[410-er]

Need more info.Gun,flint,etc.Possible crud pushed in breech area.

 

[410-er]

When you clean make sure you do it in a bucket of water and swirel the water in that breech area to clean it out.Often guys just use other stuff that gets pushed into the breech area and never gets removed.I don't put ANY oils of any kink in mine till after the season.When I do its olive oil.Any petrolium products make a tar in the rifling when burned.You can use petrolium based oils just be sure to clean before you fire.
Your TC is capable of 1 1/2" at 50yds so keep at it till you find the recipe.

 

[410-er]

You can also clean it out with your rifle cleaning rod and a 30cal brush.
I gotta agree,sounds like an oil problem.Wipe the frizzen and flint with alcohol then fingers off!