I have over the years read several complaints that Blue Dot can go wild in high pressure loadings in Magnum rounds . I imagine that like all the other old Hercules powders there have been changes since Alliant took over . The new 2400 looks different and seems harder to ignite in low loads and Re-7 looks nothing like the older form .
I had trouble with carefully weighed charges or Blue Dot in 357-44 B&D it would shoot very well then one shot would be way over pressure so way back in the 1980's I stopped using it in high pressure cartridges . I do like Blue Dot in 12 gauge & .45 acp thogh I have recently found WW-571 / HS7 works a bit better .