As long as some are comparing Blackhorn and Black Mag I thought I might add my @ cents worth. Blackhorn is a specialized powder made with nitrocellulose base With a small amount of the components of pyrodex added it is a progressive burning powder, Black Mag is a sugar based powder with a different formula and a moisture deterrent coating it ignites at 345 degrees which is the lowest of the subs and only 45 degrees more than the black powder at 300 degrees.It is not progressive burning.
For those who do not understand the difference between progressive burning and not.
Progressive burn is when a powder increases its rate of burn in reaction to rising pressure more potential energy can be released in a more timely manner this way so the pressure peak can be longer and lower and still get more velocity.
I tried to put a graph on that show the pressure levels many different powders are at when using 150 gr including Blackhorn but I can not get the page here to take my graphs.