I in no way am being sarcastic or rude but if you look after the barrel properly you won't have misfires. I have 3 pedersoli's, 2 of which have the patent breech you mentioned, I've had one misfire and it was 100% on me.
Make sure you clean it well, and then before use run a dry patch down to get out some of the oil, squirt some isopropyl alcohol in the flash hole bore facing down and then run another dry patch which will pull alcohol through to remove the remainder of the oil. Shouldn't have an issue.
Edit: forgot to mention popping a cap after running your patch can also work.
You can run a 243 or similar brush down into the patent breech to loose the fouling but if you just draw up water and force it out hard through the breech end it does a good enough job.
I wouldn't have taken my hawken hunting dangerous game earlier this year if I had any doubt about it firing when needed. Didn't skip a beat.
I had actually ordered a hunter but changed my order to a Missouri River. Glad I did but I'm confident the hunter would have been a great gun too.