The .32 Win Special works pretty well with plain base cast bullets if you load it like a 32-40. Most cast bullets you can buy will probably be a little undersized and too hard for good accuracy. I don't have the rifle anymore, but I had a Marlin 336 in .32 Win Spl and it shot quite well with 170gr bullets cast in 20:1 alloy and 13.5gr of IMR-4227. Not a hunting load, around 1300 fps but pretty accurate. I'm sure Unique would have worked well too.
Chris.