20's were common when I grew up, though 12's were still most common. It was understood that you had to own a 12, and you did, but when it came time to shoot you took the 20.

There was the perception that the guys who used the 12 had an advantage....and that meant the rest of the guys could snicker at them when they missed a shot. On the other hand, there was nothing better than making solid hit with a 12, a display of firepower that seemed to put the 20 ga. guys in their place.

It was all part of the fun....