I always used 4198, either brand, .40 X original BP load = starting grains, then 'ease' up to regulate to sights. Always used dacron, I pull it from old pillows. Can't remember how many grains dacron. Don't cram it down into a brick, just soft and comfy like your pillow, but firm enough at the same time to be supportive. It's only there to take up room and keep the powder down. I've used this in everything from the .450, to the .450 no.2 Nitro (which takes an awful amount and ends up as fluffy snowball on the ground....literally in front of your elephant if that's the case), all the way to the .600
Since I had forgotten the grain-age of dacron in the .450, I just checked "Shooting the British Double Rifle", (second edition) and Ross Seyfried used up to 15 grains in the .450
It's fun weighing the little snowballs on the scale....pillow stuffing is my go-to stuff....
p.s.----remember, NO space between it and the bullet base....just takes up room, remember pillow-like. With other calibers, one can experiment on how many grains by feel and firmness.
....think I'll go rest on my pillow now....lol