RE: Sighting a Scope on an Omega
What you propose is called " boresighting" . It is what we all did with centerfire HP rifles in the days before optical collimators came out! No reason why it shouldn' t still work! But I recommend firing your first shots after doing this at the same 25 yards to make sure you' re on paper,and go from there, whether you' re shooting a ML or a breech-loader.