Many years back,I started using fillers.Long story short,I now use only Dacron(could substitute Kapok,both being of the same family).I hear cream of wheat is also good for the purpose but adds a lot more weight than polyester fiber(aejecta weight,filler and powder weight must be added to projectile weight and jacks up felt recoil).Tissue paper in my experiences doesn't work.
I use filler mostly with powders that are position and/or temperature sensitive.Since I shoot only cast bullets,please take into consideration that my velocities are quite low(from 1100 to 1600fps,I do not hunt exept round paper bullseyes that are way too far and small as I grow older).
For example,when I found that my 2400 load in my 30-30 was starting to group vertically when the temp went down(below freezing point),some gents on Cast Bullet Association pointed me towards using a magnum primer and some filler.Presto!groups were round again.
In another case(my 38-55),I was able to cut my 100 yds groups by 50% just by using Dacron filler.On the other hand,I never use it with easy to ignite powders(Titegroup)that are not position sensitive but do so with some others depending of which is used in which cartridge(700X in .308 needs it).And yes,might slightly increase pressure as I found with my 38-55 load using 4198. but just use common sense and keep an eye open on the posssibility and nothing serious should happen.Of course,if you load at hunting velocities with powders that nearly fill the case,do not use fillers,period.
So yes,I believe in filler but only under specific circumstances.And if you are a beginner,I'd say wait to gain some experience as to what signs are to be considered as warnings...just like I don't venture into duplex loads.Just don't feel confortable and knowledgable for it.Maybe one day....
