I shot 13.0 grains of HS-6 with that bullet. In the Brian Pearce article, 13.5 grains gets you 1101 FPS but I was getting 1140 with 13.0. 13.0 of HS-6 is a flame thrower also.
As for 2400, 18.0 grains was not that accurate in my gun, but 18.5 was very accurate with all shots touching, at least for the first string of shots. As the barrel leaded up, accuracy dropped. I have not chronied any of the 2400 loads but 18.5 grains of 2400 with the 270 SAA kicked more than 24.2 grains of IMR4227 with a 250 grain XTP. Also, I recall less leading with 18.0 grains of 2400 than with 13.0 of HS-6.
When I load some more ammo, I am going to drop back to 17.5 grains of 2400 to check leading and accuracy.