brilliant minds around that are knowledgeable in both fields and i suppose someone might have an answer.
I just took these photos of my finished 10cm M99 Austro-Hungarian shrapnel shell set (body, diaphragm and fuze).
My questions are the following:
1.) There is a difference in the remaining driving band groove width between the two projectiles (the left one is barely visible while the right one retains more of its original shape). I am assuming this is caused by the fact that, since these are not fixed ammunition, they were fired with different charges (left one with a higher/bigger charge) and the resulting higher pressure caused more deformation in the left band than on the right one. Am i correct in my judgement?
2.) I noticed some faint rifling marks on the centering band. They are present in just one section, approx. 1/4 of the circumference , and are present on just the left shell. I have also seen some in my 8cm shrapnel shell with a similar design (with copper centering band). It is obvious that from a mechanical point of view, they are caused by the shell not being perfectly coaxial with the barrel axis. But how exactly does this happen? Improper shell seating and centering in the chamber area? Barrel wear that causes misalignment mid-barrel?
I would be very interested in your replies!