I left my Endeavor loaded, complete with primer, outside over night. It was fifteen degrees. No hangfire and impact was exactly as it was in eighty degree weather. I left all the loading components outside too. Just shot the two shots. It was one inch at 100 yds. The sabot was quite a bit harder to load when it was cold. I was shooting 100 gr 209 with 200 gr SW. cci primer. regular, not magnum. I don't know what could cause your hangfires. I am on my third jug. No hangfires. Also worked up a load with a friends Omega. Shot most of a jug, no problems. He was is Alaska hunting and didn't have time. He shot a Dall sheep, Grizzly, Wolverine, and Wolf. Had a good hunt.