The Clays series stopped shipping because ADI had a fire that destroyed the drier used in their AP series. I don't know the cause of the fire, but if it was something to do with the manufacturing process, that would be a good reason to change that process.
It is not uncommon for powder manufacturers to change suppliers to make a powder to a particular specification. But it doesn't usually come out exactly the same when they do. Accurate had a warning up when they were no longer able to source Nitro 100 from the same supplier, and now have Nitro 100 NF (New Formulation) and had to put all new load data together for it. QuickLOAD has no powder models for the IMR SR series or 700X or 800X because, Hartmut Broemel (QuickLOAD's author) told me they have changed these powders frequently enough in the past that no model he could include would accurately cover what some handloaders still have in stock from the past, so he considers it unsafe.
I expect ADI will do a good job of working out the new substitutes and that they will likely burn cleanly, too, as that was a big element of their popularity. What Hodgdon will do about a naming convention, I don't know. They might even keep the old names. That would be unfortunate if it happens, but it might explain the denial that the powders will be phased out.
Hodgdon has also denied that GD is making IMR powder process changes. I'm now inclined to take that with a grain of salt.
Clays, incidentally, is not like Bullseye. It's faster. It's closer to Vihtavuori N310 and Norma R1 in burn rate. Like those other two powders, the charge weights needed to reach a particular pressure are lower than they are for Bullseye, so please don't try a swap out of one for the other. With 230 grain ball in .45 Auto, it takes 4 grains of Clays to reach about the same pressure 5 grains of Bullseye does. The resulting velocity is lower because less total gas quantity is being made.
