Re: 300 RUM berger 215gr hybrid load data ?
I would start out with about 87 gr of Retumbo and work up 1 gr at a time and expect to see max around 92-94.
The difference between Retumbo and H1000 is Retumbo is a slower burning powder which means you'll need more of it for a max load, which is a good thing. The closer you are to 100% case capacity you are, the better for more consistent combustion.
Also, I have always gotten slightly better velocities with Retumbo with about the same accuracy.
Both are good relatively stable powders.
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