Modern high power rifle shells do not need fillers to work. At least not as long as the powder-fill is at least 85% to 100% and above, which is a compressed load. Most powder now a days is not position sensitive.
Older black powder cartridges like the 45/70 usually run at 50% powder-fill, then a filler can make a difference on the plus side for accuracy and better/closer extreme spreads.
Fillers used today are; Dacron used to give quilts their fluff, and kapok which is used in life preservers. Since both are fluffy and weigh very little for the volume they occupy, the don't raise pressures much, if at all.
The more people I meet, the more I love my dog
They're going to get their butts kicked over there this election. How come people can't spell and use words correctly?