Cayuga D. Thanks for the input.

The shot that misfired was the first after cleaning with cotton patch and solvent. I did not have a tool to clean the breech but it was visibly clear (I could see daylight through it).

The pitting is so bad in my gun I think it is ruined. The pitting seems to be right around where the pellets were. I am wondering if I can get the bullet past the pitting by using 150 grains to make the load longer.