USARO4,
I have recently heard talk about ringing chambers too and I've been loading ammunition for over 30 years.
I have never used a filler. I won't bore you with the quantity of loadings with reduced loads of 15 grains or less in 30-06, 308, 7mm TCU, 30-30 and 444 Marlin and many more. I've used cast bullets with most reduced loads. My loads shoot minute of angle out to two hundred yards and minute of Ram at 500 meters in a French Mas 1936.
The problem that I've had with reduced loads is double charging the cases with powder. That is exciting and I have two rifles that have met their demise with that scenario.
To solve that problem, I have developed loads with Reloader 7, IMR 4759, AA 5744 and IMR 4227 that if doubled, the bullet will not fit in the case.
I still have several loadings that I very carefully load with 9.2 grains of IMR 7625 and a 444 Marlin with 14 grains of that powder too. I load 9.5 grains behind a Saeco #316 (150 grain) 30-30 bullet for my 30-30 10" TC and the accuracy out to 300 and 400 meters is incredible.
Harold