the unburnt powder is due to not reaching the pressure needed for a full burn.
there are a couple of ways to correct this.
in my 44 mag with 2400 it was to use a magnum primer to raise the pressure initially.
coincidentally in my 45 colt with the same load and a 10 grain heavier boolit the mag primer was not needed.
in my 357 a tighter neck tension was needed for full burn.
but loading density is a consideration to factor in, especially in an autoloader where the powder it tossed back and forth in the case.
you can verify a powders sensitivity with a chronograph,simply by just tilting the bbl down or up before each shot.
i know it makes a difference.
as far as the right powder some are just softer shooting and easier on the gun.
example is unique versus titegroup in a 45 acp.
the velocities are the same[ the unique was more consistent] but you can feel the recoil difference between them and see it on the boolit deformation.
this is also one application where unique doesn't seem to burn dirty must be a good combination of pressure and case filling.