I saw a write up on these somewhere that now I can't find my way back to it which is of no help to you other than to know that there is something out there.
I just started working with R26 in my 6.5 Sherman yesterday and it seems it may be a good fit. Speeds with 140gr A-Max approaching 3300. It is the same chemistry as R17 and R33. When I move up to the 160's I'll be able to make a direct comparison to R33.
the Atk statement says reloader 26 has a burn speed between rl22 and rl 33, it also says it is definitely slower than reloader 25, but then Alliants reloading data for the 7mm & 300 wheatherby has the max loads at about 4 gr less than the reloader 25 loads with a little more velocity than rl 25 so is it slower or faster than rl 25 or is it both????