how to tell if you need a pressure point under barrel

[jpx2rk]

Slip a few business cards between the barrel and the stock forend. It will change the POI but will give an idea if a PP is needed. Its how I initially discovered my 270-08Imp shot better with than without.
Bill

Is this a "trial & error" method where you will need to move the business cards around, or leave them at a "tight spot"? Just curious about the steps to try this method.