Howdy Okie48,
I only use #11 caps, and I've never had an ignitionproblemusing Pyrodex P or APP fffg during winter weather.
I always place a rubber balloon over my muzzle secured by a rubber band to keep moisture out, and once the gunhasgoneoutside, I leave it in a cold hallway to keep condensation from forming in the barrel.
Although once,after shooting a deer using Pyrodex and whiledragging it out, it started snowing. And when the moisture from the snowcame into contact with the Pyrodex residue on the unblued muzzle crown of my rifle, it did stain the unprotected steel which never came out using solvent.
Pyrodex P does burn a little cleaner and packs into the breech tighter,producing a little higher velocity.Lately I'm onlyusing APP fffg duringDecember deer season in CT.