Casey,
In my 70 F./zero test with RL-26, using the 150 Partition and a max charge, 26 actually gained around 50 fps.
My "zero" tests are actually at -5 to +5 degrees, which is as close as I can come to zero under actual outdoor conditions, given the vagaries of weather. This is explained in my chapter on temperature and powder in GUN GACK II, which includes a bunch of tests in cartridges from the .17 HMR to .375 H&H. In fact in the tests with Extreme, Enduron and RL-16 and 23 powders usually show around 25-30 fps difference in velocity from 70 to zero, sometimes plus and sometimes minus.
