I prefer Dacron. Pillow stuffing is cheap and readily available. I used to load cast bullets with pistol powder and filler, but it is very easy to double or triple charge w/o realizing it. The end result can be a blown up gun (ask me how I know this). I load .30-06 with a reduced load of W-748 and a Dacron filler. 150gr RNGC hard cast bullet at about 2100 fps. Not quiet but inexpensive.
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"Robo is right" Fuzzball