ronlaughlin,
My rifle is a TC Omega with the older style breech plug that is supposed to be good for BH209. It apparently is good, because I've never had an issue with 100's of rounds. I must have had condensation. Or, maybe it wasn't completely dry from the day it rained.
It's good to know that cold alone isn't the issue. Some years the season has a lot of below zero weather.
Bill