In the spirit of keeping on topic, one rule I apply after my sight-in process (unless it's a bull barrel) is to take a nice long break, then let off one more round to spot. This is in case the barrel loses zero when it warms up, and will be the (hopefully) kill round. Groupsspotted after this cold round are for load consistency only.

My well-versed brother taught me this, and I've seen it become significant (outside kill zone) after 150yds on some barrels.

Good luck.