With patent breeches, the manufacturer often makes a smaller diameter hole in the back of the breech to hold the powder charge.If you have that in your gun, then you will need a small diameter bronze brush for cleaning that " chamber ", and a small diameter scraper to scrape the small wall at the back of that chamber. Typically, a 30 cal. rifle brush works in these and a scraper made for a .32 or .36 cal. gun does the cleaning chores. However, you have to measure these things, yourself, unless the factory tells you what you have. If you have a new gun, and didn't get a factory booklet that described the various parts of the gun, call the factory, They generally have an 800 number so the call is on their bill, not yours.
Not all percussion guns have this kind of ' chamber ", and some patent breech guns do not have them either. So, you need to know what brand and model you gun is, if you need help from us to tell you what you need, if anything. It is important to get the crud, and burned oil out of the chambers and flashholes in these guns for them to continue to finction properly.