The bullet was seated properly; I have a mark on my ram rod that I use to gauge this. I shot two primers before loading but I did forget to swab the barrel. The first shot did go off so I assume that would cancel out any misfires due to oil or moisture? The powder sub is a year old and has been stored inside the house and dry.
I contacted the powder sub. manufacturer and was told my flash hole may need cleaning with a drill bit. I had a spare breech plug that was brand new, so I screwed it in and the first shot fired. Second shot misfired. 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.
The same combination of gun, powder, bullet, and primer worked flawlessly last year for twenty plus shots.
You seem to be addressing your own concerns, all if which may be the root of the problem. if the powder was a year old then can't we asume it went bad for some odd reason thus causing the problem? If contaminated powder isn't the problem then I don't know what else to blame it on.