All kid's stuff22-250 with a fast twist barrel shooting heavies...
If you want to really raise dust and hit targets at very, very long range with cast boolits, bigger is better! 30 cals with 200 + grain projectiles and 45/70s with 405 grains boolits and bigger are the bomb.
Virtually unlimited range in photo one and 800 yards to the targets on the hill behind me in the second photo.