WOW an ACCURA for a Pro, good deal! In My ACCURA's I shoot Pyrodox RS, 105 and 115gr's with 240gr XTP Mag's. Yes buying in bulk is the way to go. Corrosion should'nt be a problem if you clean as your suppos-to, as some ML's like certain pwoders and you should'nt sacrafice cleaning over a powder that your ML might like better. I have no experience with Blackhorn 209 in my ACCURA's, mabey someone else does? Success to you and let us know what you decide and how you make out.
(BP)