I TRY TO ALWAYS dry any oil out of a bore and chamber before firing a round. However, that said, it is entirely possibel (LIKELY, EVEN!!) that your first shot from a clean barrel will perform differently than succeeding ones. Col. Townsend Whelen used to talk about what he called "the sniper's zero", by which he meant that a rifle should be zeroed so the first shot from a clean or cold barrel would be the one that hits dead on, because this first shot is not only the most important one, it may be your ONLY one!! Where I have been hunting recently, in the Adirondacks, this idea certainly applies!!