My conclusion is that I am not confident in the velocity data I generated (gotta take the plunge for the Lab Radar). However, I do suspect that SW Precision Rifle powder is more temperature sensitive (at least in this application) than the manufacturer suggests. Shooters World tends to emphasize the use of PR rifle powder for the heavier bullets in 5.56 such as the 77gr which may result in better ES.
I will keep working with it to see what I can learn.
Temp stability of powders have become a "thing" among handloaders (long range shooting has been a big reason) in recent times. A lot of powder manufacturers are now making that claim. My experience, and shooting with friends is that despite the claims their are a lot of powders out there that may be less sensitive to temperature than in the past but still exhibit temp sensitivity to some degree.
