ok, i guess im just talking in theories here too, I have no actual data to prove any of this, but heres my opinion. I would think the differences between f/l and n/s casings would be so small, (probably talking in the .003-.001 range, or the thickness of a piece of paper) that other inconsistencies in your process (i.e. one grain of powder here or there or differences in primers from one to another) would probably make it very hard to tell. I just think there are so many things that are not able to be repeated every shell exactly that the difference would be unnoticable. Just my opinion, I guess the only way to tell is to try it!!