Stubble, you're correct... I was taught to make an adjustment only after firing atleast a 3 round shot group, and I practice this consistently. It would never do for me to fire one shot, and then make one adjustment. BUT, that is because I usually fire at a greater distance than 400 meters.
I never posted that I don't make any adjustments based on a single shot.I posted that I make rough adjustments only based on a single shot,and fine adjustments based only on a group.My main point was that it takes more than one or two shots to properly sight in any rifle.If I was handed in a rifle with a bore sighted scope, that I had to hunt big game with the next day,I could be reasonably comfortable after a seven or eight shot sight in,but not after only firing one or two shots out of that gun.