To get my guns sighted in, I start with a perfectly clean gun, pop 3 primers and swab the barrel. I then load the gun and fire the shot. The gun is then fully cleaned and start over for the next shot after it has cooled. This is the only way I have found that consistently gives me accurate feed back changes in my routine (scope adjustment, powder adjustment, change bullet, change sabot, etc...). This is the way I am going to load my guns for the actual hunt, so I want to be sure where that first shot out of a 3 primer popped barrel will hit consistently and accurately.
After I have completed the above routine, I will load on a dirty barrel to see how the Point Of Impact (POI) changes from the first shot. 90% of my shots are under 100 yards (most under 50) and the POI shift is minimal.
I like many here simply cannot leave a dirty gun, so popping 3 primers then dry swabbing cleans out the oils and puts my mind more at ease about not damaging my gun from leaving a dirty barrel.