For years I have been trying to uncover a quick and easy standard size group to evaluate my BP revolvers It was so simple that I'd been using it for years, a standard Playing Card! I have always wanted to put a cylinderfull into an Ace of Spades but usually inspite of my best efforts, the group gets spread out...
If you can hold one Playing Card at 21 ft, you are an offical gunslinger!
Centered on a standard sihoulette, it covers the heart perfectly!
Like they say sometimes you can't see the Forest for the trees, eh?