Oris - huh?
JERKY - not a bad theory, but I think that the barrel doesn't contract or expand enough to cause what you describe.
There are two reasons for changes in velocity at different temperatures. In cold weather, the air is denser and the bullet's velocity is slowed since it has to plow through, essentially, more air. But another reason is that smokeless powder will create less pressure at lower temperatures, less pressure = lower velocity. In the test Mikie related, the only important one is the powder/pressure one since it was a handgun and was probably measured close to the muzzle instead of 100 yds down range. Several things that could cause the reverse of what is expected are: were the tests conducted indoors or out? was the gun hot or cold when the tests were made? Also a 70 fps range isn't all that unusal even from the same lot of cartridges, so we may be wasting our time trying to figure out a non-puzzle.
Oh, and I just remembered one other thing - where were the tests conducted? Arizona? Yukon? Or if say, Australia, then that would explain it.
[This message has been edited by Mal H (edited November 21, 1999).]