Let me restate what I don't think I communciated very clearly before: There is no guarantee of these loads working with mixed brass. Newberry looks for equal performance charge spans of at least 0.6 grains with his loads, and if you are shooting .223 Rem or some other round for which all brands of brass tend to have close or similar capacity, you may be just fine with one charge weight. But for .308 Winchester, the differences between brands are too great. You would need over 2.5 grains of Varget going from Lake City to Winchester to keep the same barrel time in the load I was looking at. That's way beyond the charge spans Newberry expects to achieve. Going from Lake City to Lapua .308 brass with the Varget load takes about 0.6 grains, so if I loaded at the high end of what I found with Lake City, the Lapua would just barely fall in with that same load being the low end of the span you would find developing the load in the Lapua cases. So the load might look good for both, but it won't leave much room for powder dispenser error. And it still won't hold up in Winchester.
You could get lucky and find something that works over a wider range than 0.6 grains. Hatcher tells of a coarse grain powder similar to IMR4320 that his arsenal loading equipment could only throw within an extreme spread of 1.7 grains for .30-06. Yet the ammunition loaded with it outperformed other, finer grain powders that could be thrown to within 0.6 grains on the same equipment. The coarse stuff wound up being the load for National Match ammunition the year he discovered it, and was used to set several records.
Good luck with it.
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