SL,
That is the info I already looked at which is just the basics. I had talked to someone some time back at a SASS event that told me about the powder and that it was purposely made bulkier to help prevent overcharging of the cases. I'm still waiting on info from IMR but my memory of the conversation is that the max listed loads would come close to if not fully fill the case of the cartrdge making it dificult to imposible to double charge a case. In the example of a 45-70 this could mean that 14gr by weight may be a similar volumn to 70gr of BP. I realize that 70gr of BP is not going to have anywhere near the listed pressure in the chart for that 45-70 load but the volumn may be similar. Like I mentioned, I have requested more detailed info from IMR and will report back when and if they respond. As far as the make up of the powder I did not notice if it specified nitro or not but your probably correct on that. Then again, nitro based smokeless was the original BP substitute.