The Germans, DWM and all had trouble deciding what spring to use.
This chart will give you some idea.
Though counter-intuitive, the .30 luger did not always use a "lighter" spring than the 9mm chambering; in fact the opposite is true in the
1906 American Eagle data. The 1920 and '23 models are shown as the same.
So, weaker may not be "better" in this case.
Be also sure your chamber is immaculately clean, just to confirm it is not a rough chamber, try a little oil on a couple rounds and see how that goes.