I gotta ask, are you sure you need a sinfully hard alloy? Automatically assuming you need a hard alloy for use in magnum pistols is an old wive's tale. It could be that your gun may shoot more accurately with hard versus soft lead, but not necessarily so. Proper fit of the bullet to the cylinder throats and the use of a premo lube will go a long way toward accuracy and non-leading. I should think a bhn (what's BCH?) of 15 should be dandy, and probably down to 10-12, too.
I always get a little chuckle when I hear guys talking about hardening their pistol bullets into the bhn 20's range without ever trying a "soft" alloy too. (Not guys here necessarily.
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