Is your magneto speed bayonet mounted on your barrel while using your calculator? The weight of the bayonet will change your impact points on paper. I don’t know just guessing.
Nice, I’m in the same boat as you. Looking for a smaller rifle for elk and deer. I’m in the process of putting together a 7saum. I have short action, dies, barrels been ordered. I just can’t find any brass. Norma or adg.