Cool and Clean
You may get it ‘pretty close’ in four or five shots but it often takes a lot more. Very few rifles scopes have a true accuracy of consistent adjustments and thus going a bit and forth is not something unusual before getting it right. This is very okay as long as you take your time and you ensure that the barrel does not heat up too much. The moment you feel you are there, allow the barrel to cool completely then check it once again. Your best bet of getting the highest accuracy out of your rifle when sighting-in is cleaning it after a maximum of 20 shots. After you finish fire some trial shots to make sure that your sight-in is still maintained.