I threw together a load last winter with CFE223 and it shot amazing with little testing, this summer shooting the same load the groups were very poor. I haven't done any testing to find out what was going on, if I was really trying to figure it out I would down load the CFE a little in the summer and test if that was the problem, but for whatever reason, there was a large difference.

If you're not familiar with CFE223 (Copper Foiling Eraser), CFE can perfectly also represent Carbon Fouling Explosion, it's messy powder. Sometimes I do some shooting with my AR and leave the gun loaded, left loaded for a couple days and the top rounds in the magazine start to tarnish from whatever they put in the powder to cut down on copper fouling.

Not to say CFE223 sucks, if I can get it to shoot year round how it was shooting last winter I would put up with it's downfalls, because it was doing great.

Here in MN I shoot if it's -25 or 95+, the best powders I have used and been consistent year round have been from Hodgdons extreme powder line. IMR has come out with their equivalent "Enduron" powder line that's supposed to be pretty good with temperature stability also but I haven't tried any yet.