I wouldn't rely on just one shot for the data. I have seen guns throw a wicked good pattern and then the next two shots be just so-so, or, vis-a-versa. Dirty bores and chokes vs. clean also can make a difference. Shotguns can be some finicky sumbucks at times.

Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats.