Many of the fillers, such as you make reference to, are bulk, dacron type filler used for making and stuffing pillows, available in fabric stores. Most usually the filler is a weighed quantity of this bulk filler for uniformity.
Personally, I prefer to use polyester quilt batting that comes in several different thicknesses if a filler is absolutely necessary (most times it isn't). Using the quilt batting, it comes in a uniform thickness, so cutting uniform squares of this batting results in very uniform performance in a load, and the density is more predictable than the bulk dacron type fillers. On bottleneck type cases, crochet hooks (also available in fabric stores) of various diameters are about the perfect tool for seating these polyseter squares into the case atop your powder charge.
Keep in mind that you can overdue just about anything, and a little filler goes a long way. The whole idea is to keep the powder charge down against the primer in reduced loads for consistent iginition.
Hope this helps answer some questions.
God Bless,
Marshall
Personally, I prefer to use polyester quilt batting that comes in several different thicknesses if a filler is absolutely necessary (most times it isn't). Using the quilt batting, it comes in a uniform thickness, so cutting uniform squares of this batting results in very uniform performance in a load, and the density is more predictable than the bulk dacron type fillers. On bottleneck type cases, crochet hooks (also available in fabric stores) of various diameters are about the perfect tool for seating these polyseter squares into the case atop your powder charge.
Keep in mind that you can overdue just about anything, and a little filler goes a long way. The whole idea is to keep the powder charge down against the primer in reduced loads for consistent iginition.
Hope this helps answer some questions.
God Bless,
Marshall