What type of powder to use?
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.
Powder Burn rates and Case Capacity
The concept is this, powder should fill 100% of the case space available and reach the SAAMI Standard Pressure at that point.
Powders that are too fast reach the pressure ceiling before filling 100% of the available space.
Powders that are too slow fill 100% of the space before reaching the SAAMI Standard Pressure.
In small cases like all three you mention, a little airspace is not critical with most powders. (Exceptions being some of the ball powders usually reserved for magnum loads anyway).
As cases get larger, this becomes more critical as powders that fill less than 65-70% of the case capacity can lead to SEEs or other strange phenomena where pressure spikes dramatically. With Rifle cases, and ball powders near perfect to slightly too slow is much more critical.
Having said the above, some powders (the faster pistol powders) tend to be comparatively immune to these phenomena and are used quite frequently in loading rifles with Cast bullets. (Reddot and Unique jump to mind)
To put it simply, with the three cartridges you are working with, I wouldn't waste time looking for the perfect combo for two reasons.
1.) It doesn't exist. You might get close, you wont get perfect and if by some miracle you do, you'll run out of that lot # of powder and the next one will be different.
2.) It doesn't matter anyway. If your loads are safe and function to your satisfaction, what else is there to achieve?
Good luck and safe shooting.
Wiljen