I have a HW in 30/40 Imp. It's also been throated and I have only shot it BSed with cast but, I also have a Krag with a Redfield #70, rear sight and the original front post.
I only tried one bullet in it, the 311413, using 4759. I tested loads from 18.5 - 20.0 and the 18.5 gr load gave me the best accuracy at 1.5", 5 shot group @ 100.
While I wouldn't recommend the 311413 bullet, I would recommend the older 311299 or the newer 314299. They both will cast ~.313 in 20/1. The new 311299 might also work, if the nose is at least .301. The 18.5 gr charge should work with that bullet, too and of coarse, use Rem 2 1/2 primers
Also, as a help to a aiming point, this is what I use, with the sight set about 3" high on a 6 o'clock hold. You can fold the bottom "V" to any width point that you want and fold, either on the 8.5 or 11" width. I fold it and staple on a clean backer, to get sighted in.
Frank