I shot the first flintlock rifle I made in the white, I just couldn't wait, just a few shots. I hadn't done the final the whiskering and sanding prior to my shots, I was careful with cleaning, no evil staining occurred, the rifle was finished with a darker aqufortis stain and Chambers oil finish. I had shot a flintlock before but had never built a gun, I just had to see if my creation would actually work, it did just fine.
Come to think of it, I shot my second build in the white as well, again out of curiosity as it was a walnut stocked fowler, another new one on me. In this case I had to see if the jug choke I had Caywood cut in the barrel made any difference, not much until I loaded the gun with a Skychief load long after the gun was finished and the shot pattern started looking like a swarm of bees.
I didn't feel the need to shoot any of my subsequent builds before they were finished, my curiosity had been satisfied by my first couple of in the white test runs.