Im not the most technical shooter, but I can prove this article is BS rather easily. Drop a modern shell into your classic double (assuming it is safe to shoot) and pull the trigger. Doesnt feel very good, does it? Now, drop in a low pressure RST shell. Feels sweet, doesnt it? Its that simple. One feels like crap. The other does not. The rule I follow is this, I shoot an old gun with the closest thing to the ammo it was made to shoot. The end.