Fouling Shot
A shot or two fired to season a freshly cleaned bore before it settles to its normal point of impact and shoots to its established zero.
A fouling shot is a round, sometimes two, fired through a freshly cleaned barrel to season the bore before any shot that needs to count. A spotless bore often throws its first round to a slightly different point of impact, because the bare steel grips the bullet differently than a lightly conditioned surface does. Putting a fouling shot or two downrange leaves a thin, even layer of copper fouling that brings the rifle back to its normal point of impact.
This is why a cold clean bore is treated as its own distinct condition, separate from the seasoned state most dope is built around. Shooters who log a cold-bore-shot carefully will note whether the bore was clean or fouled, since that single variable can shift the first round enough to matter. Firing a fouling shot first is the simplest way to make sure the rifle is holding its established zero before the real work begins.