if that 6% [antimony? right??] alloy has been subjected to stress or pressure the BHN will be low.
if you melt and cast with it you will see close to 15 bhn air cooled.
I know it's confusing, but just because antimony is present it doesn't necessarily mean you will have a high BHN number.
also your alloy can vary slightly from batch to batch in final BHN numbers. [even if it is foundry certified]
so 1-2 BHN is meaningless,,,, it really is.
I try to keep my stuff in a window just in a window, remember that is the whole principle behind the Audette ladder test.
your looking for a window of powder loads that will give you the best chance of close-nuff being good enough for the rifle your shooting.