RE: best load for rabbits?
If you are jump shoting them where the are running away from you I like #4. In a .410 1/2-3/4oz, 20ga 7/8-1oz, or 12ga 1-1 1/8oz. with a improved cylender choke. Any standard load low or high brass will work.
With dogs where there running at you #6 with which choke is best for where you are hunting