As a byproduct of the tests that Sam and I did with barrel strain with the 470 Nitro, we also discovered a vast difference in chamber pressures and internal ballistics concerning the two main type of fillers used to take up air space in the Nitro Cartridges.
The two fillers tested was Dacron and Foam. In two different loads, one with RL 15 and the other with IMR 4895, both cases the Dacron gave high pressures, along with inconsistency. While the Foam gave significantly lower pressures and gave excellent consistency.
Below is the actual Pressure Trace reports in pdf download format. Unfortunately on the one Dacron with RL 15 only one load was recorded. Given much higher pressure, inconsistency with RL 15 is not conclusive. Very interesting to look a the IMR 4895 load.