yards is no distance to try and determine the accuracy potential of a pistol or any particular ammunition. It is just too close. I don't know what type of bullseye competition you are thinking of entering, but it isn't going to be shot at 21 feet.
If you want to try and find out what store bought ammunition is the most accurate out of your pistol you need to shoot very carefully from a sandbag off of a bench at at least 25 yards, and then 50 yards. One of your brands will prove to shoot a tighter group.
"A Liberal is someone who doesn't care what you do, as long as it's mandatory". - Charles Krauthammer
Great advice! Also a specific manufacturer ammo load that proves to be most accurate for one shooters gun may not be the case for another shooter. IMO it would not suprise me if Speer Lawman was among the most accurate for most pistols as far as FMJ ammo.