I Hunter our Late ML Season with lotsa Snow and Cold & minus Wind Chills and never had a problem. Plus I leave My ACCURA loaded after the Hunt it goes from the Cold to the Warm Truck then to the Warm House then back to the Cold Truck in the Morning, then Warm Truck out into the Cold then back again.....Zero Problems.
I also cover the end of the Muzzle with a pice of Masking Tape, I have done this for years and Hunted in the Rain and Snow, Zero Problems. Many Times I have Hunted in the Rain for 3-4 Days straight with the same load in the ML and it fired just fine. The only thing I do is change my Primer after I come in from a Hunt and put a new one in each time I go out.
Try covering the end of the Muzzle.
(BP)