Originally posted by ezrunner
When fired by a human, all shot groups are a donut. The shooter
with the smallest donut wins.

Observationally, paint behaves the same, this is due to the
natural mechanics of the body.

Question: AGD/Tom.. or Glenn,

"Does a paintball marker, when held in a fixed mechanism, exhibit
this same tendency, or is there a pattern grouping that is somewhat
uniform over a reasonably large sample set?"

Yes, shooting from a firm and fixed hold on the barrel generates doughnut shaped shot patterns. The less spin the ball has when it enters the air stream, the smaller the doughnut.
If the balls leave the barrel with the seem either directly in line with or directly across the line of flight, the shot pattern tends to be more lineal in nature.