Bill308
You never said what your rifle is. Myself, i have never experienced a hang fire in -0 temperature with Omega, or modified CVA. The Triumph did hang fire a couple of times, but it was brief, so brief one couldn't have backed away from the scope. However, i did fix that.
A good breech plug won't hang fire in sub zero temperatures, i don't think. Myself, i don't use magnum primers. Make CVA breech plug look like Omega breech plug, and they don't hang fire. QRBP modified, don't hang fire. The made for Blackhorn QRBP shouldn't hang fire, but i cannot say for sure, with out having ever using one.