I went to a range yesterday and it was a very humid day. It was raining terribly bad all morning, cloudy through the rest of the day and raining again at night... Obviously I was shooting in between rain periods, but it was very humid day.
I have spitfire and was shooting Shockley 3F powder.
Out of 20 shots each, Remington caps had 2 or 3 slow fires (with a second delay - bum-bang), but no misfires. CCI Magnums produced 3 or 4 slow fires and 1 misfire. I'll finish up CCI magnums, but in the future would try to buy Remington caps if available.