My experience with W296 is that it is not too consistant.That is, five shot groups ran up to, or even over, an extreme spread of 100 fps. In a 7 1/2 inch Ruger Super Blackhawk with the Keith bullet weighing 265 grains I got 1358 average with 24.5 grains, and a spread of 96. Another group, same charge, gave 1323 and 103 spread.
Going down to 22 grains of W296 gave 1188 with 96 spread.
20 grains gave 1126 with 198 spread.
For heavy loads, 2400 powder gave more power was much more consistant. The absolute maximum load is 22 grains and that gave me 1415 with a spread of 68.
I loaded 2400 down, 20 grains gave 1312 and 41 spread.
17.5 grains gave 1120 with 45 spread.
and down at 15 grains it was 965 and 105 spread. Obviously too low a charge for efficiency.
To use all those plated bullets you could get W231. It is a very fast powdeer for the 44 magnum and extreme care must be used to prevent a double charge. A maximum load is only 8.2 grains of W231, and that gave me a velocity of 1018, with an extreme spread of only 17 fps. Thus, it should be very accurate and easy to shoot, but a double charge would turn the gun into a hand grenade.
If you buy powder for those bullets, a good choice would be Unique and not as touchy as W231.