I don't have my info with me but my memory is close enough...
In 2003 I worked up new loads for a pair of my 270W's with 150gr Partitions. Velocity was about 60-70fps faster with RL22 compared to my tried and true loads with H4831. Accuracy was as good as before. Then I read more and more about the temp sensitivity of RL powders.
I had fired a goodly number of my final loads through my chrono that previous summer and always note the temp when I chrono.
So the following winter, I put of batches of the same ammo and both rifles in the back of the truck to "cold soak" overnight when the temps were down to about 5 degrees.
Early next morning I went to the range. I parked the truck tight along the shooting bench (we can do that in the middle of the winter at my range) so I could keep the Oheler timer in the cab and warm. At shooting time the temps ran 9-14 degrees.
I also borrowed a Fluke temp "gun" from a friend (I gotta get me one of those). I kept the ammo in the shade and I would fire two rounds and let the rifle sit outside in the shade to cool while I shot the next rifle, letting the rifles thouroughly cool each time.
Short story: From summertime data derived at 89-99 degrees, one rifle GAINED about 12fps, the other rifle lost about a 100fps in the cold weather--go figure. More importantly, my ES in one rifle opened to 86fps, the other 104fps. This is from summertime ES of <25fps for both rifles/loads.
All of this data was derived from 10 shot strings--something I think is important when getting serious about ES, average velocity, measuring pressure with Ballistics Lab or Pressure Trace.
This is consistent with info from some whose knowledge I have faith in. The temperature sensitivity is as much about inconsistenty from shot to shot as it is about velocity loss.
Accuracy was not nearly as good, but at least some portion of that can be attributed to chattering teeth
I went back to H4831. At a tad under 2900fps with a 150gr, the 2950+ I gained with my 270W's wasn't enough be concerned about. I would not be surprised though to see a lot of variation with different cartridges, loads, and even different firearms.
I have read, and have one friend, who is claiming phenomenal velocity with RL22 in their 30-06's. I would really like to see what is happening in really cold temps.
Obviously, Only a small segment of big game hunters hunt in temps near or below zero.
I have been thinking about trying RL in my 30-06AI's. But I WILL test the load in cold weather (I mean really cold) before I would officially designate it a hunting load.....
Casey
