HB01,
You are correct that the 9.3x72R S&S used a lighter bullet, which I believe weighed about 186 gr.My Sauer sxs combination gun wouldn't stabilize bullets longer than the 286 gr RN bullet.When I started shortening the 74mm cases to 72mm,I found that old production Speer 250 grain bullets are shorter than the 286 gr,even though they are spitzer bullets. They shoot fine in my rifle.I have some of the new production bullets (270gr), but have not tried or measured them.Since I was only dealing with one barrel,my challenge was not nearly as great as yours.
Mike