Contrary to a published recommendations, a friend occasionally unscrews the choke on his gun and shoots a round or two without any choke in the barrel, then reinstalls it like normal. Apparently with no damage. He's been doing this during our sporting clays shoot once a week for yrs.

Don, If you're comfortable with shooting without a choke in the barrel, I'd think that would tell if the choke machining in the barrel was the culprit. Just shoot it for POI at a closer range, say 20 or 30 yds.