Thanks for putting that up - a very interesting study.
I'm currently writing up my IMR-4166 findings as part of my H4895 alternatives feature, and it is a strange (and in my view) not entirely successful powder. At least in the 223 with 77gn bullets, that is. Overall, results can be very good, but it ends up short on MVs. Looking at IMR 'Enduron' powders' loads for various cartridges in reloading manuals, there is definitely a trend there, especially for 4166 and 4955. As a result, most competition shooting users won't regard them as suitable alternatives for H4895, VarGet, and H4831/4831sc especially. Handloader magazine found similar results too in their tests.
This may be academic anyway as Hodgdon has withdrawn the entire range of five powders for 'production difficulties'. There is a definite lack of mention among potential users though, which makes me wonder how well they sold prior to their removal even in a time of powder shortages.
The other odd thing about 4166 was that when I researched 223 loads data, only Hodgdon itself offered any. Lyman No.51 has added it since for a few heavier bullet weights. Both Hodgdon and Lyman data gave very low maximum charges and also very low MVs in this application compared to its neighbours in burning rate charts, and this for a modern powder with it's said ~10% nitroglycerine content. It also appears to be lacking in the claimed enhanced temperature stability from the above exercises in your link. (The PRS people said very early on that 4451 wasn't a patch on H4350 in this regard too.)
