Welcome aboard. It is an old rifle and a Lightning is not a strong action in the first place. That said, I think you can probably find some loads using Unique or Trailboss that would work fine. I'm shooting an 1889 Swiss and a Colt Lightning pistol that was made about the same time with smokeless. I think I would err on the low side of the recommended loads or else use Pyrodex. You may wish to post this in the section on reloading to get more viewers.
