Hi everybody. I have had a dillon RL550 press for about 15 years. I have made tens of thousands of rounds with good results 99% of the time. However I still feel like I'm guessing when it comes to powder type. Can anybody suggest a good book on the subject? I've serched Amazon and none of the titles suggest what I'm looking for. Let me be more specific. I load 9 mm, .40 S&W, and 45 ACP using the same powder for all three. I've been told this isn't wise in spite of the fact that the tables have loads for all three using the same powders. I have some understanding of how slow and fast burning powder work. But it is still a little vague why one is appropriate for 45 ACP and a different one is more right for 9 MM. Either the name of a good book on the subject or any comments would be greatly appreciated. Chuck.