"I opened a new container of the same powder sub. and have shot seven in a row without a misfire. Maybe the original container is bad but I am told shelf life should not be an issue."
Shelf life isn't usually a major concern but sometimes even the slightest humidity can cause problems and to me that's what it sounds like you may be having a problem with the powder you used may have become contaminated by moisture from humidity..
Democracy is two wolves and a lamb voting on what to have for lunch.
Liberty is a well-armed lamb contesting the outcome of the vote.