Can you recommend a starting load with a 158 JHP pistol bullet in this cartridge?
Looking to use up a ton of Hornady XTP's and similar 158's while getting familiar with my new Henry lever rifle. I'm not hunting anything with this load; it is simply intended for muscle training and development of trigger process and familiarity with the rifle. I do not need speed here; for my purposes I just need a complete burning, safe load; anything between 800-1400 f/s out of the muzzle is just fine. I currently have H-4227, Unique, and H-4198 but if I need to buy a more appropriate powder, that's fine.
Thanks for the help.

I would use starting loads for the 357 Max (or 350 Legend) and go from there.