I was in the city for a few days this week and had the opportunity to swing into one of my favorite gunshops for some powder. I wanted an 8# keg of IMR 4064 but they'd sold the last one an hour before I'd gotten there. They offered me 8# Varget or IMR 4166 but I bought 4 single pounds of IMR 4064 instead. The salesman said to me, "You know, of course, that they're planning on discontinuing (IMR) 4064 as of March of 2016, right? They are making the IMR 4166 THE powder in that class because it's, you know, and Extreme powder, and it loads identical to 4064."
I asked him why IMR would discontinue one of their most popular powders in favor of the new comer, and no, it doesn't load the same. (Tho close; 4166 give about 3-5% higher pressures in say, 308, but with lower velocities than 4064) He said that I was wrong about the pressures and velocities and that their distributor had told him about the 4064 discontinuance.
I expressed my doubts but he stuck by his guns. I sent a text to my shooting buddy back home and he called IMR. They told him that they had no plans on discontinuing IMR4064 due to it's popularity.
So there you have it. Somebody isn't telling it straight.
If you shoot IMR4064 you might want to stock up? ~Muir