I have a load of 18 grains of Unique in my 270 Ruger # 1A using a 130 gr Nosler ballistic tip without any filler. the load is good for about 1,850 fps and inch groups at 100 yards. I don't believe in using a filler because if you don't get it right you have a second bullet to contend with and that ain't good.
my normal 45-70 fun load is also 18 grains of Unique with a 300 gr jacketed bullet nd that is also without any filler.
in either load there is quite a bit of room for the bullet and the chronograph does show any dramatic variations with either load