Do an internet search for “smokeless powder burn rates”, and several charts from various sources will show up as search fodder. Some of these charts show burn rates from only one manufacturer. Others show several manufacturer's powders. It can be interesting to see burn rate relationships between various powders.
CAUTION! At this point a stern word of caution is in order. If you closely examine and compare a few of these charts you will quickly realize that your favorite powder shows faster than another specific powder in one chart and slower in another. For example. Bullseye will be near the fast end of any chart it is listed on. However, it may be faster than powder “A” in one chart and slower than powder “A” in another. How can that be?
There are a lot of things that determine the burn rate of smokeless gun powder. The chemical composition, the shape, the surface area, the makeup and density of the powder coating, the temperature, and the pressure are a few of the variables. A big variable is the size of the container where the powder is burned. A given powder will burn differently in a 380 ACP (small) case than in a 460 Weatherby Magnum (large) case. I do not know how various burn rate chart producers generate their data and make their comparisons. It is apparent that the procedures and methods from chart to chart are different because the results are different. The fast powders will be on the fast end of the chart and the slow powders will be on the slow end. Closer comparisons will show powders in different orders from chart to chart.
WHAT DOES THIS MEAN TO THE RELOADER? It means that you are only safe when you use reloading data provided by a trusted powder or bullet manufacturer. What you MUST NOT DO is experiment with powders outside the bounds that are published and tested by the manufacturers. DO NOT assume that because powder “Y” has published data for your cartridge and bullet, that powder “X” which is next to or near it on a burn rate chart will also be good for that application.
The fact that you are interested in reloading or even reading this blog means that you are likely adventuresome and not afraid to wander into uncharted territory. In many areas of your life this inclination can be exciting and educational. In reloading or handloading, it can be dangerous or life threatening.
This explains why publishers ask you to start your load work ups at 10% below maximum but not less than 10%. Below 10% the results will not be linear and could be dangerous. Small case volume differences can have dramatic pressure differences. If you are looking for a reduced velocity load, for what ever reason, seek out and use published reduced velocity load data. Your reduced velocity load will likely require a different powder for the reasons mentioned.
Powder burn rate charts are interesting. They are not a substitute for reliable reloading data.