I have a CVA optima. Using pyrodex, tripple 7 or the white hot pellets my best groups at 100 yards were 3-4". I tried everything to improve those groups. Different bullets, different sabots, cleaning after every shot, not cleaning after every shot and nothing would bring the group size down to what I wanted. That was good enough for deer but I wanted better accuracy.
Heard good things about BH209, so I bought the CVA BH209 breach plug, brass powder flask, adjustable powder measure, BH209 powder, and Federal 209 primers. Using my favorite hunting bullet 240g Hornady XTP Mag with 100g by vol BH209, I get 1.5" groups at 100 yards with the bullet going out the muzzle at 1900fps. . I did have to play with the powder charge and type of sabot to get the best group.
Like MrBB, I use Powerbelt speed loaders in the field. They hold 3 tubes for bullet and pellets and 4 primers. I put 100g of powder in 2 of the tubes an put 2 bullets with sabots in the other one. With pellets you can load 3 shots because you can put the bullet in then the pellets on top in each tube. With the loose powder that doesn't work. I can still load in the field pretty fast I just have to dump the powder tube then get the tube with the bullets and dump one in. I have never had to use a followup shot on a deer though so speed has not been an issue in the field.
I thought loose powder would be a PIA but found that I like it better than the pellets. I will never go back to using pellets.