See, that is the kind of information that should be posted. Do you have any info on actual temperatures versus velocity for the different powders? What i would like to see is the same type of info that is on the Hodgdon web site showing velocity for temperatures ranging from 100 F to at least 20 F. If you start talking about variation for constant temperature that is an entirely different ball game, and you are talking SD and SE for nearly constant temp, which depends more on your particlular rifle and the laod it likes, though there is some truth in stating that some powders on average have lower SE for the accuracy load. I by no means argue. I am a metallurgical engineer who must dispute theories for a living.
"Buzzards gotta eat, same as worms" - Josey Wales
Just a couple musings on temp enduced velocity variations...
After I get a load that is doing well at whatever the ambient air temp is, I test for accuracy while shooting over a chrony at 5 different temps
1. 4 degrees, the temp of my refrigerators freezer
2. 40 degrees, the temp of my refrigerator's top shelf.
3. Ambient air temp... whatever that is, preferably 72 [img]/ubbthreads/images/graemlins/grin.gif[/img].
4. Whatever temp the ammo reaches when I keep it in contact with my body under clothing for an extended period of time, about 80-85 degrees.
5. 127 degrees, the temp of my hot tap water, seperated from the ammo by a ziploc bag
You can keep the temp stable at any of those temps for several minutes, by using the ziploc in water technique,Just dont mess around on the way to the chrony, and remember to remove the rounds one at a time so they don't get a chance to warm/cool different than their bretheren. I usually do 5-8 rds per temp, about 25-30 total.
When I put this test data along side the info I have from developing the load, ive got a pretty good idea of what to expect under any circumstance.
Just my .02
eh... some might argue over whether my test sample is large enough to make difinitive conclusions, but ive got some data. So far all ive tested is h414, h4831, h4831sc, and h1000, all in 300WM. Ive tested the three slowest powders with either 200SMKs or 220SMKs, with the H1000 being the most stable, followed by the H4831sc, then h4831. H1000 was consistant to within 10fps across the board, probably within my margin of error. The twin 4831s gained 25fps, and 33fps respectively. The H414 was tested under 110gr Vmax. It showed a 60 fps gain from bottom to top. Im not saying its a bullet proof testing system, but its easy, cheap, and anybody can do it. You can get a lot more data from a quick and dirty test than all the pondering in the world.
I went through the same thing you are going through. I had a factory 300 wm and through hours of range time RL22 came out on top. As a matter of fact the others didnt compare. I used norma brass w/75 gr of 22 and 180 SST. I am having a custom rifle built in a 300 wm and will start with RL22. We will see what happens. Good Luck [img]/ubbthreads/images/graemlins/wink.gif[/img]