Caliber is not the problem, rifling is.
A rifled gun makes a terrible shotgun'
I have spent years experimenting with muzzleloaders and modern guns with rifled barres and shot. .45 , .50, 58, 38, .22 .44. .45. calibers.
Nothing but a waste of time if your gun has rifling. Remove the rifling and you have a serious rabbit killer.
Bobby Hoyt will remove the rifling, but not on a CVA due to their breech plug design.