Thanks for all the replies!
I plan to switch to Pyrodex. I only used Shockley's square sticks cause that is all that was left at the gun shop right in season. Also will switch to muzzleloader primer caps - I would suppose they burn hotter than regular reloading primer caps I was using.
Interesting comments on blackpowder vs. pellets. Sounds like powder is more accurate. And I think the round 777 pellets are better than the square sticks I used.
The muzzleloader specific primers are mild. In cold weather I would use a regular strength 209 primer such as Win209, Rem STS, CCI.