PB can be a great target load powder in revolver rounds.
Back about 20 years ago I embarked on a program to find the
lowest power .44 load that would shoot holes touching groups
and still get the bullet down range. I didn't get a stuck bullet
as I chickened out going below 700 fps.
The load is 4.5gr. of PB over a 240gr Keith type SWC lubed
in one shoulder. I always use an inert material/buffer to fill
up those big cases and hold the powder against the primer.
Clean and consistant as the previous post says. Maybe a touch
more work but it's fun work!
I have used Grex shotgun buffer as well as used up polishing
compound both corn and walnut. It all works fine. The Grex leaves
a thin film of plastic in the bore which lubricates it. The polishing
compounds slowly polish your bore especially the walnut.
The burning walnut also smells a little like a hippy party. Older guys
at the range may look at you funny

I gave up on the walnut
and use Grex now.
You should load enough buffer to create a slightly compressed
round. The buffer compresses fine. The whole idea is to hold the
powder in one place.
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Nemo