The question I have is on the use of case fillers. I have been, what I believe, successfully using Dacron fiberfill to offset the empty space in the case when loading reduced loads and cast bullets. This has enabled me to get complete ignition and good accuracy, respectable velocities, as well as reducing the concern for barrel leading at the resulting speeds.
I have used this philosophy on the 8mm Mauser, 303 Brit, 35 Whelen, and 45-70 cases with no clear indication of excessive pressures or concern. Perhaps I was lucky or perhaps there is some science to the percentage of load used and the use of the filler material.
In the paper written by Mr. C.E. Harris, on "Cast Bullet Basics for Military Surplus Rifles", he considers it strictly forbidden and briefly states it raises chamber pressure and contributes to chamber ringing.
I have been casting and handloading cast rifle bullets for over twenty years and many of the earlier writings I have used as technical knowledge had routinely used kapok, and other inert material to top off the powder charge to ensure proper ignition and uniform performance. While technology does advance and new information does condemn some of the old practices, I am a concerned about this report.
For example, in my 35 Whelen I have changed a very poor performer into a successful hunting load. I had experimented with using a Lyman 358315 w/w bullet, 204 gr., charged with 38.2 grains of IMR 4895. It gave me a calculated velocity of approximately 1,900 fps. The challenge was that the performance was very sketchy and inconsistent. After inspection and evaluation I noticed unburned lead particles left in the brass case. I quickly went to the rules of the past and took up that notable free space in the case with a case filler material. I noticed no indication of pressure change on the case or primer and from the human side, the charge felt no different on the shoulder. The performance outcome was just great and the load is now one of my main selections for that rifle. I get almost no barrel leading and I can punch consistent 100 yd holes.
While my success maybe a result of good fortune or perhaps a note to soften the condemnation of the use of filler materials. Considering Mr. Harris a well informed technical writer and validity of his statement, I would like to get comments and perhaps other technical reports on this topic. Let me know your views and experiences with this.