Well like someone else mentioned the likelyhood of a steady shot is very slim!
A off hand head shot in the twisted position offered from a tractor seat with open sights at 50 yards is a task. Add an unsteady platform and the odds that the one .22 bullet hits it's target gets even slimmer!
However a 3" 20 ga has 18 .24 diameter pellets that travle around 1100 fps! So it would be like you have 18 22LR rifles on the tractor with ya!
You would need to pattern the shotgun to see what choke tube works best in your shotgun.
You might also look at some BB and BBB loads! They are still close to the >22 size and they would allow you to launch even more rounds in the air!
And unless you are wanting to recover them, them running off to die keeps you from having to deal with them!
