For a revolver, you can go as low as you want. Simply adjust to a faster powder as you move down in velocity.
For the ultimate low recoil, you want a light bullet and a low velocity.
If knocking over steel is not a requirement, a 180gn DEWC and a low charge weight of a fast powder like AA2, Solo 1000, or Bullseye would be good. If a lead bullet, I would avoid TiteGroup.