As said a good 150-180 cast bullet moving 1.7K fps is all you need. This load is also easier on the shoulder, brass and rifle. The useful life of the rifle will be at least doubled if not more. I like around 16-17 grains of 2400 or 4759. No, there is no need for a filler. There is a number of good cast bullet designs for the 30-30.
By the numbers, I think 200 grain bullets are the sweet spot. From the 6" Glock, with Underwood ammo, which is loaded to original Norma specs, the 200 grain XTP bullet will start at about 1,300 fps. My question is... Would you roll with the XTP bullet or the WFNGC cast bullet.... Both are 200 grains @ 1,300 fps (1,250 fps from a G20)
Principal Purpose: Magnum shotshell loads, 10, 12, 16, 20 and 28 ga. Secondary Uses: Magnum handgun loads Remarks: Powder of choice for magnum hunting loads. Canister Sizes: View All Blue Dot ® Recipes. View the SDS
I also tested some 200 grain projectiles from a Noe mold (light blue) pushed by 11.7 grains of Accurate Arms#9.. It's a neat mold that will cast wide nose flat point or hollow point bullets flat point were used in this test. To test them, I used a Smith & Wesson 1026, a glock 20 with original factory barrel and a Ruger gp100 in 10mm.