I did drop down on the titegroup to 10grs.
I used the 310 cast bullet from TII bullets.
At 25yds I got a one hole from 5 shots from a 500 JRH. I found this same load to be accurate, out of my 500S&W, but not as good as the BFR in 500JRH. A couple of notes, one is different twists in barrels. S&W 1-18
BFR uses 1-15.
Brass is 500S&W cut down to 1.400
Primer pocket is for Large Rifle. With the Titegroup I used a Mag Pistol primer. Otherwise I still use a LR or Lrg mag rifle primer.
While not quite as mild as the 310 Cast, I loaded some Sierra 350gr that I had on hand.
Using 13grs of Longshot turned out to be a nice surprise. Tried 2 shots and they were touching at 50 yds. I know I should have loaded at least 5, but didn't.
I usually have more cast on hand. Right now just heavier 405gr and higher.